Reversible cerebral vasoconstriction syndrome.

Recurrent thunderclap headaches, seizures, strokes, and non-aneurysmal subarachnoid haemorrhage can all reveal reversible cerebral vasoconstriction syndrome. This increasingly recognised syndrome is characterised by severe headaches, with or without other symptoms, and segmental constriction of cerebral arteries that resolves within 3 months. Reversible cerebral vasoconstriction syndrome is supposedly due to a transient disturbance in the control of cerebrovascular tone. More than half the cases occur post partum or after exposure to adrenergic or serotonergic drugs. Manifestations have a uniphasic course, and vary from pure cephalalgic forms to rare catastrophic forms associated with several haemorrhagic and ischaemic strokes, brain oedema, and death. Diagnosis can be hampered by the dynamic nature of clinicoradiological features. Stroke can occur a few days after initial normal imaging, and cerebral vasoconstriction is at a maximum on angiograms 2-3 weeks after clinical onset. The calcium channel blocker nimodipine seems to reduce thunderclap headaches within 48 h of administration, but has no proven effect on haemorrhagic and ischaemic complications.