|Year : 1993 | Volume
| Issue : 3 | Page : 128-129
Schwannoma of the orbit
AK Grover, A Rastogi, K Uma Chaturvedi, AK Gupta
Guru Nanak Eye Centre, and Maulana Azad Medical College, New Delhi, India
A K Grover
B-49, New Rajinder Nagar, New Delhi - 110 060.
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Grover A K, Rastogi A, Chaturvedi K U, Gupta A K. Schwannoma of the orbit. Indian J Ophthalmol 1993;41:128-9
Intraorbital neural tumours are rarer compared to similar tumours found in other locations. Schwannomas are seen in only 1% of orbital tumours. By far, all reported cases of Schwannoma of the orbit have been unilateral. To the best of our knowledge, bilateral Schwannomas have not been reported in the literature. We report a case of histologically proven Schwannoma in the right orbit with radiological evidence of a silent tumour in the left orbit which could also be a Schwannoma.
| Case report|| |
A 45-year-old woman presented at Guru Nanak Eye Centre with complaints of slow progressive proptosis in the right eye associated with slight diminution of vision and diplopia for the past 2 1/2 years. There was no history of headache. The visual acuity was 6/18 in the right eye. The ocular movements were restricted. Exophthalmometry revealed a forward proptosis of 8 mm on the right side. No orbital mass could be palpated. The fundus was within normal limits. The left eye was normal. The haemogram, urinalysis, and skiagrams of orbit were within normal limits.
Ultrasonography revealed a retro-ocular mass in the right eye with well-defined margins and good sound transmission. A-scan showed low reflectivity spikes, suggestive of a solid tumour with few intervening septae.
The CT scan [Figure - 1] showed a fusiform well-defined intraconal tumour displacing the optic nerve medially on the right side. A similar tumour on the left side was also seen in the CT scan; however, the radiodensity of this tumour was higher than that of the right side. Contrast studies showed no enhancement in density of the tumour on either side. A benign intraconal spaceoccupying orbital lesion was postulated.
A lateral orbitotomy was performed on the right side by the Berke's incision. A well encapsulated retroocular mass was found separate from the optic nerve, which was easily dissected and excised. Postoperatively, the patient had no diplopia or proptosis. The visual acuity was 6/18.
Histologically, bundles of spindle cells were found with oval monomorphic nuclei. There were areas of nuclear palisading corresponding to Antoni A pattern. In the rest of the areas, a few cells were scattered in a haphazard manner corresponding to Antoni B pattern [Figure - 2]. A diagnosis of neurilemmoma was made.
| Discussion|| |
Schwannomas are slow-growing benign tumours arising from the Schwann cells of peripheral, cranial, sympathetic, and spinal nerves . ,, They are localised and well encapsulated, usually unilateral and rarely malignant. , They are asymptomatic when small  and cause symptoms due to their size. They possess no single diagnostic clinical feature. Ultrasonically an encapsulated solid mass with a well- demarcated anterior border is typically seen. However, CT scan is the most useful preoperative investigative tool. 
Schwannoma of the orbit could occur at any age with no gender predeliction.  The mean age of its occurrence is usually 40 years.
The most common presenting features of Schwannoma of the orbit are exophthalmos, restriction of ocular motility and diplopia. Besides these, pressure effects such as papilloedema and optic atrophy may also be found. Our patient, a 45-year-old woman, had an axial proptosis of 8 mm with slight restriction of ocular movements and diplopia. However, the optic nerve head was normal. Clinically or radiologically, there was no evidence of bony involvement.
The diagnosis of Schwannoma was confirmed by histopathology. In our patient, there was a blend of Antoni A and Antoni B patterns. Classically, the tumour showed compactly arranged spindle cells with abundant eosinophilic cytoplasm and long oval nuclei with thin long axes parallel to one another. The cell margins were poorly demarcated. This pattern conformed to Antoni type-A pattern. A less cellular pattern with haphazardly distributed cells with distinct cytoplasmic margins conformed to Antoni type-B pattern. No features of pleomorphism were seen.
Our patient conforms clinically, ultrasonographically, and histologically with reported cases of Schwannomas. However, the presence of a silent tumour in the left orbit detected radiologically makes this case intriguing. The silent tumour was radiologically considered to be a Schwannoma or a meningioma. The possibility of the silent tumour being a Schwannoma was augmented because it was quite similar to that in the right orbit which proved to be a Schwannoma. However, in view of the fact that the silent tumour was of a different radiodensity, a meningioma could not be ruled out. Certain radiological and clinical features strongly militate against the possibility of a meningioma. The silent tumour was noted to be separate from the optic nerve and no abnormalities were seen in the optic nerve. The silent tumour did not show any enhancement in contrast studies. Also, it is unlikely that a meningioma will remain clinically silent. But Schwannomas are known to remain asymptomatic for a long time. Histological confirmation of the diagnosis was not possible as there was no indication for removal of the silent tumour.
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[Figure - 1], [Figure - 2]