Reversible cerebral vasoconstriction syndrome: an important and common cause of thunderclap and recurrent headaches.

Reversible cerebral vasoconstriction syndrome is an intracranial vascular manifestation of a wide variety of diseases. It is the second most common cause of thunderclap headache, the most common cause of recurrent severe secondary headaches, and, in patients <60 years of age, has been reported as the commonest cause of isolated convexity subarachnoid haemorrhage. Radiologically, its key feature is vasoconstriction of the intracranial vessels, a dynamic process that is typically maximal at 2 weeks, varies in its distribution over the course of the disease, and typically resolves after 3 months. It can have haemorrhagic and ischaemic complications and sometimes occurs in concert with posterior reversible encephalopathy syndrome. It also has important associations with dissection and migraine. Rarer atypical cases can present with mild headache, no headache at all, or even a comatose state. This paper provides a detailed review of this syndrome, its pathophysiology, differential diagnosis, imaging findings, and work-up. It also describes the role that high-resolution magnetic resonance imaging (MRI) techniques can have in diagnosing the disease and emphasises the central role that all radiologists have in detecting this important and underdiagnosed condition.