How often is thunderclap headache caused by the reversible cerebral vasoconstriction syndrome?

Thunderclap headache (TCH) has a broad differential diagnosis that includes the reversible cerebral vasoconstriction syndrome (RCVS). It is believed to be caused by a dysregulation of vascular tone, which leads to reversible and segmental vasoconstriction and may cause permanent neurological deficits. One of the remaining mysteries is the incidence of the syndrome in a general hospital setting.

We recruited consecutive patients with TCH without evidence of aneurysmal subarachnoid hemorrhage on immediate computed tomography-scanning from the emergency room in a period of 12 months. Only those patients with an acute and severe onset of the pain were recruited; the peak of the pain had to be reached in less than 1 minute (verbal analog scale >8/10), and the minimum duration of the pain had to be 6 hours. All patients underwent lumbar puncture, magnetic resonance angiography, and serial transcranial Doppler sonography.

Thirty-four patients fulfilled the inclusion criteria; 3 of those were diagnosed with the RCVS (8.8%; 95%confidence interval 3-23).

We found the incidence of RCVS to be 8.8% (95% confidence interval 3-23) (3 patients) in patients presenting with TCH without evidence for severe illness. We believe that RCVS is an under recognized condition, and there fore additional imaging should be performed in every patient with TCH.