Subdural haematoma: a potentially serious consequence of spontaneous intracranial hypotension.

BACKGROUND Spontaneous intracranial hypotension (SIH) is characterised by postural headache and low opening pressure at lumbar puncture without obvious cause. Cranial magnetic resonance imaging often shows small subdural collections without mass effect, dural enhancement, venous sinus dilatation, or downward displacement of the brain. The condition is thought to be benign. OBJECTIVES To evaluate the incidence of subdural haematoma as a serious complication of SIH. METHODS A prospective survey of all cases of SIH presenting to a large neuroscience unit over a two year period. RESULTS Nine cases of SIH were seen. Four of these were complicated by acute clinical deterioration with reduced conscious level because of large subdural haematomas requiring urgent neurosurgical drainage. CONCLUSIONS SIH should not be considered a benign condition. Acute deterioration of patients' clinical status may occur secondary to large subdural haematomas, requiring urgent neurosurgical intervention.