Is thunderclap headache a separate entity?

Acute severe headache indicative of subarachnoid haemorrhage (SAH), but without the requisite proof, is defined as thunderclap. A special pathophysiological mechanism for the development of this headache is not known as yet. This retrospective study comprised 84 patients. All had the typical clinical signs of a SAH, but cranial computer tomography and lumbar puncture excluded this diagnosis. In 82% of these patients the headache was classified according to aetiologically defined symptomatic groups. One patient with headache of vascular aetiology had an angiographically proven, but not ruptured aneurysm. No definite cause for the headache was found in 18% of cases. None of the patients followed up over a period of between 12 months and 6 years developed SAH or any other severe neurological disorder. 9% reported repeat of the headache event. Thunderclap headache seems to be only a descriptive term for patients with symptoms typical of a SAH without signs of bleeding. Thunderclap headache has no diagnostic or prognostic specificity and therefore we recommend use of this term only as a description of the headache characteristic. Thunderclap headache is not a predictor of a future SAH. Cerebral angiography should be restricted to cases with neurological deficits.