Acute Basilar Artery Occlusion 

Health / By

Acute Basilar Artery Occlusion 

Description

  • acute basilar artery occlusion is a subtype of ischemic stroke, most commonly due to atherosclerosis and embolism(1,2)
    • accounts for about 1% of ischemic strokes and up to 10% of large vessel occlusions
    • basilar artery is part of the posterior cerebral circulation

Epidemiology

Incidence/Prevalence

  • reported annual incidence 4/100,000 persons in the United States(2)
  • reported to account for about 1% of ischemic strokes and up to 10% of large vessel occlusion strokes(1)

Risk Factors

  • potentially modifiable or addressable risk factors for ischemic stroke, including acute basilar artery occlusion, include
  • see also
    •  Cardiovascular Disease Major Risk Factors
    • Risk Factors for Stroke or Transient Ischemic Attack

Etiology and Pathogenesis

Causes and Pathogenesis

  • most common causes(1,2)
    • atherosclerosis
    • embolism from heart or proximal artery
  • less common causes include(2,3,4)
    • arterial dissection
    • giant cell arteritis, inflammatory vasculitides, and other vasculopathies
    • meningitis and other infections or their complications
  • symptoms of ischemic stroke are due to reduced cerebral perfusion and resulting impaired function and eventual infarction
    • impaired function may be reversible if circulation restored in time
    • oxygen depletion leads to depleted energy available to neurons and supporting cells, leading to impaired signaling and anoxic depolarization and subsequent excitotoxicity
    • Reference – Am J Med 2021 Dec;134(12):1457
  • some symptoms may be associated with site of tissue infarction, but clinical manifestations can vary greatly(2,3)
    • pontine infarction associated with quadriplegia, hemiplegia, dysarthria, dysphagia, and/or horizontal gaze paresis
    • mesencephalic and thalamic infarction associated with impaired consciousness, quadriparesis, oculomotor dysfunction, and behavioral abnormalities
    • damage to cranial nerves, parts of pontine, and/or parts of midbrain nuclei associated with cranial nerve dysfunction
    • damage to corticospinal tract associated with quadriparesis or hemiparesis
    • brain stem involvement associated with “crossed signs” such as unilateral cranial nerve involvement and contralateral hemiplegia

Posterior Circulation Anatomy

  • posterior circulation involves vertebral arteries, basilar artery (which arises from vertebral arteries), and their branches supplying blood to posterior brain including
    • brain stem
    • thalamus
    • cerebellum
    • occipital lobes
    • portions of temporal lobes
  • vertebral arteries
    • typically arise from subclavian arteries; sometimes arise directly from aortic arch
    • ascend through transverse foramina of the cervical vertebrae
    • luminal diameter typically ranges from 3 to 5 mm
    • each vertebral artery includes 4 segments:
      • V1 (pretransverse segment): origin point to transverse foramen of C6
      • V2 (transverse segment): transverse foramen of C6 to transverse foramen of C2
      • V3 (suboccipital segment): transverse foramen of C2 to atlanto-occipital membrane
      • V4 (intracranial segment): atlanto-occipital membrane to pontomedullary junction where they join to form the basilar artery
    • intracranial branches:
      • posterior spinal artery – supplies inferior cerebellar peduncle
      • anterior spinal artery – supplies lower medulla and spinal cord
      • posterior inferior cerebellar artery – supplies lateral bulbar region, the posteroinferior cerebellar hemisphere, and the inferior portion of the vermis
  • basilar artery forms where vertebral arteries join at pontomedullary junction
    • travels rostral/anterior along medulla and pons and then diverges to form posterior cerebral arteries
    • branches:
      • anterior inferior cerebellar artery – proximal basilar artery to supply inferolateral pons and anteroinferior cerebellum
      • pontine arteries – supply several portions of pons
      • superior cerebellar artery – from distal basilar artery to supply upper pons, midbrain, and superior cerebellum
      • posterior cerebral artery – from distal termination of basilar artery to supply midbrain, hypothalamus, and thalamus; further branches include posterior temporal artery, internal occipital artery, calcarine artery, and parieto-occipital artery, supplying different portions of cerebrum
  • Reference – Neurol Sci 2019 Oct;40(10):1995

History and Physical

Clinical Presentation

Basilar Artery Occlusion

  • basilar artery occlusion may present with(1,2,3,4)
    • impaired consciousness (comatose state reported in about 40% of cases)
    • cranial nerve dysfunction including
      • bulbar symptoms such as facial palsy, dysarthria, anarthria, dysphagia, and aphagia
      • oculomotor dysfunction
    • motor symptoms including weakness, with hemiparesis or quadriparesis in severe cases
    • behavioral abnormalities
  • onset can be either(1,2)
    • sudden/apoplectic (associated with embolic etiology)
    • insidious/progressive/stuttering over hours-to-days (often associated with atherosclerotic etiology)
  • determining precise time of symptom onset can be more difficult than for anterior circulation strokes as diagnosis may be delayed due to nonspecific symptoms and variable onset(1)
  • prodromal symptoms may occur days-to-weeks before disabling symptoms(1,4)
    • commonly
      • headache
      • nausea
      • vertigo
    • other
      • ataxia
      • double vision
      • drop attacks
      • dysarthria
      • dysphagia
      • dysequilibrium
      • facial paresis
      • hearing loss
      • hemiparesis
      • hemisensory loss
      • impaired consciousness
      • jerking, shaking, or convulsions
      • paresthesias
      • pathological laughter (“fou rire prodromique”)
      • tinnitus
      • vision loss
      • visual hallucinations (peduncular hallucinosis)
      • yawning
  • tools commonly used to evaluate suspected stroke such as Face Arm Speech Time (FAST) and National Institutes of Health Stroke Scale (NIHSS) are not as accurate in patients with basilar artery occlusion as they are in patients with anterior circulation stroke(1,2)
  • establish time of symptom onset to inform management decisions
    • time of stroke onset is typically when patients were last at their previous baseline or symptom-free state
    • if patient cannot give this information, time of onset is when patient was last awake and symptom-free or “last known well”
    • time of onset is particularly important for
      • thrombolytic therapy (may be indicated if ischemic stroke onset ≤ 4.5 hours previous)
      • endovascular therapy (may be indicated if ischemic stroke onset ≤ 6 or 6-24 hours previous, depending on imaging studies)
    • for details related to ischemic stroke in general see
      • Acute Ischemic Stroke
      • Thrombolytics for Acute Stroke
      • Endovascular Therapy for Acute Stroke
  • basilar artery occlusion may lead to(2)

Cerebellar and Posterior Cerebral Artery Territory Ischemic Stroke

Cerebellar Stroke
  • potential serious complication is cerebral edema within the posterior fossa
    • may compress brain stem and/or obstruct the fourth ventricle and cause hydrocephalus
    • typically manifests as reduced consciousness within 1-7 days of infarction
    • managed with surgery; osmotic diuretics such as mannitol or hypertonic saline may suffice in mild cases
  • common initial symptoms can be non-specific, including dizziness, nausea and vomiting, altered mental status, and vertigo
  • some symptoms are associated with particular vascular territory affected
    • posterior inferior cerebellar artery (PICA) territory
      • PICAs supplied by vertebral arteries before they join at the basilar artery
      • supplies cerebellum, sympathetic nerves, brainstem (5th, 10th, and 11th nuclei), and spinothalamic tract
      • symptoms include
        • Wallenberg syndrome (dysarthria, ipsilateral limb ataxia, vertigo and nystagmus)
        • ipsilateral Horner syndrome, pharyngeal and laryngeal paralysis, and facial pain and temperature sensation loss
        • contralateral limb and trunk pain and temperature sensory loss
    • anterior inferior cerebellar artery (AICA) territory
      • AICAs supplied by basilar artery
      • supplies cerebellum, sympathetic nerves, brainstem (5th, 6th, and 7th nuclei), and spinothalamic tract
      • symptoms include
        • ipsilateral limb ataxia, Horner syndrome, facial weakness, lateral gaze paralysis, and facial pain and temperature sensory loss
        • contralateral limb and trunk pain and temperature sensory loss
    • superior cerebellar artery (SCA) territory
      • SCAs supplied by basilar artery
      • supplies cerebellum, midbrain (3rd nucleus), and spinothalamic tract
      • symptoms include gait and limb ataxia, ipsilateral Horner syndrome, and contralateral pain and temperature sensory loss
  • References – Clin Med (Lond) 2023 May;23(3):219, Stroke 2014 Feb;45:e56
Posterior Cerebral Artery Stroke
  • Posterior Cerebral Arteries (PCAs) supplied by basilar artery
  • supplies several brain areas, including
    • midbrain structures, choroid plexus, and posterior thalamus
    • red nucleus
    • superior cerebral peduncles
    • portions of temporal lobe
    • occipital lobe including visual cortex
    • splenium of corpus callosum
  • symptoms may include
    • Weber syndrome – ipsilateral 3rd nerve palsy, contralateral hemiplegia
    • Benedikt syndrome – ipsilateral 3rd nerve palsy, contralateral extrapyramidal signs
    • Nothnagel syndrome – ipsilateral 3rd nerve palsy, cerebellar ataxia
    • Claude syndrome – ipsilateral 3rd nerve palsy, contralateral extrapyramidal signs, and cerebellar ataxia
    • ataxia if superior cerebellar peduncle involvement
    • chorea (or hemiballismus) and hemisensory disturbance
    • problems naming colors and objects
    • homonymous hemianopia
    • alexia without agraphia
  • Reference – Clin Med (Lond) 2023 May;23(3):219

Assessment Scales

National Institutes of Health Stroke Scale (NIHSS)

  • note that NIHSS and other tools commonly used to evaluate suspected stroke are not as accurate in patients with basilar artery occlusion as they are in patients with anterior circulation stroke(1,2)
  • NIHSS
    • The National Institutes of Health Stroke Scale (NIHSS) has a total score range of 0 to 42 points, with higher scores indicating greater symptom severity.
      • An NIHSS score > 22 points at presentation indicates severe symptoms and an increased risk of complications.
      • Severity is based on assessments of consciousness, gaze, visual fields, facial palsy, limb motor function and ataxia, somatosensation, language, dysarthria, and attention.
      • See the table for descriptions of individual items and scoring.

