SPONTANEOUS INTRACRANIAL HYPOTENSION

Spontaneous intracranial hypotension is a rare but well known entity f irst described by the German neurosurgeon Schaltenbrand. We report the clinical and radiological finding of four patients (2 males, 2 female s, mean age 55 years) presenting with this clinical entity and peculia r constant MRI findings. Intense postural headache was present in all patients together with a very low CSF pressure at lumbar tap although none of the patients had any history of recent lumbar puncture, spinal or cerebral surgery or cranio-cervical trauma. MRI revealed in all pa tients an intense meningeal enhancement and thickening which was most prominent on the dural side of the subdural space. The ventricular sys tem was thin, presenting almost like slit ventricules. A downward shif t of the cerebellar tonsils and hemorrhagic subdural collections were also observed in two patients. Biopsy of meninges performed in two pat ients showed fibrosis of the leptomeninges together with signs of old hemorrhage in one case. We postulate that histologic and radiologic ch anges are due to chronic subdural bleeding in relation with abnormal d isplacement of the nervous structures due to intracranial hypotension. The underlying cause of spontaneous intracranial hypotension is rarel y established and the course of the disease is benign. Some authors ha ve advocated to perform isotopic cysternography in search for a CSF le ak, particularly in the spine, that could be surgically corrected. No such investigation has been conducted yet in our patients because the spontaneous evolution has been mostly favorable.