Spontaneous intracranial hypotension mimicking aneurysmal subarachnoid hemorrhage

OBJECTIVE: An excruciating headache of instantaneous onset is known as a th underclap headache, A subarachnoid hemorrhage is the prototypical cause, bu t other serious disorders may also present with a thunderclap headache, inc luding cerebral venous sinus thrombosis, carotid artery dissection, and pit uitary apoplexy. We report a group of patients with thunderclap headaches a s the initial manifestation of spontaneous intracranial hypotension caused by a spinal cerebrospinal fluid leak. METHODS: Among 28 patients with spontaneous intracranial hypotension due to a documented spinal cerebrospinal fluid leak, four (14%) initially experie nced an excruciating headaches of instantaneous onset. RESULTS: The mean age of the four patients (two men and two women) was 35 y ears (range, 24-45 yr), Nuchal rigidity was present in the three patients w ho sought early medical attention, and they underwent emergency computed to mographic scanning, lumbar puncture, and cerebral angiography to rule out a n aneurysmal subarachnoid hemorrhage. The delay between the onset of headac he and diagnosis of intracranial hypotension ranged from 4 days to 5 weeks. A fourth patient did not seek medical attention until 1 month after the ic tus. CONCLUSION: Spontaneous intracranial hypotension should be included in the differential diagnosis of thunderclap headache, even when meningismus is pr esent.