Thunderclap headache: is it migraine?

In a prospective study, 14 out of 49 patients presenting to a Regional Neurosurgical Unit with sudden headache suggestive of subarachnoid haemorrhage had normal CSF and a normal CT scan: it did not prove possible, on clinical grounds alone, to distinguish these from those that had bled. We have now followed all these patients for a minimum of 18 months. Only one has had no further headache, 4 have had musculoskeletal pain, 5 psychogenic pain, and 4 migraine type symptoms. None went on to have an unequivocal subarachnoid haemorrhage, and we conclude that angiography cannot be justified in patients with this type of "thunderclap headache".