Headache as a warning symptom of impending aneurysmal subarachnoid haemorrhage.

About half of the aneurysm patients admitted to neurosurgical departments experience warning symptoms in the form of minor bleeding episodes days or even several months before a major haemorrhage occurs. Headache is the most common symptom of this warning leak, occurring in 9 out of 10 patients. The onset of headache is sudden and is unusual in severity and location, being unlike any headache the patient has otherwise experienced. It is frequently accompanied by transient nausea, vomiting, visual disturbances or meningism. Medical advice may be sought by the patient but all too often the diagnostic importance of a warning headache is missed. It is misinterpreted as attacks of migraine, tension headache, the 'flu, sinusitis, or a "sprained neck". A more vigilant attention to the presence of a warning headache probably offers the greatest opportunity for altering the otherwise serious natural history of aneurysmal subarachnoid haemorrhage. If a warning headache is suspected, lumbar puncture is the examination of choice, once CT scanning has ruled out an intracranial mass lesion.