Table

Table 1: National Institutes of Health Stroke Scale (NIHSS)

Procedure*Scale Definition
1a. Level of consciousness: investigator must choose a response if full evaluation is prevented by such obstacles as endotracheal tube, language barrier, and/or orotracheal trauma/bandages; 3 is scored only if patient makes no movement (other than reflexive posturing) in response to noxious stimulation0 – alert; keenly responsive1 – not alert; but arousable by minor stimulation to obey, answer, or respond2 – not alert; requires repeated stimulation to attend, or is obtunded and requires strong or painful stimulation to make movements (not stereotyped)3 – responds only with reflex motor or autonomic effects or totally unresponsive, flaccid, and areflexic
1b. Level of consciousness – questions: patient is asked month and their age; answer must be correct – there is no partial credit for being close; aphasic and stuporous patients who do not comprehend the questions will score 2; patients unable to speak because of endotracheal intubation, orotracheal trauma, severe dysarthria from any cause, language barrier, or any other problem not secondary to aphasia are given a 1; it is important that only the initial answer be graded and that the examiner not “help” the patient with verbal or nonverbal cues0 – answers both questions correctly1 – answers 1 question correctly2 – answers neither question correctly
1c. Level of consciousness – commands: patient asked to open and close eyes and then to grip and release nonparetic hand; substitute another 1-step command if hands cannot be used; credit is given if unequivocal attempt is made but not completed due to weakness; if patient does not respond to command, task should be demonstrated to them (pantomime), and result scored (that is, follows 0, 1, or 2 commands); patients with trauma, amputation, or other physical impediments should be given suitable 1-step commands; only first attempt is scored0 – performs both tasks correctly1 – performs 1 task correctly2 – performs neither task correctly
2. Best gaze: only horizontal eye movements tested; voluntary or reflexive (oculocephalic) eye movements will be scored, but caloric testing not done; if patient has conjugate deviation of the eyes that can be overcome by voluntary or reflexive activity, score will be 1; if patient has isolated peripheral nerve paresis (cn iii, iv, or vi), score 1; gaze is testable in all aphasic patients; patients with ocular trauma, bandages, preexisting blindness, or other disorder of visual acuity or fields should be tested with reflexive movements, and a choice made by investigator; establishing eye contact and then moving about patient from side to side will occasionally clarify presence of partial gaze palsy0 – normal1 – partial gaze palsy; gaze is abnormal in 1 or both eyes, but forced deviation or total gaze paresis is not present2 – forced deviation, or total gaze paresis not overcome by the oculocephalic maneuver
3. Visual: visual fields (upper and lower quadrants) tested by confrontation, using finger counting or visual threat, as appropriate; patients may be encouraged, but if they look at side of the moving fingers appropriately, this can be scored as normal; if unilateral blindness or enucleation, visual fields in remaining eye scored; score 1 only if clear-cut asymmetry, including quadrantanopia, found; if patient blind from any cause, score 3; double simultaneous stimulation performed at this point; if extinction, patient receives 1, and results used to respond to item 110 – no visual loss1 – partial hemianopia2 – complete hemianopia3 – bilateral hemianopia (blind including cortical blindness)
4. Facial palsy: ask (or use pantomime to encourage) patient to show teeth or raise eyebrows and close eyes; score symmetry of grimace in response to noxious stimuli in poorly responsive or noncomprehending patient; if facial trauma/bandages, orotracheal tube, tape, or other physical barriers obscure face, these should be removed to extent possible0 – normal symmetrical movements1 – minor paralysis (flattened nasolabial fold and/or asymmetry on smiling)2 – partial paralysis (total or near-total paralysis of lower face)3 – complete paralysis of 1 or both sides (absence of facial movement in the upper and lower face)
5a. Left motor arm: limb placed in appropriate position; extend arms (palms down) 90 degrees (if sitting) or 45 degrees (if supine); drift is scored if arm falls before 10 seconds; aphasic patient is encouraged using urgency in voice and pantomime, but not noxious stimulation; each limb tested in turn, beginning with nonparetic arm; only in case of amputation or joint fusion at shoulder, examiner should record score as untestable, and clearly write explanation for this choice0 – no drift; limb holds 90 (or 45) degrees for full 10 seconds1 – drift; limb holds 90 (or 45) degrees, but drifts down before full 10 seconds; does not hit bed or other support2 – some effort against gravity; limb cannot get to or maintain (if cued) 90 (or 45) degrees, drifts down to bed, but has some effort against gravity3 – no effort against gravity; limb falls4 – no movementUntestable – amputation or joint fusion (provide explanation)
5b. Right motor arm (same procedure as 5a)0 – no drift; limb holds 90 (or 45) degrees for full 10 seconds1 – drift; limb holds 90 (or 45) degrees, but drifts down before full 10 seconds; does not hit bed or other support2 – some effort against gravity; limb cannot get to or maintain (if cued) 90 (or 45) degrees, drifts down to bed, but has some effort against gravity3 – no effort against gravity; limb falls4 – no movementUntestable – amputation or joint fusion (provide explanation)
6a. Left motor leg: limb placed in appropriate position; hold leg at 30 degrees (always tested supine); drift scored if leg falls before 5 seconds; aphasic patient encouraged using urgency in voice and pantomime, but not noxious stimulation; each limb tested in turn, beginning with nonparetic leg; only in case of amputation or joint fusion at the hip, examiner should record score as untestable, and clearly write explanation for this choice0 – no drift; leg holds 30-degree position for full 5 seconds1 – drift; leg falls by the end of the 5-second period but does not hit bed2 – some effort against gravity; leg falls to bed by 5 seconds, but has some effort against gravity3 – no effort against gravity; leg falls to bed immediately4 – no movementUntestable – amputation or joint fusion (provide explanation)
6b. Right motor leg (same procedure as 6a)0 – no drift; leg holds 30-degree position for full 5 seconds1 – drift; leg falls by the end of the 5-second period but does not hit bed2 – some effort against gravity; leg falls to bed by 5 seconds, but has some effort against gravity3 – no effort against gravity; leg falls to bed immediately4 – no movementUntestable – amputation or joint fusion (provide explanation)
7. Limb ataxia: this item aimed at finding evidence of unilateral cerebellar lesion; test with eyes open; in case of visual defect, ensure testing done in intact visual field; finger-nose-finger and heel-shin tests performed on both sides, and ataxia is scored only if present out of proportion to weakness; ataxia is absent in patient who cannot understand or is paralyzed; only in case of amputation or joint fusion, examiner should record the score as untestable, and clearly write explanation for this choice; in case of blindness, test by having patient touch nose from extended arm position0 – absent1 – present in 1 limb2 – present in 2 limbsUntestable – amputation or joint fusion (provide explanation)
8. Sensory: sensation or grimace to pinprick when tested, or withdrawal from noxious stimulus in obtunded or aphasic patient; only sensory loss attributed to stroke is scored as abnormal and examiner should test as many body areas (arms [not hands], legs, trunk, and/or face) as needed to accurately check for hemisensory loss; score of 2, “severe or total sensory loss,” should only be given when severe or total loss of sensation can be clearly demonstrated; stuporous and aphasic patients will, therefore, probably score 1 or 0; patient with brain stem stroke who has bilateral loss of sensation is scored 2; if patient does not respond and is quadriplegic, score 2; patients in a coma (items 1a-3) are automatically given a 2 on this item0 – normal; no sensory loss1 – mild-to-moderate sensory loss; patient feels pinprick is less sharp or is dull on the affected side; or there is a loss of superficial pain with pinprick, but patient is aware of being touched2 – severe-to-total sensory loss; patient is not aware of being touched in the face, arm, and leg
9. Best language: a great deal of information about comprehension will be obtained during preceding sections of examination; referring to the last few pages of NIHSS 2022 Jul 25 PDF, patient is asked to describe what is happening in picture, to name the items on the naming sheet, and to read from list of sentences; comprehension judged from responses here, as well as to all of the commands in the preceding general neurological exam; if visual loss interferes with tests, ask patient to identify objects placed in hand, repeat, and produce speech; intubated patient should be asked to write; patient in coma (items 1a-3) will automatically score 3 on this item; examiner must choose a score for the patient with stupor or limited cooperation, but a score of 3 should be used only if the patient is mute and follows no 1-step commands0 – no aphasia; normal1 – mild-to-moderate aphasia; some obvious loss of fluency or facility of comprehension, without significant limitation on ideas expressed or form of expression; reduction of speech and/or comprehension, however, makes conversation about provided materials difficult or impossible; for example, in conversation about provided materials, examiner can identify picture or naming card content from patient’s response2 – severe aphasia; all communication is through fragmentary expression; great need for inference, questioning, and guessing by the listener; range of information that can be exchanged is limited; listener carries burden of communication; examiner cannot identify materials provided from patient response3 – mute, global aphasia; no usable speech or auditory comprehension
10. Dysarthria: if possible, adequate sample of speech must be obtained by asking patient to read or repeat the following words: mama, tip-top, fifty-fifty, thanks, huckleberry, and baseball player; if patient has severe aphasia, clarity of articulation of spontaneous speech can be rated; only if patient is intubated or has other physical barriers to producing speech, examiner should record score as untestable, and clearly write an explanation for this choice; do not tell patient why they are being tested0 – normal1 – mild-to-moderate dysarthria; patient slurs at least some words and, at worst, can be understood with some difficulty2 – severe dysarthria; patient’s speech is so slurred as to be unintelligible in the absence of or out of proportion to any dysphasia, or is mute/anarthricUntestable – intubated or other physical barrier (provide explanation)
11. Extinction and inattention (formerly neglect): sufficient information to identify neglect may be obtained during prior testing; if patient has severe visual loss preventing visual double simultaneous stimulation, and cutaneous stimuli are normal, score is normal; if patient has aphasia but does appear to attend to both sides, score is normal; presence of visual spatial neglect or anosognosia may also be taken as evidence of abnormality; since abnormality scored only if present, item is never untestable0 – no abnormality1 – visual, tactile, auditory, spatial, or personal inattention or extinction to bilateral simultaneous stimulation in 1 of the sensory modalities2 – profound hemi-inattention or extinction to > 1 modality; does not recognize own hand or orients to only 1 side of space

