Optic Nerve Schwannoma: A Report of a Rare Case From India and Literature Review

Abstract

Optic nerve schwannoma is a very rarely occurring tumor described in the literature. It is due to the fact that the optic nerve is myelinated by oligodendrocytes. Schwannomas are tumors of the peripheral nervous system, hence optic nerve schwannoma is a rare phenomenon. A 34-year-old patient presented in the outpatient department with complaints of gradual painless protrusion of the left eye (LE) for the past one year. There was no history of diminution of vision. On examination, vision in both eyes was 6/6, anterior segment examination in both eyes was normal, and pupils were central, circular, and reacting to light. Intraocular pressure was measured on a noncontact tonometer and was within normal range. Both eyes' optic disc, fundus, and visual fields were normal. On inspection, axial proptosis was noted in the LE. Proptosis measurement (on Hertel exophthalmometer) in the right eye was 17 mm and in the left eye was 21 mm. MRI of the orbit without contrast was done and showed a well-defined, soft tissue lesion of the optic nerve in the intraconal compartment of the left orbit. Surgical excision of the tumor was done by lateral orbitotomy approach and the tumor was removed in total. Histopathological examination of the mass revealed a benign spindle cell neoplasm suggestive of schwannoma. Postoperatively, proptosis was resolved, 17 mm both in the right and left eye (on Hertel exophthalmometer), and vision in LE remained unchanged (6/6). Postoperatively, intraocular pressure (on noncontact tonometer) was within normal range, and the optic disc, fundus, and visual fields were normal.

Keywords: case report; india; optic nerve sheath; orbital tumors; schwannoma.

Figure 1. Left eye axial proptosis was noted.

On inspection, axial proptosis was noted in the left eye.

Figure 2. MRI of the orbit without contrast.

Figures A (T2-weighted), B (fluid-attenuated inversion recovery), and C (T2-weighted) denoting sagittal, coronal, and axial sections of MRI of the orbit without contrast, respectively, showing a well-defined, oval-shaped, soft tissue lesion in the intraconal compartment in the left orbit.

Figure 3. Intraoperative photograph while removing the mass present in the left orbit.

The mass present in the intraconal compartment in the left orbit was removed surgically by the lateral orbitotomy approach.

Figure 4. A single, greyish-white nodular mass is seen measuring approximately 1.9 x 2 x 1.7 cm.

A single, greyish-white nodular mass measuring approximately 1.9 x 2 x 1.7 cm present in the intraconal compartment of the left orbit was removed by lateral orbitotomy approach.

Figure 5. Histopathological examination slide (HPE) of the mass showing solid area (hypercellular area) and myxoid area (hypocellular area).

Histopathological examination slide (HPE) of the mass showing the solid area (hypercellular, showing Antoni A) and myxoid area (hypocellular, showing Antoni B). The hypercellular area shows spindle cells arranged in an interlacing pattern.

Figure 6. Histopathological examination slide (HPE) of the mass with high magnification of hypercellular area.

Histopathological examination slide (HPE) of the mass shows the hypercellular area with spindle cells arranged in interlacing fascicles and bundles.

Figure 7. Histopathological slide of the mass stained with S-100 stain.

Positive results are indicative of a peripheral nerve sheath tumor.

Figure 8. Image of the patient on postoperative day three following the left eye lateral orbitotomy procedure.

Left eye proptosis was resolved following surgery (image of the patient on postoperative day three).