Sudden Unilateral Neuralgiform Conjunctival Injection Tearing Headache

Sudden Unilateral Neuralgiform Conjunctival Injection Tearing Headache

Sudden unilateral neuralgiform conjunctival injection tearing (SUNCT) headache is an uncommon primary headache disorder that is one of a group of three headache syndromes known as the trigeminal autonomic cephalgias.

Whether SUNCT headache is in fact a distinct headache entity or simply a constellation of symptoms that occurs on a continuum along with the other trigeminal autonomic cephalgias is a point of ongoing debate among headache and pain management specialists.

As with most headache syndromes, the exact cause of the pain of SUNCT headache is unknown; however, the pathogenesis of this uncommon cause of head and face pain is thought to be dysfunction of the trigeminal autonomic reflex.

Trigeminal Autonomic Cephalgias

Cluster headache
Chronic paroxysm hemicranias
Sudden unilateral neuralgiform conjunctival injection tearing headache

The pain of SUNCT headache has a rapid onset to peak, with attacks lasting 5 seconds to 4 minutes and the frequency of attacks ranging from 20 to 200 attacks per day. In some patients, these attacks can be triggered by sensory stimulation of the affected areas, such as when washing the face, brushing the teeth, and so forth.

Although in many ways similar to cluster headache (e.g., unilateral, periorbital, and frontal location of pain, sclera injection, rapid onset to peak, short duration of attacks, and pain-free periods between attacks), SUNCT exhibits many dissimilarities as well.

In contrast to cluster headache, alcohol consumption does not seem to trigger attacks of SUNCT headache, and there do not seem to be the seasonal and chronobiological patterns so characteristic of cluster headache, although SUNCT headache occurs most frequently in the morning and afternoon.

Comparison of Cluster Headache and Sudden Unilateral Neuralgiform Conjunctival Injection Tearing Headache

Comparison FactorsCluster HeadacheSUNCT Headache
Ocular and retroorbital locationYesYes
Rapid onset to peakYesYes
Severe intensityYesYes
Attacks occur in paroxysmsYesYes
Duration of attacks shortYesYes
Pain free between attacksYesYes
Significant rhinorrhea during attacksYesNo
Alcohol triggers attacksYesNo
Tactile trigger areasNoYes
Seasonal pattern of attacksYesNo
Chronobiological pattern of attacksYesNo
Significant eye inflammationNoYes
Responds to sphenopalatine ganglion blockYesNo
Responds to trigeminal nerve blockNoYes

SUNCT, Sudden unilateral neuralgiform conjunctival injection tearing.

Blockade of the sphenopalatine ganglion, which is so effective in the treatment of cluster headache, is of little value in the treatment of SUNCT headache.

Patients suffering from SUNCT headache may respond to daily trigeminal nerve blocks with local anesthetic, as described subsequently.

What are the Symptoms

Patients with SUNCT headache present with the complaint of severe paroxysms of ocular or periorbital pain that radiate into the ipsilateral temple, forehead, nose, cheek, throat, and maxillary region.

This pain is associated with significant inflammation of the affected eye and associated autonomic signs and symptoms. The pain is neuralgiform and severe to excruciating in intensity. SUNCT occurs on the right side 70% of the time in a manner analogous to trigeminal neuralgia. Like trigeminal neuralgia, rare cases of bilateral SUNCT headache have been reported. Also, like trigeminal neuralgia, the pain of SUNCT headache rarely switches sides.

SUNCT headache occurs slightly more frequently in males. It can occur at any age, with a peak incidence in the fifth decade.

Descriptors of Pain Associated With Sudden Unilateral Neuralgiform Conjunctival Injection Tearing Headache


How is Sudden Unilateral Neuralgiform Conjunctival Injection Tearing Headache diagnosed?

Magnetic resonance imaging (MRI) of the brain provides the clinician with the best information regarding the cranial vault, vasculature, and its contents.

MRI is highly accurate and helps identify abnormalities that may put the patient at risk for neurological disasters secondary to intracranial and brainstem pathological conditions, including tumors and demyelinating disease. Magnetic resonance angiography (MRA) also may be useful in helping identify aneurysms, which may be responsible for the patient’s neurological findings.

In patients who cannot undergo MRI, such as patients with pacemakers, computed tomography (CT) is a reasonable second choice. Radionuclide bone scanning and plain radiography are indicated if fracture or bony abnormality such as metastatic disease is considered in the differential diagnosis.

Screening laboratory tests consisting of complete blood cell count, erythrocyte sedimentation rate, and automated blood chemistry testing should be performed if the diagnosis of SUNCT headache is in question. Intraocular pressure should be measured if glaucoma is suspected.

Differential Diagnosis

SUNCT headache is a clinical diagnosis supported by a combination of clinical history, normal physical examination, radiography, and MRI.

Pain syndromes that may mimic SUNCT headache include cluster headache, temporal arteritis, trigeminal neuralgia involving the first division of the trigeminal nerve, demyelinating disease, primary stabbing headache, hypnic headache, and chronic paroxysmal hemicrania, although because of the overlapping features of all headache and facial pain syndromes, SUNCT headache can be easily mistaken for another type of headache or facial pain.

Trigeminal neuralgia involving the first division of the trigeminal nerve is uncommon and is characterized by trigger areas and tic-like movements. Demyelinating disease is generally associated with other neurological findings, including optic neuritis and other motor and sensory abnormalities. The pain of chronic paroxysmal hemicrania lasts much longer than the pain of SUNCT headache.

Differential Diagnosis: Sudden Unilateral Neuralgiform Conjunctival Injection Tearing Headache

Cluster headache
Temporal arteritis
Trigeminal neuralgia
Demyelinating disease
Primary stabbing headache
Hypnic headache
Chronic paroxysmal hemicrania


The treatment of SUNCT headache is analogous to the treatment of trigeminal neuralgia, although the pharmacological management of this uncommon headache disorder is disappointing.

The use of anticonvulsants such as lamotrigine and gabapentin represents a reasonable starting point. High-dose steroids tapered over 10 days also have been anecdotally reported to provide relief. For patients who do not respond to the previously mentioned treatments, daily trigeminal nerve block with a local anesthetic and steroid is a reasonable next step.

Occasionally, retrogasserian injection of glycerol, balloon compression of the gasserian ganglion, and microvascular decompression of the trigeminal nerve root are required to provide palliation of pain. Underlying sleep disturbance and depression associated with the pain of SUNCT headache are best treated with a tricyclic antidepressant compound, such as nortriptyline, which can be started at a single bedtime dose of 25 mg.


Failure to diagnose SUNCT headache correctly may put the patient at risk if an intracranial pathological condition or demyelinating disease, which may mimic the clinical presentation of SUNCT headache, is overlooked. MRI is indicated in all patients thought to have SUNCT headache. Failure to diagnose glaucoma or temporal arteritis, which also may cause intermittent ocular pain, may result in permanent loss of sight.

Clinical Pearls

Trigeminal nerve block with local anesthetic is especially useful in the diagnosis and palliation of pain secondary to SUNCT headache. Given the uncommon nature of this headache syndrome and its overlap with the symptoms of cluster headache and other neurological problems, including cavernous sinus thrombosis and intracranial and retroorbital tumors, SUNCT headache must remain a diagnosis of exclusion.

All patients suspected to have SUNCT headache require MRI of the brain with and without gadolinium contrast material and thorough ophthalmological and neurological evaluation. Trigeminal nerve block should be performed only by clinicians familiar with the regional anatomy.


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