Citation: * Administer stroke scale items in the order listed. Record performance in each category after each subscale exam. Do not go back and change scores. Follow directions provided for each exam technique. Scores should reflect what the patient does, not what the clinician thinks the patient can do. The clinician should record answers while administering the exam and work quickly. Except where indicated, the patient should not be coached (for example, do not make repeated requests to patient to make a special effort). Note the time the stroke scale was administered and the interval since stroke onset or last known well, such as, baseline, 2 hours post treatment, 24 hours post onset, 7-10 days post onset, or 3 months post onset. For scoring: add the individual scores for each item. Total score range is 0-42 points, with higher scores indicating greater symptom severity.Reference -National Institute of Neurological Disorders and Stroke (NINDS) 2023 JunePDF

Table

Table 2: Posterior National Institutes of Health Stroke Scale (POST-NIHSS)

Procedure*Scale Definition
1a. Level of consciousness: investigator must choose a response if full evaluation is prevented by such obstacles as endotracheal tube, language barrier, and/or orotracheal trauma/bandages; 3 is scored only if patient makes no movement (other than reflexive posturing) in response to noxious stimulation0 – alert; keenly responsive1 – not alert; but arousable by minor stimulation to obey, answer, or respond2 – not alert; requires repeated stimulation to attend, or is obtunded and requires strong or painful stimulation to make movements (not stereotyped)3 – responds only with reflex motor or autonomic effects or totally unresponsive, flaccid, and areflexic
1b. Level of consciousness – questions: patient is asked month and their age; answer must be correct – there is no partial credit for being close; aphasic and stuporous patients who do not comprehend the questions will score 2; patients unable to speak because of endotracheal intubation, orotracheal trauma, severe dysarthria from any cause, language barrier, or any other problem not secondary to aphasia are given a 1; it is important that only the initial answer be graded and that the examiner not “help” the patient with verbal or nonverbal cues0 – answers both questions correctly1 – answers 1 question correctly2 – answers neither question correctly
1c. Level of consciousness – commands: patient asked to open and close eyes and then to grip and release nonparetic hand; substitute another 1-step command if hands cannot be used; credit is given if unequivocal attempt is made but not completed due to weakness; if patient does not respond to command, task should be demonstrated to them (pantomime), and result scored (that is, follows 0, 1, or 2 commands); patients with trauma, amputation, or other physical impediments should be given suitable 1-step commands; only first attempt is scored0 – performs both tasks correctly1 – performs 1 task correctly2 – performs neither task correctly
2. Best gaze: only horizontal eye movements tested; voluntary or reflexive (oculocephalic) eye movements will be scored, but caloric testing not done; if patient has conjugate deviation of the eyes that can be overcome by voluntary or reflexive activity, score will be 1; if patient has isolated peripheral nerve paresis (cn iii, iv, or vi), score 1; gaze is testable in all aphasic patients; patients with ocular trauma, bandages, preexisting blindness, or other disorder of visual acuity or fields should be tested with reflexive movements, and a choice made by investigator; establishing eye contact and then moving about patient from side to side will occasionally clarify presence of partial gaze palsy0 – normal1 – partial gaze palsy; gaze is abnormal in 1 or both eyes, but forced deviation or total gaze paresis is not present2 – forced deviation, or total gaze paresis not overcome by the oculocephalic maneuver
3. Visual: visual fields (upper and lower quadrants) tested by confrontation, using finger counting or visual threat, as appropriate; patients may be encouraged, but if they look at side of the moving fingers appropriately, this can be scored as normal; if unilateral blindness or enucleation, visual fields in remaining eye scored; score 1 only if clear-cut asymmetry, including quadrantanopia, found; if patient blind from any cause, score 3; double simultaneous stimulation performed at this point; if extinction, patient receives 1, and results used to respond to item 110 – no visual loss1 – partial hemianopia2 – complete hemianopia3 – bilateral hemianopia (blind including cortical blindness)
4. Facial palsy: ask (or use pantomime to encourage) patient to show teeth or raise eyebrows and close eyes; score symmetry of grimace in response to noxious stimuli in poorly responsive or noncomprehending patient; if facial trauma/bandages, orotracheal tube, tape, or other physical barriers obscure face, these should be removed to extent possible0 – normal symmetrical movements1 – minor paralysis (flattened nasolabial fold and/or asymmetry on smiling)2 – partial paralysis (total or near-total paralysis of lower face)3 – complete paralysis of 1 or both sides (absence of facial movement in the upper and lower face)
5a. Left motor arm: limb placed in appropriate position; extend arms (palms down) 90 degrees (if sitting) or 45 degrees (if supine); drift is scored if arm falls before 10 seconds; aphasic patient is encouraged using urgency in voice and pantomime, but not noxious stimulation; each limb tested in turn, beginning with nonparetic arm; only in case of amputation or joint fusion at shoulder, examiner should record score as untestable, and clearly write explanation for this choice0 – no drift; limb holds 90 (or 45) degrees for full 10 seconds1 – drift; limb holds 90 (or 45) degrees, but drifts down before full 10 seconds; does not hit bed or other support2 – some effort against gravity; limb cannot get to or maintain (if cued) 90 (or 45) degrees, drifts down to bed, but has some effort against gravity3 – no effort against gravity; limb falls4 – no movementUntestable – amputation or joint fusion (provide explanation)
5b. Right motor arm (same procedure as 5a)0 – no drift; limb holds 90 (or 45) degrees for full 10 seconds1 – drift; limb holds 90 (or 45) degrees, but drifts down before full 10 seconds; does not hit bed or other support2 – some effort against gravity; limb cannot get to or maintain (if cued) 90 (or 45) degrees, drifts down to bed, but has some effort against gravity3 – no effort against gravity; limb falls4 – no movementUntestable – amputation or joint fusion (provide explanation)
6a. Left motor leg: limb placed in appropriate position; hold leg at 30 degrees (always tested supine); drift scored if leg falls before 5 seconds; aphasic patient encouraged using urgency in voice and pantomime, but not noxious stimulation; each limb tested in turn, beginning with nonparetic leg; only in case of amputation or joint fusion at the hip, examiner should record score as untestable, and clearly write explanation for this choice0 – no drift; leg holds 30-degree position for full 5 seconds1 – drift; leg falls by the end of the 5-second period but does not hit bed2 – some effort against gravity; leg falls to bed by 5 seconds, but has some effort against gravity3 – no effort against gravity; leg falls to bed immediately4 – no movementUntestable – amputation or joint fusion (provide explanation)
6b. Right motor leg (same procedure as 6a)0 – no drift; leg holds 30-degree position for full 5 seconds1 – drift; leg falls by the end of the 5-second period but does not hit bed2 – some effort against gravity; leg falls to bed by 5 seconds, but has some effort against gravity3 – no effort against gravity; leg falls to bed immediately4 – no movementUntestable – amputation or joint fusion (provide explanation)
7. Gait, trunk, and limb ataxia: assessment for signs of unilateral cerebellar lesion; test performed with eyes open; in case of visual defect, ensure testing performed in intact visual field; finger-nose-finger and heel-shin tests performed on both sides, and ataxia scored only if present out of proportion to weakness; ataxia is absent if patient cannot understand or has paralysis; in case of amputation or joint fusion, examiner should record the score as untestable, and clearly write rationale for this choice; in case of blindness, perform test by having patient touch nose from extended arm position; instruct patient to stand with feet together and eyes open for a few seconds and then walk naturally; if no signs of gait/trunk ataxia, ask patient to walk in tandem; if patient unable to walk due to limb weakness, assess trunk ataxia by assessing trunk control with patient in sitting position0 – absent1 – present in 1 limb2 – present in 2 limbs3 – patient cannot walk or maintain sitting position without assistance; retro and/or lateropulsion. broad-based gait, and increased sway of body can be presentUntestable (UN) – amputation or joint fusion (provide explanation)
8. Sensory: sensation or grimace to pinprick when tested, or withdrawal from noxious stimulus in obtunded or aphasic patient; only sensory loss attributed to stroke is scored as abnormal and examiner should test as many body areas (arms [not hands], legs, trunk, and/or face) as needed to accurately check for hemisensory loss; score of 2, “severe or total sensory loss,” should only be given when severe or total loss of sensation can be clearly demonstrated; stuporous and aphasic patients will, therefore, probably score 1 or 0; patient with brainstem stroke who has bilateral loss of sensation is scored 2; if patient does not respond and is quadriplegic, score 2; patients in a coma (items 1a-3) are automatically given a 2 on this item0 – normal; no sensory loss1 – mild-to-moderate sensory loss; patient feels pinprick is less sharp or is dull on the affected side; or there is a loss of superficial pain with pinprick, but patient is aware of being touched2 – severe-to-total sensory loss; patient is not aware of being touched in the face, arm, and leg
9. Best language: a great deal of information about comprehension will be obtained during preceding sections of examination; referring to the last few pages of NIHSS 2022 Jul 25 PDF, patient is asked to describe what is happening in picture, to name the items on the naming sheet, and to read from list of sentences; comprehension judged from responses here, as well as to all of the commands in the preceding general neurological exam; if visual loss interferes with tests, ask patient to identify objects placed in hand, repeat, and produce speech; intubated patient should be asked to write; patient in coma (items 1a-3) will automatically score 3 on this item; examiner must choose a score for the patient with stupor or limited cooperation, but a score of 3 should be used only if the patient is mute and follows no 1-step commands0 – no aphasia; normal1 – mild-to-moderate aphasia; some obvious loss of fluency or facility of comprehension, without significant limitation on ideas expressed or form of expression; reduction of speech and/or comprehension, however, makes conversation about provided materials difficult or impossible; for example, in conversation about provided materials, examiner can identify picture or naming card content from patient’s response2 – severe aphasia; all communication is through fragmentary expression; great need for inference, questioning, and guessing by the listener; range of information that can be exchanged is limited; listener carries burden of communication; examiner cannot identify materials provided from patient response3 – mute, global aphasia; no usable speech or auditory comprehension
10. Dysarthria: if possible, adequate sample of speech must be obtained by asking patient to read or repeat the following words: mama, tip-top, fifty-fifty, thanks, huckleberry, and baseball player; if patient has severe aphasia, clarity of articulation of spontaneous speech can be rated; only if patient is intubated or has other physical barriers to producing speech, examiner should record score as untestable, and clearly write an explanation for this choice; do not tell patient why they are being tested0 – normal1 – mild-to-moderate dysarthria; patient slurs at least some words and, at worst, can be understood with some difficulty2 – severe dysarthria; patient’s speech is so slurred as to be unintelligible in the absence of or out of proportion to any dysphasia, or is mute/anarthricUntestable – intubated or other physical barrier (provide explanation)
11. Extinction and inattention (formerly neglect): sufficient information to identify neglect may be obtained during prior testing; if patient has severe visual loss preventing visual double simultaneous stimulation, and cutaneous stimuli are normal, score is normal; if patient has aphasia but does appear to attend to both sides, score is normal; presence of visual spatial neglect or anosognosia may also be taken as evidence of abnormality; since abnormality scored only if present, item is never untestable0 – no abnormality1 – visual, tactile, auditory, spatial, or personal inattention or extinction to bilateral simultaneous stimulation in 1 of the sensory modalities2 – profound hemi-inattention or extinction to > 1 modality; does not recognize own hand or orients to only 1 side of space
12. Bulbar signs (cough and dysphagia assessment): perform with patient upright, alert, and response (NIHSS 1a = 0) and able to follow commands (NIHSS 1c = 0); step 1: ask patient to cough; if patient can cough voluntarily, proceed to step 2: look for anatomical abnormalities such as palatal paralysis/asymmetry or tongue deviation; if no anatomical abnormalities, proceed to step 3: ask patient to swallow their own saliva, if patient can swallow own saliva, perform Gugging Swallowing Screen: ask patient to swallow 5 mL water; if yes, attempt 10 mL water; if yes, attempt 20 mL water; if yes, attempt 50 mL water0 – no dysphagia; performed all 3 steps with no abnormalities4 – inability to perform all parts of step 3 without coughing, clearing throat, or drooling for 1 minute4 – anatomical abnormalities from step 29 – weak or absent voluntary cough from step 1 (5 points for cough and 4 for dysphagia)

