Neurinoma of the orbit

Primary optic nerve sheath schwannoma: a case report

BACKGROUND

The optic nerve is an unusual site of schwannoma as it lacks Schwannoma cells on it. We report a primary optic sheath schwannoma and to review the literature.

CASE REPORT

A 29-year old female presented with progressive painless non-pulsatile proptosis. Ocular examination revealed only axial proptosis. Imaging showed a well-defined intraconal mass abutting optic nerve. A left frontal craniotomy with orbitotomy and tumor excision was done. The tumor was well encapsulated, posteriorly attached to optic nerve without any plane, probable site of origin. The postoperative duration was uneventful without any complications. The histopathology examination confirms the diagnosis of schwannoma.

CONCLUSIONS

We suggest to consider orbital optic nerve schwannoma in differential diagnosis of orbital tumors despite its exceedingly rare occurrence.

Clinico-Radiological Spectrum and Management of Orbital Schwannomas: A Tertiary Care Institute Study

Abstract Purpose: The aim is to study clinical presentations, radiological features and outcome in histopathologically proven orbital schwannomas. Methods: A retrospective and longitudinal study of 16 patients between January 1999 and July 2011 was undertaken by reviewing the appropriate charts. Clinical and radiological data of all orbital schwannomas patients were analyzed. Results: Mean age was 28.18 years (range 8-40 years). Of 16 patients, 10 were males and 6 females. Duration of symptoms was chronic in 15(93%). Chief complaints were proptosis in 10(62.5%), eyelid swelling in 5(31%) and eyelid mass lesion in 2(12.5%). This included a rare case of cystic schwannoma with microphthalmos. Mass was extraconal in 11(69%). Radiological findings varied from solid to cystic, intraconal to extraconal, no enhancement to intense enhancement and presence of calcification. Thirteen (81%) were excised via anterior orbitotomy route while fronto-orbital craniotomy was done in 3(19%). Postoperatively, vision improved or remained stable in 15(94%) and worsened in one (6%). Final visual acuity of 6/6 was achieved in 11(69%), 6/9 in 2, 6/36 in one. Conclusions: Schwannomas may mimic a variety of mass lesions in the orbit because of variable clinical or imaging features and should be considered in the differential diagnosis of all well circumscribed orbital lesions.

CT findings in orbital tumours of nerve sheath origin

The clinical and CT features of orbital nerve sheath tumours (13 neurofibromas and 17 neurilemmomas, including one malignant neurilemmoma) have been reviewed. The commonest clinical findings were proptosis, mild impairment of visual acuity and disorders of eye movements. No significant correlation with intra- or extraconal location and these symptoms was found. The two types of tumour were morphologically similar, most being smooth retrobulbar masses, elongated in the long axis of the orbit; lobulation was slightly more common with neurofibromas. The neurilemmomas were generally larger than the neurofibromas. The distribution of neurilemmomas in the retrobulbar space, and in its intra- and extraconal compartments appeared random, but most neurofibromas occurred in the upper orbit and three quarters lay extraconally. The apex of the orbit was seen to be clear of tumour in all intraconal neoplasms (except the one case of malignant neurilemmoma); this observation may be useful in differentiation from intrinsic optic nerve tumours and pseudotumour. Focal or generalised enlargement of the bony orbit was common, being seen in four-fifths of neurilemmomas and three-quarters of neurofibromas. Tumour density was homogeneous for all the neurilemmomas and in the majority of neurofibromas: attenuation coefficients were slightly higher for the neurofibromas. Subcutaneous extension was more common in neurofibromas, occurring in approximately one third of cases but was observed in about a tenth of the neurilemmomas. Enhancement with intravenous contrast medium was variable; contrast medium was helpful in showing intracranial extension. Although the CT findings did not allow unequivocal presurgical diagnosis, they were suggestive in many cases and facilitated biopsy.