THE MRI APPEARANCE OF THE OPTIC-NERVE SHEATH FOLLOWING FENESTRATION FOR BENIGN INTRACRANIAL HYPERTENSION

Optic nerve fenestration is carried out in cases of severe benign intr acranial hypertension. This study aimed to monitor the optic nerve she ath appearances and orbital changes that occur following this procedur e. The eight patients were all female with an average age of 37.3 year s and a range of 20-58 years. The duration of symptoms was 2-6 years. Symptoms included headaches, diplopia and visual obscurations. Examina tion revealed severe papilledema. All investigations, including MRI, b iochemical and immunological tests, were negative. Patients had fenest ration of a 2 mm x 3 mm segment of the medial aspect of the optic nerv e sheath. Imaging was obtained with a 1 T MRI machine using a head coi l. Coronal, axial and sagittal 3 mm contiguous sections using STIR seq uences with TR 4900 ms, IT 150 ms and TE 60 ms were obtained. Five pat ients showed clinical improvement. The post-operative MRI findings in four of these included a decreased volume of cerebrospinal fluid (CSF) around the optic nerve sheaths and a localized collection of fluid wi thin the orbit. There were no MRI changes in the three patients with n o clinical improvement. Decreased CSF volume around the optic nerve an d a fluid collection within the orbit may indicate a favorable outcome in optic nerve fenestration.