Citation: * Administer stroke scale items in the order listed. Record performance in each category after each subscale exam. Do not go back and change scores. Follow directions provided for each exam technique. Scores should reflect what the patient does, not what the clinician thinks the patient can do. The clinician should record answers while administering the exam and work quickly. Except where indicated, the patient should not be coached (for example, do not make repeated requests to patient to make a special effort). Note the time the stroke scale was administered and the interval since stroke onset or last known well, such as, baseline, 2 hours post treatment, 24 hours post onset, 7-10 days post onset, or 3 months post onset. For scoring: add the individual scores for each item. Total score range 0-54 points, with higher scores indicating greater symptom severity.References – Stroke 2022 Apr;53(4):1247 full-text, National Institute of Neurological Disorders and Stroke (NINDS) 2022 Jul 25 PDF.

Modified Rankin Scale

  • modified Rankin Scale (mRS) commonly used to report level of disability in stroke studies
    • total score range 0 (not disabled) to 6 (dead)
    • 0 (not disabled) – no symptoms
    • 1 (no significant disability) – some symptoms but able to carry out all duties
    • 2 (slight disability) – unable to carry out some previous activities but able to look after own affairs without assistance
    • 3 (moderate disability) – requiring some help but able to walk without assistance
    • 4 (moderately severe disability) – unable to walk without assistance and unable to attend to bodily needs without assistance
    • 5 (severe disability) – bedridden, incontinent, and requiring constant nursing care and attention
    • 6 (dead)
    • Reference – Stroke 2017 Jul;48(7):2007full-text

Glasgow Coma Scale (GCS)

  • GCS estimates head injury severity by measuring best eye, motor, and verbal responses
  • total score calculated by summing eye, motor, and verbal response scores
    • range 3 (no responses) to 15 (normal responses)
    • 3-8: severe head injury
    • 9-12: moderate head injury
    • 13-15: mild head injury
  • eye opening
    • spontaneously – 4 points
    • to verbal commands – 3 points
    • to pain – 2 points
    • none – 1 point
  • best motor response
    • follows verbal command – 6 points
    • localizes painful stimuli – 5 points
    • normal flexion to painful stimuli – 4 points
    • abnormal flexion to painful stimuli – 3 points
    • decerebrate posturing to painful stimuli – 2 points
    • none – 1 point
  • best verbal response
    • oriented conversation – 5 points
    • disoriented conversation – 4 points
    • inappropriate or incomprehensible words – 3 points
    • incomprehensible sounds – 2 points
    • none – 1 point
  • Reference – BMJ 2019 May 2;365:l1296
  • GCS Aid documents in English PDF and other languages from Glasgow Coma Scale website

Diagnosis

Making the Diagnosis

  • suspect acute basilar artery occlusion as a possible diagnosis in patients presenting with impaired consciousness, bulbar symptoms, oculomotor dysfunction, other signs of cranial nerve dysfunction, paresis, and/or other motor symptoms
  • determine the precise time of symptom onset (when patient was last asymptomatic and at neurological baseline, or when they were “last known well”) to help inform eligibility for thrombolytic and endovascular therapy
  • urgently obtain brain imaging with noncontrast computed tomography (NCCT) or magnetic resonance imaging (MRI) to evaluate for stroke and rule out intracranial hemorrhage
    • hyperdense basilar artery sign on NCCT may indicate basilar artery occlusion, but NCCT has limited sensitivity
    • also use CT angiography (CTA), which has higher sensitivity than NCCT
    • CT perfusion can help differentiate between potentially salvageable hypoperfused brain tissue (ischemic penumbra) from irreversibly infarcted tissue (ischemic core); however, may be more difficult to interpret for basilar artery occlusion than for anterior circulation stroke
    • MRI has greater sensitivity than NCCT but may have limited availability, and is contraindicated if metallic foreign bodies or older generation implantable devices

Differential Diagnosis

  • other posterior circulation artery strokes
    • common clinical features of posterior circulation strokes include
      • unilateral limb paresis, facial muscle paresis (including speech difficulties), impaired gait, and nystagmus
      • nonspecific symptoms: dizziness, nausea, headache, impaired consciousness, vertigo, and vomiting
    • major posterior circulation arteries include
      • basilar artery
      • vertebral arteries
      • cerebellar arteries
      • posterior cerebral arteries
    • References – Neurol Sci 2019 Oct;40(10):1995, Int J Stroke 2022 Aug;17(7):714
  • other cerebrovascular events(2)
    • ischemic stroke in other areas
    • intracerebral hemorrhage
    • subarachnoid hemorrhage
  • other conditions(2,4)
    • alcohol intoxication
    • basilar migraine
    • Bickerstaff encephalitis
    • brain mass
    • botulism
    • cardiogenic shock
    • central pontine myelinolysis/osmotic demyelination syndrome
    • cranial neuritis
    • drug overdose
    • Guillain Barre syndrome/Miller-Fisher syndrome
    • hemorrhagic shock
    • hypoglycemia
    • hypoxic-ischemic brain injury
    • meningitis or other central nervous system infection
    • metabolic coma
    • myasthenic crisis
    • seizures and postictal state
    • toxic-metabolic encephalopathy

Testing Overview Including Non-Imaging Tests

  • brain imaging
    • noncontrast computed tomography (NCCT) or magnetic resonance imaging (MRI) to evaluate for stroke and rule out intracranial hemorrhage
      • NCCT has limited sensitivity for basilar artery occlusion
      • MRI may have limited availability and may be contraindicated in some patients
    • CT angiography (CTA) has higher sensitivity than NCCT
    • CT perfusion can help differentiate between potentially salvageable hypoperfused brain tissue (ischemic penumbra) from irreversibly infarcted tissue (ischemic core); may be more difficult to interpret for basilar artery occlusion than for anterior circulation stroke
  • non-imaging tests for all patients with suspected stroke include
    • blood glucose, serum electrolytes, and renal function tests
    • electrocardiogram (ECG) and markers of cardiac ischemia
    • complete blood count including platelet count, prothrombin time/INR, and activated partial thromboplastin time
    • oxygen saturation
    • other tests as indicated by the clinical presentation, such as pregnancy test, toxicology screen, blood alcohol level, arterial blood gas, chest radiography, lumbar puncture (to rule out central nervous system infection), and electroencephalography for seizure, postictal state, or encephalopathy for seizure, postictal state, or encephalopathy

Brain Imaging

Noncontrast Computed Tomography (NCCT)

  • urgently image brain with NCCT or magnetic resonance imaging (MRI) to evaluate for stroke and rule out intracranial hemorrhage
    • NCCT is usually the preferred initial neuroimaging modality to quickly distinguish between ischemic and hemorrhagic stroke due to high sensitivity for detecting hemorrhages, wide availability, and speed compared to MRI
    • intracranial hemorrhage is a contraindication for ischemic stroke treatments (thrombolytic and endovascular therapies)
    • ischemic lesions appear dark (hypoattenuated) and there is a loss of gray-white matter differentiation during the acute phase
    • hyperdense artery sign (hyperdensity within an artery) may indicate thrombus in an intracranial artery
    • computed tomography angiography (CTA) or magnetic resonance angiography (MRA) should also be part of the initial imaging evaluations for patients who may be eligible for endovascular therapy for ischemic stroke
    • for additional information on NCCT for stroke in general, see
      • Neuroimaging for Acute Stroke
      • Acute Ischemic Stroke
  • NCCT alone may not be able to detect posterior circulation ischemic lesions including those due to basilar artery occlusion(1,2,3)
    • sensitivity for acute posterior fossa infarction reported to be 42%; may be due to imaging artifacts
    • older patients may have increased risk of false-positives due to increased likelihood of mural calcifications
  • hyperdense basilar artery sign may indicate thrombus within the basilar artery
    • reported sensitivities range from 68% to 94%, with specificities 80%-98%
    • sensitivity higher in patients with high suspicion of basilar artery occlusion by clinical features
    • lack of hyperdense sign cannot exclude basilar artery occlusion
    • Reference – Exp Ther Med 2021 Sep;22(3):954full-text
  • NCCT may help evaluate severity of ischemia, such as when used for pc-ASPECTS or other imaging-based scoring; see Imaging-Based Scoring Systems for details
  • hyperdense basilar artery sign on NCCT may have low sensitivity but moderate specificity for diagnosing basilar artery occlusion (level 2 [mid-level] evidence)
    •  based on 2 diagnostic case-control studies
    • 60 adults (mean age 66 years) with basilar artery occlusion were compared to 65 control patients (mean age 64.4 years) with suspected acute stroke but no occlusion or dissection
      • all patients had NCCT; basilar artery occlusion diagnosed by CTA or digital subtraction angiography (DSA); lack of occlusion in control group determined by CTA
      • hyperdense basilar artery sign on NCCT assessed by 2 attending emergency physicians, 1 resident emergency physician, and 1 medical student
        • each physician had a 30-minute tutorial on qualitative assessment of hyperdense basilar artery sign
        • semiquantitative assessment of hyperdense basilar artery sign determined by optimal cutoff Hounsfield unit (HU) for each physician
      • diagnostic performance of hyperdense basilar artery sign for diagnosing basilar artery occlusion
        • by qualitative assessment by the 3 physicians had
          • sensitivities 54%, 63%, and 63%
          • specificities 89%, 60%, and 55%
        • by semiquantitative assessments by the 3 physicians (with cutoffs 61.8 HU, 61.3 HU, and 63.8 HU) had
          • sensitivities 51%, 52%, and 41%
          • specificities 92%, 85%, and 94%
      • Reference – West J Emerg Med 2020 Apr 13;21(3):694full-text
    • 41 patients with basilar artery occlusion were compared to 41 age-matched controls without basilar artery occlusion
      • all patients had NCCT; basilar artery occlusion diagnosed by CTA
      • basilar artery occlusion on NCCT was identified by 3 independent readers using
        •  visual hyperdensity hyperdense basilar artery (hyperdensity score 4 or 5 out of 5)
        •  basilar artery attenuation in region of interest
      • for detecting basilar artery occlusion, NCCT with cutoff 40-42 Hounsfield units had
        •  sensitivity 61%-78%
        •  specificity 75%-82%
      •  Reference – Neuroradiology 2012 Apr;54(4):321

