4.4 Primary thunderclap headache

Previously used term:
Benign thunderclap headache.

Coded elsewhere:
4.1 Primary cough headache, 4.2 Primary exercise headache and 4.3 Primary headache associated with sexual activity can all present as thunderclap headache. When such headache is attributed uniquely to one of these triggers, it should be coded accordingly as one of these headache types.

High-intensity headache of abrupt onset, mimicking that of ruptured cerebral aneurysm, in the absence of any intracranial pathology.

Diagnostic criteria:
A. Severe head pain fulfilling criteria B and C
B. Abrupt onset, reaching maximum intensity in <1 min
C. Lasting for ≥5 min
D. Not better accounted for by another ICHD-3 diagnosis.

Evidence that thunderclap headache exists as a primary disorder is poor: the search for an underlying cause should be expedited 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), reversible cerebral vasoconstriction syndrome (RCVS) and pituitary apoplexy. Other organic causes of thunderclap headache are meningitis, colloid cyst of the third ventricle, CSF hypotension and acute sinusitis (particularly with barotrauma). 4.4 Primary thunderclap headache should be a diagnosis of last resort, reached only when all organic causes have been demonstrably excluded. This implies normal brain imaging, including the brain vessels, and/or normal CSF. Of note, vasoconstrictions may not be observed in the early stage of RCVS. For this reason, probable primary thunderclap headache is not a diagnosis that should be made even temporarily.