Thunderclap headache (TCH) refers to an excruciating headache of instantaneous onset—as sudden and as unexpected as a “clap of thunder.”3 It is a form of headache that should never be ignored, but should always be thoroughly investigated.
The term "thunderclap headache" was first used to describe this headache as a symptom of an unruptured cerebral aneurysm. Since then, some other disorders have been noted to also present with TCH. Those disorders include:
- subarachnoid hemorrhage (SAH),
- cerebral venous sinus thrombosis (CVST),
- pituitary apoplexy,
- spontaneous intracranial hypotension (SIH),
- hypertensive encephalopathy,
- and retroclival hematoma.
In all of these cases, since the TCH is caused by another disorder, the headache is classified as a secondary headache.
When no organic cause is present, primary thunderclap headache may be diagnosed. Here are the description, diagnostic criteria, and other information from the International Headache Society's International Classification of Headache Disorders, 2nd edition, the gold standard for diagnosing and classifying headache disorders:
4.6 Primary thunderclap headache
Previously used terms: Benign thunderclap headache
4.2 Primary cough headache, 4.3 Primary exertional headache and 4.4 Primary headache associated with sexual activity can all present as thunderclap headache but should be coded as those headache types, not as 4.6 Primary thunderclap headache.
High-intensity headache of abrupt onset mimicking that of ruptured cerebral aneurysm.
- Severe head pain fulfilling criteria B and C
- Both of the following characteristics:
- sudden onset, reaching maximum intensity in less than 1 minute
- lasting from 1 hour to 10 days
- Does not recur regularly over subsequent weeks or months (Note 1)
- Not attributed to another disorder (Note 2)
- Headache may recur within the first week after onset.
- Normal CSF and normal brain imaging are required.
Evidence that thunderclap headache exists as a primary condition is poor: the search for an underlying cause should be expedient and exhaustive. Thunderclap headache is frequently associated with serious vascular intracranial disorders, particularly subarachnoid haemorrhage: it is mandatory to exclude this and a range of other such conditions including intracerebral haemorrhage, cerebral venous thrombosis, unruptured vascular malformation (mostly aneurysm), arterial dissection (intra- and extracranial), CNS angiitis, reversible benign CNS angiopathy and pituitary apoplexy. Other organic causes of thunderclap headache are colloid cyst of the third ventricle, CSF hypotension and acute sinusitis (particularly with barotrauma). 4.6 Primary thunderclap headache should be the diagnosis only when all organic causes have been excluded.