CT Angiography (CTA) and CT Perfusion (CTP)

  • CTA may help(2)
    • identify basilar artery occlusion (much higher sensitivity than NCCT)
    • differentiate between embolic and atherosclerotic etiology
    • evaluate severity of ischemia to help guide management
  • CTP may help differentiate between potentially salvageable hypoperfused brain tissue (ischemic penumbra) from irreversibly infarcted tissue (ischemic core)(1,3)
    • adds assessment of capillary blood flow to CTA
    • can potentially differentiate ischemic penumbra (salvageable hypoperfused tissue) from ischemic core (unsalvageable infarcted tissue)
      • both penumbra and core have increased mean transit time (MTT) and reduced cerebral blood volume (CBV)
      • core but not penumbra has reduced cerebral blood flow (CBF)
    • fewer areas of hypoperfusion (such as time to reach maximum concentration in seconds [T max] > 10 seconds) on CTP may be associated with better outcomes following endovascular therapy in patients with basilar artery occlusion
    • however, may be more difficult to interpret for basilar artery occlusion than for anterior circulation stroke
      • most evidence evaluating clinical utility of CTP involves anterior circulation stroke
      • there is a lack of widely accepted validated thresholds for defining penumbra and ischemic core
  • CTA and CTP may help evaluate severity of ischemia, such as when used for pc-ASPECTS, BATMAN, CAPS, or other imaging-based scoring; see Imaging-Based Scoring Systems for details

Magnetic Resonance Imaging (MRI)

  • use MRI or NCCT to evaluate for stroke and rule out intracranial hemorrhage
    • NCCT is usually preferred over MRI as initial neuroimaging modality to quickly evaluate acute stroke due to higher sensitivity for detecting hemorrhages, wider availability and greater speed, and relatively fewer contraindications (MRI cannot be performed in patients with metallic foreign bodies or older generation implantable devices)
    • ischemic lesion signs on MRI include
      • absent arterial flow void on T2, which may suggest slow flow or occlusion
      • hyperintense (bright) signal on diffusion-weighted imaging (DWI)
      • hypointense artery (“blooming”) on gradient recalled echo (GRE), suggesting thrombus in artery
      • intravascular hyperintensity on fluid-attenuated inversion recovery (FLAIR), suggesting slow or collateral flow
    • noninvasive magnetic resonance angiography (MRA) or CTA should also be part of the initial imaging evaluations for patient who may be eligible for endovascular therapy for ischemic stroke
    • DWI helps to further characterize ischemic stroke to guide additional investigations and management, particularly to determine eligibility for thrombolytic and endovascular therapy
    • for additional information on MRI for stroke in general, see Neuroimaging for Acute Stroke
  • MRI findings for basilar artery occlusion similar to ischemic stroke in general
    • on T2 and FLAIR
      • ischemic areas may appear hyperintense on T2 and FLAIR; hyperintense areas may also help predict final infarction(3)
      • note that T2 and FLAIR sequences may not demonstrate hyperintensity for several hours after stroke onset (Radiol Clin North Am 2019 Jul;57(4):717)
    • DWI(2,3)
      • higher sensitivity than CT modalities for detecting hyperacute posterior cerebral circulation ischemia
      • hyperacute ischemic lesions appear as hyperintense areas associated with low apparent diffusion coefficient (ADC) values
      • global volume of lesion on DWI may not be consistent with severity of symptoms or help predict functional outcome
    • areas of discrepancies between DWI and FLAIR (“mismatch”) may be indicative of ischemia but not irreversibly infarcted tissue(2)
    • occlusion may appear as missing segment on MRA(4)
  • lower pretherapy posterior circulation lesion volume on DWI associated with greater 90-day functional independence following endovascular therapy for basilar artery occlusion
    • based on retrospective cohort study
    • 110 adults (mean age 67 years, 60% male) with basilar artery occlusion from 2011 to 2018 who had MRI including DWI before endovascular therapy were assessed
    • patients excluded if brain stem ischemic lesion on DWI involving > 80% of area in axial view
    • posterior circulation lesion volume (PCLV) defined as infarct on DWI in ≥ 1 of brain stem, cerebellar structures, thalamosubthalamic area, and occipitotemporal lobes
    • lower PCLV associated with greater likelihood of functional independence (modified Rankin Scale [mRS] 0-2) at 90 days
      • 32% had functional independence
      • median PCLV
        • 2.1 mL for patients with functional independence (p = 0.024 in adjusted analysis)
        • 7.9 mL for patients without functional independence
      • for predicting 90-day functional independence, PCLV ≤ 8.7 mL had
        • sensitivity 89%
        • specificity 49%
    • lower PCLV associated with greater likelihood of survival at 90 days
      • 41% died within 90 days (median 6 days)
      • median PCLV
        • 2.7 mL for patients who survived (p = 0.003 in adjusted analysis)
        • 10.6 mL for patients who died
      • for predicting 90-day mortality, PCLV ≥ 9.1 mL had
        • sensitivity 80%
        • specificity 60%
    • Reference – Neuroradiology 2022 Jun;64(6):1231

Other Imaging Studies

  • digital subtraction angiography (DSA) is reference standard for diagnosing basilar artery occlusion but is invasive and not usually used as the initial imaging modality(3)
    • contrast filling defect within the basilar artery by DSA indicates basilar artery occlusion
    • can evaluate both intracranial and extracranial vertebrobasilar vessels
    • can confirm diagnosis (if needed) when performing endovascular arterial recanalization, and evaluate reperfusion following treatment
  • transcranial ultrasound can be considered if other imaging modalities not possible, but has limited sensitivity and is operator-dependent (Neurol Sci 2019 Oct;40(10):2007)

Imaging-Based Scoring Systems

Posterior Circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS)

  • description of pc-ASPECTS
    • total score range 0-10 points
      • lower scores indicate more posterior circulation areas with ischemic damage
      • score ≥ 8 points associated with better prognosis
    • starting with 10 points, subtract points for ischemic changes (noncontrast computed tomography [NCCT]) or hypoattenuation (computed tomography angiography [CTA]) in posterior circulation areas:
      • midbrain (-2 points)
      • pons (-2 points)
      • thalamus (-1 point each for left and right)
      • cerebellum (-1 point each for left and right)
      • posterior cerebral artery territory (-1 point each for left and right)
    • References – Stroke 2008 Sep;39(9):2485, Exp Ther Med 2021 Sep;22(3):954
  • adults with basilar artery occlusion who have pc-ASPECTS score ≥ 5 points on NCCT may benefit from endovascular therapy
    • based on retrospective cohort study
    • 823 adults (median age 65 years, 26% female) with basilar artery occlusion were evaluated within 24 hours of symptom onset using pc-ASPECTS by NCCT
      • pc-ASPECTS score quantifies extent of ischemia in posterior circulation; total score range 0 (high ischemic burden) to 10 (no ischemia)
      • patient data from BASILAR study (JAMA Neurol 2020), a nonrandomized study conducted in multiple stroke centers in China from 2014 to 2019
    • endovascular therapy performed in 654 patients (79%), including
      • 25 (66%) of 38 patients with pc-ASPECTS 0-4 points
      • 232 (73%) of 317 patients with pc-ASPECTS 5-7 points
      • 397 (85%) of 468 patients with pc-ASPECTS 8-10 points
    • effect of endovascular therapy on outcomes quantified as risk ratio (RR) or odds ratio (OR) of outcome adjusted for age, sex, history of diabetes or ischemic stroke, baseline NIHSS, onset to imaging time, and location of occlusion
    • comparing endovascular therapy vs. standard medical therapy alone at 90 days
      • in 38 patients with pc-ASPECTS 0-4 points
        • favorable outcome (modified Rankin Scale [mRS] 0-3 points) in 4% vs. 0% (not significant)
        • death in 80% vs. 84.6% (not significant)
      • in 317 patients with pc-ASPECTS 5-7 points
        • favorable outcome (mRS 0-3 points) in 15.5% vs. 3.5% (adjusted RR 4.35, 95% CI 1.3-14.48)
        • death in 60.8% vs. 77.6% (adjusted OR 0.36, 95% CI 0.19-0.68)
      • in 468 patients with pc-ASPECTS 8-10 points
        • favorable outcome (mRS 0-3 points) in 43.8% vs. 14.1% (adjusted RR 3.2, 95% CI 1.68-6.09)
        • death in 35% vs. 66.2% (adjusted OR 0.19, 95% CI 0.1-0.36)
    • Reference – Stroke 2021 Mar;52(3):811

