Optic nerve sheath fenestration in pseudotumor cerebri. A lateral orbitotomy approach.

In patients with pseudotumor cerebri accompanied by loss of vision, optic nerve sheath fenestration is an effective route to prompt recovery of vision. A lateral orbitotomy approach to decompression of the optic nerve is appropriate for the ophthalmologist with adequate orbital experience. A rectangular window of dura and arachnoid, measuring approximately 3 X 5 mm, is excised from the bulbous portion of the optic nerve. It is important that the arachnoid within the window is excised because an intact arachnoid is an effective barrier to cerebrospinal fluid egress. The use of operating microscope, microsurgical instrument, and microdissecting techniques are emphasized. Twenty-eight patients (40 eyes) with progressive visual loss were treated by surgical nerve sheath fenestration. A study of the indications, results, and complications of this procedure is presented in a companion article.