Long-term follow-up of 71 patients with thunderclap headache mimicking subarachnoid haemorrhage.

Seventy-one patients with sudden, severe, and unusual headache, but with normal computerised tomographic scan and cerebrospinal fluid, were followed for an average of 3.3 years. Twelve patients (17%) had identical recurrences, but again without evidence of subarachnoid haemorrhage. Findings on cerebral angiography, performed in four patients after the first attack and in two patients after recurrent episodes, were normal. Thirty-one (44%) of the seventy-one patients subsequently had regular episodes of tension headache or common migraine. If the computerised tomographic scan and cerebrospinal fluid findings are normal, this type of headache can be regarded as a benign symptom, and cerebral angiography is not indicated.