Basilar Artery on Computed Tomography Angiography (BATMAN) Score

  • description of BATMAN score
    • based on occlusions in vertebrobasilar system and patency of primary collaterals
    • total score range 0-10 points
      • lower scores indicate more occlusions and less patency of collaterals
      • score < 7 points associated with poor outcomes
    • add points for each patent segment
      • either vertebral artery (+1 point)
      • proximal basilar artery (+1 point)
      • middle basilar artery (+1 point)
      • distal basilar artery (+1 point)
      • P1 posterior cerebral artery (+1 point each for left and right)
      • posterior communicating arteries > 1 mm diameter (+2 points each for left and right)
      • posterior communicating arteries ≤ 1 mm diameter (+1 point each for left and right)
      • fetal posterior communicating arteries (with absent P1 segments) (+3 point each for left and right)
    • References – Stroke 2017 Mar;48(3):631, Exp Ther Med 2021 Sep;22(3):954
  • patients with any occlusion severity by BATMAN score may benefit from endovascular therapy
    • based on retrospective cohort study
    • 828 adults with acute ischemic stroke and basilar artery occlusion who had acute treatment according to eligibility ≤ 24 hours after onset were evaluated
    • patient data from BASILAR study (JAMA Neurol 2020), a cohort study using data from patients treated for basilar artery occlusion from 2014-2019 in China
    • functional independence defined as mRS 0-2 points at 90 days
    • comparing outcomes with mechanical thrombectomy vs. standard medical care alone
      • among 337 patients with BATMAN score 0-3 points (severe occlusions)
        • mRS 0-2 at 90 days in 39.4% vs. 9.6% (p = 0.003)
        • mortality at 90 days 57.2% vs. 89.4% (p < 0.001)
        • symptomatic intracranial hemorrhage in 7.9% vs. 0% (p = 0.011)
      • among 386 patients with BATMAN score 4-6 points (moderate occlusions)
        • mRS 0-2 at 90 days in 32.5% vs. 11.5% (p < 0.001)
        • mortality at 90 days 39.9% vs. 67.9% (p < 0.001)
        • symptomatic intracranial hemorrhage in 7.9% vs. 1.3% (p = 0.034)
      • among 105 patients with BATMAN score 7-10 points (mild occlusions)
        • mRS 0-2 at 90 days in 43.3% vs. 5.3% (p < 0.001)
        • mortality at 90 days in 31.3% vs. 47.4% (not significant)
        • symptomatic intracranial hemorrhage in 0% of both groups
    • mechanical thrombectomy in multivariable analyses
      • associated with increased likelihood of mRS 0-2 at 90 days for patients with mild, moderate, and severe occlusions by BATMAN
      • associated with reduced mortality at 90 days for patients with mild and moderate, but not severe occlusions by BATMAN
      • not associated with altered risk of symptomatic intracranial hemorrhage for any occlusion severity
    • Reference – J Neurol 2022 Jul;269(7):3810

Critical Area Perfusion Score (CAPS)

  • description of CAPS
    • total score range 0-6 points
      • higher scores indicate more occlusion (areas of low perfusion)
      • score > 3 points associated with poor outcomes
    • area of low perfusion defined by presence of time to reach maximum concentration in seconds (T max) > 10 seconds in adjacent axial image slices in which ≥ 1 slice has an area with diameter ≥ 6 mm
    • add points for brain regions with areas of low perfusion
      • cerebellum (+1 point for each hemisphere)
      • pons (+2 points)
      • midbrain and/or thalamus (+2 points)
    • References – Ann Neurol 2022 Jan;91(1):23, Interv Neuroradiol 2022 Sep 13;:15910199221125853
  • baseline CAPS score ≤ 3 points associated with increased likelihood of 90-day favorable outcomes among adults having endovascular therapy for basilar artery occlusion
    • based on 2 retrospective cohort studies, both of which
      • evaluated prognostic performance of CAPS (total score range 0-6 points, with higher scores indicating more areas of low perfusion)
      • assessed for favorable outcome (mRS 0-3 points) at 90 days
    • 103 adults (mean age 65 years, 65% male) with basilar artery occlusion who had CT or magnetic resonance (MR) perfusion before endovascular therapy during 2015-2019 were assessed
      • 87% had CT perfusion (CTP), 12% had MR perfusion (MRP), and 1% had both
      • baseline imaging-based scores
        • median CAPS 0 points; 87% had CAPS score ≤ 3 points
        • median pc-ASPECTS score 9 points (total score range 0-10 points, with lower scores indicating more posterior circulation areas with ischemic damage); imaged with NCCT or diffusion-weighted imaging (DWI) magnetic resonance imaging (MRI), and CTA if NCCT not obtained
        • same neuroradiologist participated in calculating both CAPS and pc-ASPECTS scores
      • at 90 days, 50 patients (49%) had favorable outcome (mRS 0-3 points); 62 patients (60%) were alive
      • factors associated with increased likelihood of favorable outcome at 90 days in multivariable analysis
        • CAPS ≤ 3 points (adjusted odds ratio [OR] 39.25, 95% CI 1.34-999)
        • successful reperfusion (modified Thrombolysis in Cerebral Infarction [mTICI] 2b-3) (adjusted OR 22.1, 95% CI 2.93-182)
        • lower age (adjusted OR per 5-year increase 0.71, 95% CI 0.56-0.89)
        • lower clinical severity (adjusted OR per 1-point increase in National Institutes of Health Stroke Scale (NIHSS) 0.89, 95% CI 0.83-0.95)
      • increased pc-ASPECTS score associated with nonsignificant increased likelihood of favorable outcome in multivariable analysis
        • adjusted OR per 1-point increase 1.4 (95% CI 0.985-1.98)
        • risk with dichotomized pc-ASPECTS score (such as score ≥ 8 points) not reported
      • Reference – Ann Neurol 2022 Jan;91(1):23
    • 65 adults (median age 64 years, 85% male) with basilar artery occlusion who had CTP before endovascular therapy during 2020-2021 were assessed
      • baseline imaging-based scores
        • median CAPS 3 points
        • median pc-ASPECTS 8 points (by NCCT) and 7 points (by CTA)
      • at 90 days, 29 patients (44.6%) had favorable outcome (mRS 0-3 points)
      • factors associated with increased likelihood of favorable outcome at 90 days in multivariable analysis
        • lower clinical severity (adjusted OR per 1-point increase in NIHSS 0.8, 95% CI 0.7-0.91)
        • fewer areas of low perfusion (adjusted OR per 1-point increase in CAPS 0.43, 95% CI 0.22-0.86)
      • for predicting likelihood of favorable outcome at 90 days, CAPS ≤ 3 points had
        • sensitivity 89.66%
        • specificity 72.22%
      • Reference – Interv Neuroradiol 2022 Sep 13;:15910199221125853

Other Imaging-Based Scoring Systems

  • Posterior Circulation CT Angiography (pc-CTA) score – total score range 0-6 points, with higher scores indicating more occlusions(1)
  • Posterior Circulation Collateral Score (PC-CS) – total score range 0-10 points, with higher scores indicating fewer occlusions(1)
  • Pretreatment Collateral Score (CS) – total score range 0-2 points, with score of 2 indicating that both posterior communicating arteries are patent(1)
  • Renard DWI Score – total score range 0-10 points, with higher scores indicating more brain areas involved(1)
  • Brain stem DWI (BS DWI) – total score range 0-22 points, with higher scores indicating more brain areas involved(1)

Management

Management Overview

  • supportive management for acute ischemic stroke in general includes
    • airway support and supplemental oxygen if needed
    • manage reduced or elevated blood pressure
    • maintain balanced blood glucose levels
  • start IV thrombolytics in eligible patients presenting ≤ 3-4.5 hours after stroke onset
    • IV alteplase is commonly used, but IV tenecteplase can also be considered
      • alteplase dose: 0.9 mg/kg (maximum dose 90 mg) IV with first 10% of total dose given as IV bolus over 1 minute and remaining 90% of dose given as IV infusion over 1 hour
      • tenecteplase dose: 0.25 mg/kg (maximum 25 mg) IV single bolus over 5 seconds
  • refer for emergent endovascular therapy in eligible patients presenting ≤ 24 hours after stroke onset
    • mechanical thrombectomy with stent retriever or direct aspiration preferred
    • evidence has demonstrated that endovascular therapy (particularly mechanical thrombectomy) within 24 hours of acute ischemic stroke with basilar artery occlusion improves functional outcomes
    • may be particularly beneficial in patients with severe clinical severity and small infarction on imaging
  • antiplatelet therapy for acute ischemic stroke in general
    • start aspirin therapy 160-300 mg/day orally within 24-48 hours of stroke onset
    • delay aspirin therapy for 24 hours in patients who had thrombolytic therapy, but consider starting earlier if comorbid conditions for which aspirin may be beneficial
    • start dual antiplatelet therapy if noncardioembolic ischemic stroke and no thrombolytic therapy
    • for a detailed discussion, see Antithrombotic Therapy for Secondary Prevention of Stroke or TIA

Supportive Management

  • urgent supportive management for acute ischemic stroke in general includes
    • airway support and supplemental oxygen if needed
    • managing reduced or elevated blood pressure
    • maintaining balanced blood glucose levels

