Reversible cerebral vasoconstriction syndrome as a cause of thunderclap headache: a retrospective case series study.

Thunderclap headache is a common emergency department presentation. Although subarachnoid hemorrhage (SAH) should be the first diagnosis to exclude, reversible cerebral vasoconstriction syndrome (RCVS) is an important alternative cause, which may be commoner than appreciated. Reversible cerebral vasoconstriction syndrome is characterized by multifocal narrowing of cerebral arteries, typically manifested by acute, severe headache with or without neurologic deficits. To compare and discuss the clinical and radiologic characteristics of patients with RCVS. We report 4 cases of RCVS, presenting at a single unit in 1 year. All presented with thunderclap headache, whereas half of them had additional neurologic symptoms such as right homonymous hemianopia, right-sided weakness, and slurred speech. Brain computed tomography was normal in 2 of our patients, but subsequent cerebrospinal fluid analysis revealed xanthochromia consistent with SAH. The remaining 2 patients demonstrated intracerebral hemorrhage on computed tomography. All of our patients underwent digital subtraction angiography that showed segmental narrowing and dilatation of one or more cerebral arteries without any signs of aneurysm. Repeat digital subtraction angiography after 3 months was entirely normal prompting the diagnosis of RCVS. Thunderclap headache requires urgent workup to identify the underlying cause. Although SAH is the most important diagnosis to exclude in the first instance, emergency physicians should be aware of other causes and how they present, such as RCVS. Early recognition of this condition is important in order to remove precipitants, avoid unnecessary investigations, and inform patients about their prognosis.