Primary thunderclap headache

What is primary thunderclap headache

Primary thunderclap headache is a severe headache of sudden onset reaching maximum intensity in less than 1 minute and lasting 5 minutes.

A secondary headache must be excluded with appropriate testing, especially subarachnoid hemorrhage, which is the cause of up to 25% of thunderclap and sentinel headaches.

Headache after subarachnoid hemorrhage typically lasts at least an hour or two. 

These disorders present with thunderclap headaches the following percentages of the time:

  • reversible cerebral vasoconstriction syndrome, 85%;
  • cervical artery dissection, 20%;
  • spontaneous intracranial hypotension, 15%;
  • cerebral venous thrombosis, 2% to 10%.

There are numerous other causes including pituitary apoplexy, retroclival hematoma, ischemic stroke, acute hypertensive crisis, colloid cyst of the third ventricle, meningitis, complicated sinusitis, and subdural hematoma.

Thunderclap headache, which is also known as lone acute severe headache, is an uncommon type of headache that may be the result of an underlying vascular or nonvascular intracranial abnormality or may represent a primary headache syndrome of unknown cause.

Common and uncommon causes of thunderclap headache are listed in the below table. The more benign, though no less painful, primary thunderclap headache occurs over three times more frequently than the serious secondary thunderclap headache.

Because of the often-threatening causes of the less common secondary thunderclap headache (e.g., subarachnoid hemorrhage, cerebral venous thrombosis), urgent evaluation including computed tomography (CT) and/or magnetic resonance imaging (MRI) of the brain and cerebrospinal fluid analysis are indicated in all patients suspected of having thunderclap headache.

Main and Rare Causes of Thunderclap Headache

Main CausesRare Causes
Vascular Disorders
Subarachnoid hemorrhagePituitary apoplexy, arteritis, angiitis
Intracerebral hemorrhageUnruptured vascular malformation, aneurysm
Cerebral venous thrombosisArterial hypertension
Spontaneous intracranial hypotensionCerebral segmental vasoconstriction
Cervical artery dissection
Nonvascular Disorders
Greater occipital neuralgia
Intermittent hydrocephalus by colloid cyst
Meningitis, encephalitisErve virus
Primary Headache Disorders
MigraineCluster headache
Primary thunderclap headacheTension headache, new daily persistent headache
Primary exertional headache
Primary cough headache

Modified from Linn FHH. Primary thunderclap headache. In: Aminoff MJ, ed. Handbook of Clinical Neurology. Vol. 97. New York: Elsevier; 2010:473–481.

One of the most severe headaches encountered in clinical practice, thunderclap headache is characterized by a very rapid onset to peak of less than 1 minute.

The headache may last from 1 to 10 days and, because of its intensity, almost always provokes an urgent trip to the emergency department, where the headache is invariably initially misdiagnosed as the sentinel headache of acute subarachnoid hemorrhage or other potentially catastrophic headache syndromes.

This is not surprising in that primary thunderclap headache is virtually indistinguishable clinically from subarachnoid hemorrhage, one of the most neurologically devastating forms of cerebrovascular accident. Thus, because of the serious consequences of misdiagnosis, by necessity primary thunderclap headache is a diagnosis of exclusion.

Comparison of Primary Thunderclap Headache and Subarachnoid Hemorrhage

Comparison FactorsPrimary Thunderclap HeadacheSubarachnoid Hemorrhage
Severe headacheYesYes
Nausea and vomitingYesYes
Focal neurological signsNoYes
Nuchal rigidityNoYes
Neck and back painNoYes

Diseases That May Mimic Primary Thunderclap Headache

Hypertensive crisis
Loss of spinal fluid
Postdural puncture headache
Spontaneous spinal fluid leak
Collagen-vascular disease
Lupus cerebritis
Cluster headache
Primary exertional headache
Primary cough headache
Ice pick headache
Primary sexual headache

What are the Symptoms of Primary thunderclap headache

As mentioned earlier, primary thunderclap headache is characterized by a very rapid onset to peak of less than 1 minute without obvious inciting factors (e.g., sexual activity, coughing, straining at stool).

The patient with primary thunderclap headache is almost always convinced that he or she is having a stroke and often appears frightened and anxious. The headache of primary thunderclap headache can be located anywhere in the head or neck.

