Spontaneous intracranial hypotension: a cause of severe acute headache.

Severe acute headache is a common presenting symptom to an accident and emergency department. Spontaneous intracranial hypotension (SIH) is an increasingly recognised cause of these symptoms and has characteristic clinical and imaging findings. SIH is characterised by headache worse on standing, low opening cerebrospinal fluid pressures at lumbar puncture and uniform pachymeningeal enhancement with gadolinium enhanced magnetic resonance imaging of the brain, all in the absence of dural trauma. Atypical presentations occur and severe neurological decline can rarely be associated with this condition. A review of five patients presenting recently to our institution with classical imaging findings together with a review of the literature is presented.