IV Thrombolytics

  • IV thrombolytics is standard of care for acute ischemic stroke in general(2)
    • IV thrombolytics preferred over intra-arterial thrombolytics due to relative ease of administration and strong evidence base for ischemic stroke in general
    • evidence specifically for basilar artery occlusion is limited
  • overview of IV thrombolytics for acute stroke in general
    • start IV thrombolytics in eligible patients with acute ischemic stroke with onset ≤ 3-4.5 hours previous
    • IV alteplase is commonly used and is FDA approved for acute ischemic stroke, but IV tenecteplase can also be considered
      • alteplase dose: 0.9 mg/kg (maximum dose 90 mg) IV with first 10% of total dose given as IV bolus over 1 minute and remaining 90% of dose given as IV infusion over 1 hour
      • tenecteplase dose: 0.25 mg/kg (maximum 25 mg) IV single bolus over 5 seconds
    • contraindications include intracranial or subarachnoid hemorrhage, active internal bleeding, recent (within 3 months) intracranial or intraspinal surgery or serious head trauma, increased risk of bleeding due to intracranial conditions, and current uncontrolled hypertension despite antihypertensive therapy
  • IV thrombolytics before mechanical thrombectomy might not alter likelihood of functional independence at 90 days compared to mechanical thrombectomy alone in patients with acute ischemic stroke with basilar artery occlusion (level 2 [mid-level] evidence)
    • based on retrospective cohort study
    • 322 patients (mean age 67 years, 64% male, 65% White) with acute ischemic stroke with basilar artery occlusion who had mechanical thrombectomy during 2015-2019 were assessed via patient records
      • 127 patients (39%) had IV thrombolytics before thrombectomy (if eligible, presenting within 4.5 hours of stroke onset, and at physician’s discretion)
      • 195 patients (61%) did not have IV thrombolytics
      • mean National Institutes of Health Stroke Scale (NIHSS) 16 points
      • underlying etiologies were cardioembolic (43%), large-artery atherosclerosis (31%), undetermined (22%), other identified etiology (4%)
    • comparing patients with vs. without IV thrombolytics before thrombectomy
      • median time from stroke onset to groin puncture 240 vs. 330 minutes (no p value reported)
      • functional independence (modified Rankin Scale [mRS] 0-2 points) at 90 days in 30% vs. 27% (not significant)
      • in-hospital mortality 20% vs. 27% (not significant)
      • symptomatic intracranial hemorrhage at 24 hours in 5% vs. 4.4% (not significant)
      • in 101 patients with large-artery atherosclerosis
        • functional independence (mRS 0-2 points) at 90 days in 28% vs. 8.6% (p = 0.01)
        • in-hospital mortality 16% vs. 36% (p = 0.027)
        • symptomatic intracranial hemorrhage at 24 hours in 7% vs. 6.9% (not significant)
    • Reference – J Stroke 2022 Jan;24(1):128full-text

Endovascular Therapy

Overview

  • endovascular therapy (particularly mechanical thrombectomy) within 24 hours of acute ischemic stroke with basilar artery (BA) occlusion improves functional outcomes; see evidence summaries for details
  • professional organizations recommend considering endovascular therapy (EVT) in addition to IV thrombolytics for BA occlusion based on expected risks and benefits
    • potential eligibility includes
      • last known well ≤ 6 hours previous
      • last known well ≤ 24 hours previous and imaging evidence of salvageable brain tissue
  • techniques include(1)
    • mechanical thrombectomy with stent retriever
    • mechanical thrombectomy with first-line direct aspiration (may be more beneficial than stent retriever, especially if embolic BA occlusion, but evidence limited)
    • angioplasty may also be considered, especially if intracranial atherosclerotic disease (ICAD) or for residual stenosis related to ICAD
  • factors that may be associated with greater benefit of mechanical thrombectomy include(1)
    • severe clinical severity (such as National Institutes of Health Stroke Scale [NIHSS] > 10 points)
    • small infarction on imaging, particularly if smaller than expected for the clinical severity
    • age < 75 years
    • reduced consciousness
    • tetraplegia/tetraparesis
    • locked-in syndrome
    • BA occlusion secondary to embolism (compared to BA secondary to ICAD)
    • distal basilar tip occlusion (compared to proximal occlusion)
  • factors that may be associated with lesser benefit of mechanical thrombectomy include(1)
    • perforator occlusion from branch atheromatous disease
    • posterior stroke not involving BA (isolated posterior cerebral or vertebral artery occlusion)
    • large brain stem infarction
  • technical considerations(1)
    • transfemoral access commonly used
    • transradial access has become more common and may be preferred for reaching basilar artery, particularly if
      • vessel tortuosity
      • aortic arch developmental variants
      • marked calcification of abdominal aorta and descending thoracic aorta
    • transradial access also allows more direct access to vertebral artery, but small diameter (about 3 mm) may limit catheter and device choices
    • use of intracranial stents may be considered
      • has been used for persistent stenosis secondary to intracranial atherosclerotic disease refractory to medical management
      • however, evidence limited

Evidence

  • EVIDENCE SYNOPSIS: Endovascular therapy (including mechanical thrombectomy) in addition to standard care improves 90-day functional outcomes in adults with acute ischemic stroke with basilar artery occlusion, as demonstrated in a 2023 systematic review, which includes the high-quality ATTENTION (2022) and BAOCHE (2022) trials. There was also reduced overall mortality and an increased risk of symptomatic intracranial hemorrhage.
    • endovascular thrombectomy in addition to standard care improves 90-day functional outcomes in adults with acute ischemic stroke with basilar artery occlusion (level 1 [likely reliable] evidence)
      • based on systematic review with consistent result in high-quality trials
      • systematic review of 4 randomized trials evaluating endovascular thrombectomy in addition to standard care in 988 adults with acute ischemic stroke with basilar artery occlusion
      • included trials were
        • high-quality ATTENTION and BAOCHE trials
        • BEST and BASICS trials, which had poor recruitment and high cross-over rates
      • meta-analyses included all 4 trials
      • endovascular thrombectomy in addition to standard care associated with
        • increased likelihood of good functional status (modified Rankin Scale [mRS] 0-3 points) at 90 days
          • odds ratio (OR) 1.99 (95% CI 1.04-3.8), significant but CI includes differences that may not be clinically important
          • NNT 4-121 with functional independence in 30% of standard care alone group
          • consistent results in high-quality ATTENTION and BAOCHE trials
        • reduced mortality at 90 days
          • OR 0.64 (95% CI 0.42-0.99)
          • NNT 6-403 with mortality 45% of standard care along group
        • increased risk of symptomatic intracranial hemorrhage
          • OR 7.89 (95% CI 4.1-15.19)
          • NNH 15-65 with symptomatic intracranial hemorrhage in 0.5% of standard care alone group
      • Reference – J Stroke 2023 Jan;25(1):81full-text
      • consistent results in other systematic review of the same 4 trials (J Neurointerv Surg 2023 Dec 21;15(e3):e446)
    • endovascular thrombectomy within 12 hours of stroke onset in addition to standard care improves 90-day functional outcomes in adults with acute ischemic stroke with basilar artery occlusion (level 1 [likely reliable] evidence); symptomatic intracranial hemorrhage at 24-72 hours reported in 5% with endovascular thrombectomy
      • based on randomized trial
      • 342 adults (mean age 66 years, 68% male) in China with moderate-to-severe acute ischemic stroke (NIHSS ≥ 10) with BA occlusion were randomized within 12 hours of stroke onset to endovascular thrombectomy plus standard care vs. standard care alone
        • endovascular thrombectomy strategies were at physician’s discretion and included stent retrievers, thromboaspiration, balloon angioplasty, stent deployment, and/or intra-arterial thrombolysis; proportion of patients receiving each type not reported
        • standard care was based on national and institutional guidelines and included IV thrombolytic agents, antiplatelet drugs, and/or anticoagulation
        • key exclusion criteria included prestroke mRS ≥ 3 points in patients < 80 years old or mRS ≥ 1 point in patients ≥ 80 years old, and intracranial hemorrhage on neuroimaging
        • median NIHSS 24 points
        • 53.5% had imaging ≤ 4.5 hours after estimated stroke onset
        • IV thrombolytics in 32%
        • occlusion in distal BA in 33.6%, middle BA in 26.8%, proximal BA in 31.9%, and V4 (vertebral artery) in 7.7%
      • primary outcome was good functional status (mRS 0-3 points) at 90 days
      • outcome assessors were blinded
      • comparing endovascular thrombectomy plus standard care vs. standard care alone
        • good functional status (mRS 0-3 points) at 90 days in 46% vs. 23% (p < 0.001, NNT 5)
        • excellent functional status (mRS 0-2 points) at 90 days in 33% vs. 11% (p < 0.05, NNT 5)
        • median NIHSS score at 5-7 days or at discharge 16 points vs. 35 points (p < 0.05)
        • symptomatic intracranial hemorrhage at 24-72 hours in 5% vs. 0% (no p value reported)
        • 90-day mortality 37% vs. 55% (p < 0.05, NNT 6)
      • no significant difference in good functional status at 90 days in subgroup of 37 patients ≥ 80 years old
      • procedural complications occurred in 14% in thrombectomy group, including 1 death due to arterial perforation
      • Reference – ATTENTION trial (N Engl J Med 2022 Oct 13;387(15):1361), editorial can be found in N Engl J Med 2022 Oct 13;387(15):1428
    • mechanical thrombectomy with stent retriever within 6-24 hours of stroke onset in addition to standard care improves 90-day functional outcomes in adults with acute ischemic stroke with basilar artery occlusion (level 1 [likely reliable] evidence); symptomatic intracranial hemorrhage at 24 hours in reported in 6% with mechanical thrombectomy
      •  based on randomized trial
      • 218 adults ≤ 80 years old (mean age 64 years, 73% male) in China with acute ischemic stroke with BA occlusion were randomized within 6-24 hours of symptom onset to mechanical thrombectomy with stent retriever (Solitaire device) plus standard care vs. standard care alone
        • standard care was based on guidelines in China for acute ischemic stroke management and could include IV thrombolysis
        • key exclusion criteria included recent intracranial hemorrhage and large infarct in posterior circulation or in brain stem on imaging
        • median NIHSS 20 points
        • median time after symptom onset was 11 hours
        • IV thrombolytics in 18%
        • occlusion in distal BA in 17%, middle BA in 36%, and proximal BA in 46%
      • outcome assessors were blinded
      • trial was terminated early after prespecified interim analysis showed superiority of thrombectomy; planned enrollment was 318 patients
      • primary outcome was good functional status (mRS 0-3 points) at 90 days
      • comparing thrombectomy plus standard care vs. standard care alone
        • mRS score 0-3 points at 90 days in 46% vs. 24% (p < 0.001, NNT 5)
        • mRS score 0-2 points at 90 days in 39% vs. 14% (p < 0.05, NNT 4)
        • neurologic improvement (NIHSS reduction of ≥ 8 points or NIHSS 0-2) at 24 hours in 25% vs. 10% (p < 0.05, NNT 7)
        • symptomatic intracranial hemorrhage at 24 hours in 6% vs. 1% (no p value reported)
        • 90-day mortality 31% vs. 42% (adjusted risk ratio 0.75, 95% CI 0.54-1.04), not significant but CI includes possibility of benefit
      • procedural complications occurred in 11% in thrombectomy group and included vessel dissection (4%), vessel perforation (3%), and distal embolization (5%)
      • Reference – BAOCHE trial (N Engl J Med 2022 Oct 13;387(15):1373), editorial can be found in N Engl J Med 2022 Oct 13;387(15):1428
  • endovascular therapy may moderately increase likelihood of routine discharge to home without services in adults with moderate-to-severe acute basilar artery occlusion (level 2 [mid-level] evidence)
    • based on retrospective cohort study
    • 3,950 adults (mean age 68 years, 59% male) in the United States with moderate-to-severe acute basilar artery occlusion (NIHSS ≥ 10 points) from 2015 to 2019 were assessed
      • patient data from National Inpatient Sample (NIS)
      • racial or ethnic demographics: 64% White, 19% Black, 7% Hispanic, and 5% Asian/Pacific Islander
      • comorbid conditions included hypertension (in 83%), diabetes mellitus (35%), atrial fibrillation (32%), and intracranial atherosclerotic disease (9%)
      • median NIHSS score 22 points; 53% had NIHSS > 20 points
      • 30% had IV thrombolytics
    • 36% had EVT
    • outcomes
      • 8.7% had favorable functional outcome (routine discharge to home without services)
      • 36.5% died in-hospital
      • 1.4% had symptomatic intracranial hemorrhage
    • association between EVT and outcomes estimated with propensity score-adjusted analysis
      • propensity scores based on disease severity, comorbidities, age, NIHSS score, presence of severe feature, and use of IV thrombolytics
      • adjustment by inverse probability of treatment weighting and then as covariate in multivariable logistic regression analysis
    • EVT
      • associated with increased likelihood of favorable functional outcome (adjusted odds ratio 1.25, 95% CI 1.07-1.46)
      • not associated with altered risks of in-hospital death or symptomatic intracranial hemorrhage
    • Reference – BArONIS trial (Ann Neurol 2023 Jul;94(1):55)
  • mechanical thrombectomy with direct aspiration and mechanical thrombectomy with stent retriever might have similar likelihoods of 90-day functional independence in patients with acute ischemic stroke with basilar artery occlusion (level 2 [mid-level] evidence)
    • based on systematic review of cohort studies
    • systematic review of 5 cohort studies evaluating mechanical thrombectomy with direct aspiration vs. stent retriever in 476 patients with acute ischemic stroke with basilar artery occlusion
    • direct aspiration compared to stent retriever
      • not associated with altered
        • likelihood of functional independence (mRS 0-2 points) at 90 days in analysis of 4 studies (not significant in any study)
        • mortality in analysis of 3 studies (not significant in any study)
      • associated with
        • reduced risk of new territory embolic event (odds ratio [OR] 0.2, 95% CI 0.05-0.83) in analysis of 2 studies
        • increased likelihood of successful recanalization (OR 2, 95% CI 1.13-3.54) in analysis of 5 studies
    • Reference – J Neurointerv Surg 2019 Aug;11(8):740