Nausea and vomiting are present approximately 75% of the time. However, the nuchal rigidity and other focal neurological signs often associated with acute subarachnoid hemorrhage and other neurologically devastating syndromes in which severe headache of acute onset are a prominent feature are uniformly absent.

How is Primary thunderclap headache diagnosed?

Testing in patients suspected of having primary thunderclap headache has two immediate goals: (1) to identify occult intracranial pathological conditions or other diseases that may mimic primary thunderclap headache and may require specific urgent treatment and (2) to identify the presence of subarachnoid hemorrhage.

All patients with a recent onset of severe headache thought to be secondary to primary thunderclap headache should undergo emergent CT of the brain to rule out any pathological condition that could be responsible for the patient’s symptoms. Modern multidetector CT scanners have a diagnostic accuracy approaching 100% for subarachnoid hemorrhage if CT angiography of the cerebral vessels is part of the scanning protocol.

Cerebral angiography may also be required if surgical intervention is being considered and the site of bleeding cannot be accurately identified.

MRI of the brain and magnetic resonance angiography (MRA) may be useful if an aneurysm is not identified on CT studies and may be more accurate in the diagnosis of arteriovenous malformations (AVMs).

Screening laboratory tests, including an erythrocyte sedimentation rate, complete blood count, coagulation studies, and automated blood chemistry, should be performed in patients with subarachnoid hemorrhage. Blood typing and crossmatching should be considered in any patient in whom surgery is being contemplated or who has preexisting anemia. Careful serial ophthalmological examination should be performed on all patients with subarachnoid hemorrhage to chart the course of papilledema.

Lumbar puncture is useful in revealing the presence or absence of blood in the spinal fluid, but its utility may be limited by the presence of increased intracranial pressure, making lumbar puncture too dangerous.

Electrocardiographic abnormalities are common in patients with subarachnoid hemorrhage and are thought to be due to abnormally high levels of circulating catecholamines and hypothalamic dysfunction; however, they are rarely present in patients with primary thunderclap headache.

Differential Diagnosis

The differential diagnosis of primary thunderclap headache generally can be thought of as the diagnosis of the lesser of two evils because most of the diseases that mimic primary thunderclap headache are also associated with significant mortality and morbidity. 

The below table lists diseases that may be mistaken for primary thunderclap headache. Prominent among them is subarachnoid hemorrhage, stroke, collagen-vascular disease, infection, neoplasm, hypertensive crisis, spinal fluid leaks, and a variety of more benign causes of headache.


Although no generally accepted treatment for primary thunderclap headache has been defined, the following guidelines may be useful for the clinician when faced with a patient thought to have this uncommon headache syndrome.

First and foremost, if test results reveal no evidence of intracranial pathology or other serious, life-threatening diseases, constant reassurance that the patient does not have a stroke or brain tumor is indicated. In general, drugs used to treat headaches whose primary mechanism of action is vasoconstriction (e.g., ergots, triptans) should be avoided.

Anecdotal reports indicate that intravenous nimodipine may help abort acute attacks and prevent recurrent headache episodes. Gabapentin also has been advocated as a reasonable treatment for primary thunderclap headache and, given its favorable risk-to-benefit ratio, may be a reasonable therapeutic option.


Complications and pitfalls in the diagnosis and treatment of primary thunderclap headache generally fall into three categories. The first category involves the failure to recognize a sentinel bleed associated with subarachnoid hemorrhage and evaluate and treat the patient before significant morbidity or mortality occurs.

The second category involves misdiagnosis that results in unnecessary testing, specifically, cerebral angiography, which itself is associated with significant morbidity and rarely death.

The third category involves iatrogenic morbidity and rarely mortality from the use of medications to treat primary thunderclap headache (e.g., triptans, ergots) that not only do not treat this primary headache syndrome but also have significant side effects.

Clinical Pearls

Primary thunderclap headache is a diagnosis of exclusion.

It is frequently misdiagnosed as the sentinel headache of subarachnoid hemorrhage, causing the treating physician to order urgent diagnostic testing, which is associated with its own significant mortality and morbidity.

The lack of focal neurological findings in a patient with acute headache should point the clinician toward the diagnosis of benign primary headaches including primary thunderclap headache, cough headache, exertional headache, atypical migraine, and headache associated with sexual activity.

This does not mean that urgent computerized scanning of the brain and analysis of the patient’s cerebrospinal fluid are not indicated.


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