Protracted Postsurgical Blindness With Visual Recovery Following Optic Nerve Sheath Fenestration

Optic nerve sheath fenestration is an accepted surgical treatment for pseudotumor cerebri when visual loss occurs despite medical therapy. When performed via a medial approach, optic nerve sheath fenestration may require considerable traction on the optic nerve. The nature, severity, and potential reversibility of neural injury caused by sustained rotational traction on an already-compromised optic nerve is unknown. We describe a patient who suffered complete loss of vision in the surgically treated eye following optic nerve sheath fenestration and who subsequently recovered 20/30 visual acuity.

A 22-year-old woman noted headaches, pulsatile tinnitus, and bilaterally blurred vision beginning 2 weeks after the onset of a middle ear infection. She denied pain with eye movements or other neurological symptoms. Physical examination showed an obese woman with a blood pressure of 138/88. Corrected visual acuity was 20/80 OD and 20/70 OS. Both pupils reacted sluggishly to light, and there was no afferent pupillary defect. Eye movements were full. Slitlamp examination through dilated pupils showed no vitreous cells. Fundus examination showed bilateral optic disc swelling with retinal striae and hard exudates extending from the optic discs to the maculas (Figure 1). A lumbar puncture showed an opening pressure of greater than 390 mm of water with normal cerebrospinal fluid chemistry. Systemic and serological evaluations for secondary causes of pseudotumor cerebri were negative. Humphrey 30-2 visual field testing showed concentric constriction of both visual fields to 5° in the right eye and 10° in the left eye (Figure 1). Results of magnetic resonance imaging of the head were normal. The patient was treated with oral acetazolamide, 500 mg, twice daily, and an optic nerve sheath fenestration was performed in the right eye via a medial approach. Several attempts were made to rotate the globe before a successful fenestration was achieved without injury to the optic nerve or its surrounding vessels.

Six hours after the operation, the patient had no light perception in the right eye. Indirect ophthalmoscopy showed persistent optic disc swelling and no retinal abnormalities. Fluorescein angiography showed normal retinal arterial perfusion. Postoperative magnetic resonance imaging showed no signs of orbital or nerve sheath hemorrhage. The patient was treated with intravenous methylprednisolone sodium succinate, 250 mg, 4 times daily, and oral acetazolamide, 500 mg, 4 times daily, but continued to have no light perception in the right eye for 36 hours. During this same period, visual acuity improved to 20/30 OS and the visual field expanded. Thirty-six hours after the operation, she began to identify hand motions with the right eye. After 3 days of treatment with intravenous methylprednisolone, she was discharged from the hospital and was treated with a 3-week tapering dose of oral prednisolone. Following cessation of corticosteroid therapy, her visual acuity was 20/80 OD. Three months after the operation, her visual acuity was 20/30 OD and 20/25 OS. Ophthalmoscopic examination disclosed resolution of papilledema in both eyes and diffuse optic atrophy in the right eye (Figure 2). Visual field testing showed a 5° inferior paracentral island of vision in the right eye and normalization of the visual field in the left eye (Figure 2).

To the best of our knowledge, this is the second published case of visual recovery from total blindness following optic nerve sheath fenestration. Flynn et al¹ described a patient with pseudotumor cerebri who sustained complete loss of vision for a 5-hour period following an optic nerve sheath fenestration that was also performed via a medial approach. Following treatment with intravenous dexamethasone, the visual acuity recovered to 20/800. The authors advocated emergent treatment with intravenous steroids for postsurgical blindness following optic nerve sheath fenestration.

Although complete loss of vision is a recognized complication of optic nerve sheath fenestration,^2,3 the pathophysiology of "tractional" optic neuropathy with late recovery of function has received little attention. The severe preoperative loss of visual field in our patient indicates that there were a limited number of functioning axons in the right optic nerve that could have been damaged by a number of mechanisms. In descending order of likelihood, these include the following: (1) a stretch injury to the optic nerve; (2) ischemia of the optic disc caused by torsion, traction, or repeated abrupt elevations in intraocular pressure; (3) vasospasm of the central retinal artery, posterior ciliary arteries, or both; and (4) postoperative orbital edema. Axonal demyelination from a stretch injury followed by remyelination of affected axons is consistent with our patient's slow recovery of vision over a 3-month period. The influence of high-dose corticosteroid therapy on this patient's visual recovery is uncertain since the visual acuity continued to improve long after cessation of corticosteroid therapy. Although complete loss of light perception is classically held to be a dire prognostic sign, this case demonstrates that protracted postsurgical blindness following optic nerve sheath fenestration does not preclude significant visual recovery.

This article was published in the November issue of the ARCHIVES (1997;115:1473-1474); however, the Humphrey 30-2 visual fields were not printed for both figures. We are now reprinting this article as it should have appeared. The ARCHIVES regrets the error.

Reprints: Michael C. Brodsky, MD, Arkansas Children's Hospital, 800 Marshall St, Little Rock, AR 72202–3591.