The cause of thunderclap headache should be considered to be aneurysmal subarachnoid haemorrhage
until proven otherwise. The diagnostic work up involves urgent non-enhanced CT of the brain (with
CT angiography if immediately available), then possibly a lumbar puncture, then cerebral arterial and venous
imaging with either MRI or CT if each preceding investigation has yielded a normal/negative result.
Reversible cerebral vasoconstriction syndrome is usually characterised by recurrent thunderclap headaches
and multifocal, multi-vessel segmental cerebral artery vasoconstriction that usually resolve within 12 weeks.
It can be associated with neurological complications including intracerebral haemorrhage and cerebral
Modern Medicine – April 2018