Antiplatelet Therapy

  • antiplatelet therapy for acute ischemic stroke in general includes
    • starting aspirin therapy 160-300 mg/day orally within 24-48 hours of stroke onset
    • delaying aspirin therapy for 24 hours in patients who had thrombolytic therapy, but consider starting earlier if comorbid conditions for which aspirin may be beneficial
    • starting dual antiplatelet therapy if noncardioembolic ischemic stroke and no thrombolytic therapy
  • anticoagulation therapy generally not recommended for acute stroke management
  • for a detailed discussion, see Antithrombotic Therapy for Secondary Prevention of Stroke or TIA

Complications

Locked-In Syndrome

  • locked-in syndrome characterized by quadriplegia, anarthria (inability to speak), and preserved consciousness
    • usually caused by injury to ventral pons but may also occur with extensive bilateral destruction of corticobulbar and corticospinal tracts in cerebral peduncles
      • most common causes
        • hypoxia, pontine infarction (often due to basilar occlusion), or pontine hemorrhage
        • traumatic injury
      • other causes
        • tumor of ventral pons
        • central pontine myelinolysis
        • multiple sclerosis affecting ventral pons
        • abscess or encephalitis affecting brain stem
    • vertical eye movements and upper lid movement frequently retained due to sparing of midbrain tectum and may facilitate nonverbal communication
    • horizontal eye movements are often impaired
    • classifications
      • classic (loss of motor ability but with vertical eye movements)
      • incomplete (some voluntary motor movement, such as finger, in addition to vertical eye movements)
      • total (no motor ability and no vertical eye movements)
    • diagnosis is clinical, often not suspected until later in admission clinical course, and often prompted by family alerting clinical team to presence of awareness
    • fluorodeoxyglucose-positron emission tomography (FDG-PET) shows only mildly reduced cerebral metabolism, compared to unresponsive wakefulness which shows severe reduction in cerebral metabolism
    • electroencephalogram (EEG) may be normal
    • additional complications may include
      • attention (may be limited initially)
      • visual disturbance (blurring, double vision, and incomplete accommodation)
      • vertigo
      • insomnia
      • emotional lability
      • pulmonary complications (leading cause of death)
        • aspiration
        • atelectasis
        • pneumonia
        • pulmonary embolism
    • management is supportive
      • maintain airway and oxygenation
      • manage reversible medical cause
      • monitor for pulmonary complications
      • chest physiotherapy
      • avoid corneal ulceration due to impaired eye closure; consider lateral tarsorrhaphy or botulinum toxin for incomplete eye closure
      • treat pathological crying with selective serotonin reuptake inhibitors (SSRIs) or dextromethorphan/quinidine
      • engage speech therapy staff to assist with optimal communication methods, using
        • specific rules for communication using eye movements
        • augmentative communication devices, when possible
    • 10-year survival up to 80% reported
    • References – BMJ 2005 Feb 19;330(7488):406full-text, Arch Phys Med Rehabil 1987 Jan;68(1):24, Ibrain 2022 Nov 7;8(4):476, Stroke 2016 Jun;47(6):e98

Top of the Basilar Syndrome

  • characterized by sudden loss of consciousness (due to bilateral thalamic injury)(2)
    • vision loss and cortical blindness is also common (due to bilateral occipital lobe injury)
    • motor function may be unimpaired
    • due to basilar artery occlusion at distal basilar artery

Other Complications

  •  swelling and compression of brain stem (Neurocrit Care 2004;1(3):319)
  • common complications following ischemic stroke in general include
    • persistent neurologic dysfunction
    • secondary brain injury due to cerebral edema
    • swallowing dysfunction
    • pneumonia
    • urinary tract infections
    • deep vein thrombosis
    • pulmonary embolism
    • myocardial ischemia
    • heart failure
    • cardiac arrhythmias
    • seizures
    • fever
    • delirium

Prognosis

  • basilar artery occlusion has higher morbidity and mortality than ischemic strokes with occlusions in other vessels(1,2)
    • 37%-83% reported rates of death or severe disability (modified Rankin Scale [mRS] 4-6)
    • note that high reported rates may be due in part to
      • delayed diagnosis due to unfamiliarity of associated symptoms
      • lack of advanced imaging and imaging-based scoring
      • lack of modern endovascular therapies when rates were reported
  • factors associated with worse prognosis include(1,2)
    • embolic etiology
    • worse clinical severity
    • older age
    • absence of hyperlipidemia
    • prodromal minor stroke
    • longer time to treatment
    • proximal basilar occlusion location
    • prior posterior circulation stroke

Prevention and Screening

Prevention

Screening

  • not applicable

Guidelines and Resources

Guidelines

United States Guidelines

United Kingdom Guidelines

  • National Institute for Health and Care Excellence (NICE) guideline on the diagnosis and initial management of acute stroke and transient ischemic attack (TIA) in over 16s can be found at NICE 2019 May 1:NG128, last updated 2022 Apr 13PDF.
  •  Royal College of Physicians (RCP) national clinical guideline on stroke can be found at RCP 2023 PDF.

Canadian Guidelines

  • Canadian Stroke Best Practice Recommendations (CSBPR):
    • CSBPR landing page for their recommendations can be found at CSBPR 2023.
    • CSBPR recommendations on acute stroke management can be found at CSBPR 2022 .
    • CSBPR recommendations on management of spontaneous intracerebral hemorrhage can be found at CSBPR 2020.
    • CSBPR best practices during COVID-19 pandemic can be found at CSBPR 2020.
    • CSBPR recommendations on telestroke can be found at CSBPR 2017.
    • CSBPR recommendations on pediatric stroke can be found at CSBPR 2015.
    • CSBPR pregnancy-related recommendations for:
      • Acute stroke management during pregnancy can be found at CSBPR 2018.
      • Prevention of recurrent stroke in pregnancy can be found at CSBPR 2016-2018.
    • Poststroke management:
      • CSBPR recommendations on secondary prevention of stroke can be found at CSBPR 2020.
      • CSBPR recommendations on mood, cognition, and fatigue following stroke can be found at CSBPR 2019.
      • CSBPR recommendations on rehabilitation and recovery after stroke can be found at CSBPR 2019.
      • CSBPR recommendations on transitions and community participation following stroke can be found at CSBPR 2019.
    • CSBPR recommendations on acetylsalicylic acid (ASA) for prevention of vascular events can be found at CSBPR 2020.
  • Hypertension Canada comprehensive guideline on prevention, diagnosis, risk assessment, and treatment of hypertension in adults and children can be found in Can J Cardiol 2020 May;36(5):596

European Guidelines

Australian and New Zealand Guidelines

Review Articles

  •  to search MEDLINE for (Basilar Artery Occlusion) with targeted search (Clinical Queries), click therapy, diagnosis, or prognosis

Patient Information

References

General References Used

The references listed below are used in this DynaMed topic primarily to support background information and for guidance where evidence summaries are not felt to be necessary. Most references are incorporated within the text along with the evidence summaries.

  1. Ahmed RA, Dmytriw AA, Patel AB, et al. Basilar artery occlusion: A review of clinicoradiologic features, treatment selection, and endovascular techniques. Interv Neuroradiol. 2022 Jun 12;:15910199221106049.
  2. Buchman SL, Merkler AE. Basilar Artery Occlusion: Diagnosis and Acute Treatment. Curr Treat Options Neurol. 2019 Sep 26;21(10):45.
  3. Vásquez-Codina AY, Leguízamo-Isaza JM, Aborashed-Amador NF, et al. Acute basilar artery occlusion (BAO): a pictorial review of multimodal imaging findings. Emerg Radiol. 2021 Dec;28(6):1205-1212.
  4. Mattle HP, Arnold M, Lindsberg PJ, Schonewille WJ, Schroth G. Basilar artery occlusion. Lancet Neurol. 2011 Nov;10(11):1002-14.

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