Spontaneous intracranial hypotension without intracranial hypotension.

A 52-year-old man with a family history of multiple aneurysms presented with the gradual onset of generalized headaches and bilateral sixth nerve palsies. Following intravenous contrast, MRI revealed diffuse pachymeningeal enhancement consistent with spontaneous intracranial hypotension (SIH). Lack of any postural component to the headaches and repeatedly normal opening pressures on lumbar puncture delayed the diagnosis. A cerebrospinal fluid (CSF) leak was not found, but an epidural blood patch led to resolution of symptoms. Although the atypical features of nonorthostatic headache and normal CSF opening pressure have been documented in SIH, and failure to find the site of the leak is not unusual, this case illustrates a confluence of all these findings. An underlying disorder of connective tissue has been linked to SIH, and we propose that decreased meningeal compliance could account for a symptomatic low-volume state of CSF without a low opening pressure.