Headache characteristics in subarachnoid haemorrhage and benign thunderclap headache

One-third of patients with aneurysmal subarachnoid haemorrhage (ASAH) present with headache only. A prompt diagnosis is crucial, but these patients must be distinguished from patients with nonhemorrhagic benign thunderclap headache (BTH). The headache characteristics and associated features at onset in subarachnoid haemorrhage and benign thunderclap headache were studied to delineate the range of early features in these conditions. In this prospective study, 1 of 2 observers interviewed 102 patients with acute severe headache by means of a standard questionnaire. The patients were alert on admission and had no focal deficits. ASAH was subsequently diagnosed in 42 patients, non-aneurysmal perimesencephalic haemorrhage (PMH) in 23 patients, and BTH in 37 patients. Headache developed almost instantaneously in 50 percent of patients with ASAH, 35 percent of patients with PMH, and 68 percent of patients with BTH and within 1 to 5 minutes in 19 percent, 35 percent, and 19 percent, respectively. Loss of consciousness was reported in 26 percent of patients with ASAH, 4 percent of patients with PMH and 16 percent of patients with BTH, and transient focal symptoms in 33 percent, 9 percent, and 22 percent respectively. Seizures and double vision had occurred only in ASAH. Vomiting and physical exertion preceding the onset of headache were more frequent in patients with ASAH (69 percent and 50 percent ) and those with PMH (83 percent and 39 percent) than in those with BTH (43 percent and 22 percent). Headache developed almost instantaneously in only half the patients with aneurysmal rupture and in two thirds of patients with benign thunderclap headache. In patients with acute severe headache, female sex, the presence of seizures, a history of loss of consciousness or focal symptoms, vomiting, or exertion increases the probability of ASAH, but these characteristics are of limited value in distinguishing ASAH from BTH. Aneurysmal rupture should be considered even if focal signs are absent and the headache starts within minutes.