From the anatomical point of view schwannoma of optic nerve is anatomically impossible, as Schwann cells are absent in the optic nerve. However, there were five cases of optic nerve schwannoma had been reported. Among the five cases, three were located in the orbit.
The authors present a case of orbital schwannomaÂ arising from the optic nerve. A 26 year old female presented with gradual decreasing of vision followed byÂ proptosis of the right eye over four years duration. Three weeks before admission the patient was noted totally blind. The globe was straightproptosed with ocular motility was restricted to all direction. There was no perception of light. The pupil was dilated and fixed. The cornea was clear and the sensation was present. There were no birthmarks and family history suggesting neurofibromatosis. CT scan showed an ovoid homogenous enhanced tumor that filled most of the orbit and extended into cavernous sinus through the enlarged superior orbital fissure and into anterior portion of optic canal producing an enlargement of that structure. On the basis of CT scan findings, the preoperative diagnosis in this case included cavernous hemangioma, meningioma and optic nerveglioma.
Frontotemporal craniotomy with orbital osteotomy was performed. The optic canal and the superior orbital fissure were unroofed. The tumor was well encapsulated. Intratumoral decompression and piecemeal capsule resection were done. As the size of the tumor was decreased, the optic nerve just behind the globe was indentified and the medial side of this nerve fused with the mass.Â Posteriorly optic nerve could not be identified due to it was engulfed by tumor itself. Extension of some tumors into superior orbital fissure and cavernous sinus limited their surgical resection. Postoperatively, the patient experienced temporary ptosis and ophthalmoplegia. The pathological report was optic nerve schwannomaÂ .This present case is the fourth case of primary orbital optic nerve schwannoma has ever been reported. Since this tumor originates from optic sheath, decreasing of vision would appeared first. The authors suggest to include orbital optic nerve schwannoma in the differential diagnosis of perioptic tumors although its occurence is exceedingly rare.