Synopsis
Separate inflammatory cerebral vasculitis from reversible cerebral vasoconstriction syndrome and common mimics, prioritising emergency haemorrhage and stroke assessment before specialist diagnostic and immunosuppressive decisions.
- Reversible cerebral vasoconstriction syndrome typically causes recurrent thunderclap headaches over days to weeks, with or without convexity subarachnoid blood, ischaemic stroke, intracerebral haemorrhage, posterior reversible encephalopathy or seizures.
- RCVS associations include the postpartum period and exposure to vasoactive substances, including sympathomimetics, serotonergic agents, stimulants and some recreational drugs; ask without judgement and document timing.
- Primary angiitis of the central nervous system more often develops subacutely with progressive headache, cognitive or behavioural change, seizures and multifocal neurological deficits rather than repeated stereotyped thunderclaps.
Key red flags
Several abrupt maximal-at-onset headaches separated by partial improvement, especially after exertional or vasoactive triggers, strongly suggests RCVS but retains an emergency vascular differential.
Investigation priorities
Identify subarachnoid or intracerebral blood and assess other urgent structural causes of thunderclap headache.
Management branches
Headache reaches peak intensity within seconds to a minute, whether first or recurrent.
- 1. Stabilise ABCDE, record exact onset and triggers, examine consciousness, meningism, optic discs and focal neurology, and check pregnancy or postpartum status.
- 2. Use the local subarachnoid-haemorrhage imaging pathway and add head-and-neck vascular imaging when RCVS, dissection, aneurysm or stroke is plausible.
Key medicines
Nimodipine for selected RCVSSpecialist centres may use an oral regimen such as 30–60 mg every 4 hours, or an equivalent divided schedule, but this is off-label and must follow local neurovascular advice.
High-dose glucocorticoid for confirmed inflammatory vasculitisInduction may include intravenous methylprednisolone pulses followed by oral prednisolone, with exact dose, taper and additional immunosuppression determined by the specialist vasculitis team.