Some Answers, Many Questions

Reversible cerebral vasoconstriction syndrome (RCVS) is a fairly recently described constellation of clinical and radiological features: sudden, severe (“thunderclap”) headache; transient, multifocal, segmental vasoconstriction of cerebral arteries lasting several weeks to months; and focal neurological symptoms, sometimes with stroke. The features of what is now called RCVS have been repeatedly recognized, especially since an influential early report by Drs Call and Fleming et al1 published in 1988. A similar syndrome has attracted many different names, depending on whether patients present to specialists in headache, obstetrics, or neurology. These include thunderclap headache with vasospasm, migrainous vasospasm (or “crash” migraine), migrainous angiitis, drug-induced angiitis, postpartum angiopathy, and benign angiopathy of the central nervous system. The label RCVS is an attempt to unify these various descriptions of a distinct clinico-radiological pattern. Nevertheless, there remains uncertainty about the status of RCVS as a true “disease,” which can generally be defined, with progressively less certainty, according to (1) a defined cause; (2) the underlying mechanism (pathophysiology); or (3) a pattern of symptoms and investigation findings (syndrome). As knowledge evolves, some syndromes become more clearly defined by cause or mechanisms, whereas others may not endure. RCVS is a syndrome still in the process of being defined; our understanding and knowledge are increasing as neuroimaging methods improve and more cases are discovered. However, it seems likely that there are many causes (or triggers) for RCVS, and probably more than one underlying pathophysiological mechanism causing abnormal vascular tone. Multiple etiologies …