Background: Thunderclap headache raises the suspicion of subarachnoid haemorrhage, and it is not generally recognised as a symptom of cerebral venous sinus thrombosis (CVST). We describe ten patients who presented with thunderclap headache mimicking subarachnoid haemorrhage, who appeared to have CVST.
Methods: Medical histories of 71 patients who had CVST between 1992 and 1996 were collected. 48 of these took part in a randomised trial of treatment for CVST. The diagnosis was confirmed by conventional angiography or magnetic resonance imaging and angiography in all patients.
Findings: In all ten patients who presented with thunderclap headache, characteristics of the headache and clinical signs and symptoms were clinically indistinguishable from those of subarachnoid haemorrhage. Computed tomography at admission was interpreted as normal in five patients (one with single-dose contrast), as subarachnoid haemorrhage in three, and as multiple intracranial haemorrhages in the remaining patients (one with single-dose contrast). Cerebrospinal fluid (CSF) analysis was done in six patients, and showed erythrocytes and bilirubin in one. CSF pressure was high in the only patient for whom it was measured.
Interpretation: The best initial investigation in patients with thunderclap headache is emergency computed tomography. If no abnormality is detected, lumbar puncture should be done after at least 12 h (to detect or exclude subarachnoid haemorrhage). CSF pressure should be measured. If the CSF pressure is high or if a headache of unknown origin persists, the diagnosis of CVST should be considered.