Benign neural and osseous lesions

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Neurilemmomas (Schwannomas) typically present like cavernous haemangioma and have a similar scan appearance, and neurofibromas usually form a mass in the supraorbital nerve, with slowly progressive proptosis and hypoglobus; resection of these tumours, when causing loss of orbital function, is curative. In contrast, plexiform neurofibromas diffusely affect the anterior orbital tissues, especially in the upper eyelid and lacrimal gland, and resection is difficult and does not eliminate the disease.

Primary optic nerve tumours, either meningioma or glioma, are usually benign and present in childhood or young adults. Gliomas cause proptosis and mild visual loss and CT scan shows a fusiform enlargement of the optic nerve (Figure 12.16); MRI is particularly useful for demonstrating changes in the intracanalicular and intracranial portions of the nerve. Gliomas require neurosurgical resection, if progressing to threaten the optic chiasm, or orbital resection if causing gross proptosis. Optic nerve meningiomas do not cause significant proptosis, but profound visual failure due to impairment of optic nerve perfusion. CT scan typically shows a diffuse expansion of the optic nerve and, in some cases, calcification within the optic nerve sheath (Figure 12.17) and MRI may demonstrate a normal or small nerve passing through an enlarged sheath. Neurosurgical resection of optic nerve meningiomas may be considered in younger people, in whom the tumour appears to have a more active course and risks intracranial involvement.

There are many rare diseases that affect the orbital bones, but the commonest is sphenoid wing meningioma. This tends to present in middle age with chronic variable lid swelling, chemosis and mild proptosis. The CT scan shows hyperostosis of the greater wing of the sphenoid with en-plaque soft tissue on the lateral wall of the orbit, the temporalis fossa or the middle cranial fossa (Figure 12.18). Although a metastasis may very rarely present with a similar radiological appearance, the

Figure 12.16 Optic nerve glioma causing fusiform enlargement of the nerve.
Figure 12.17 Elongated enlargement of the optic Figure 12.18 Hyperostosis and soft tissue mass of nerve, with linear calcification, due to primary optic sphenoidal wing meningioma: (a) axial soft tissue, (b) nerve meningioma: (a) axial view, (b) coronal view. bone CT scan windows.

clinical behaviour is different - with sphenoid wing meningioma progressing very slowly and usually not requiring any active treatment; biopsy is indicated if a rapid progression is suggestive of metastatic disease.

Further reading

Ferguson MP, McNab AA. Current treatment and outcome in orbital cellulitis. Aust NZ J Ophthalmol 1999; 27:375-9. Harris GJ. Subperiosteal abscess of the orbit: computed tomography and the clinical course. Ophthal Plast Reconstr Surg 1996; 12:1-8. Harris GJ, Logani SC. Eyelid crease incision for lateral orbitotomy. Ophthal Plast Reconstr Surg 1999; 15:9-16. Harris GJ, Sokol PJ, Bonavolonta G, De Conciliis C. An analysis of thirty cases of orbital lymphangiomas. Pathophysiologic considerations and management recommendations. Ophthalmology 1990; 97:1583-92. Katz BJ, Nerad JA. Ophthalmic manifestations of fibrous dysplasia: a disease of children and adults. Ophthalmology 1998; 105:2207-15.

Lacey B, Chang W, Rootman J. Nonthyroid causes of extraocular muscle disease. Surv Ophthalmol 1999; 44:187-213.

Lacey B, Rootman J, Marotta TR. Distensible venous malformations of the orbit: clinical and hemodynamic features and a new technique for management. Ophthalmology 1999; 106:1197-209. McNab AA, Wright JE. Cavernous haemangiomas of the orbit. Aust NZ J Ophthalmol 1989; 17:337-45. McNab AA, Wright JE. Lateral orbitotomy - a review. Aust

NZ J Ophthalmol 1990; 18:281-6. McNab AA,Wright JE. Orbitofrontal cholesterol granuloma.

Ophthalmology 1990; 97:28-32. McNab AA, Wright JE, Casswell AG. Clinical features and surgical management of dermolipomas. Aust NZ J Ophthalmol 1990; 18:159-62. Miszkiel KA, Sohaib SAA, Rose GE, Cree IA, Moseley IF. Radiological and clinicopathological features of orbital xanthogranuloma. Br J Ophthalmol 2000; 84:251-8. Nugent RA, Lapointe JS, Rootman J, Robertson WD, Graeb DA. Orbital dermoids: features on CT. Radiology 1987; 165:475-8.

Rootman J. Why "orbital pseudotumour" is no longer a useful concept. Br J Ophthalmol 1998; 82:339-40.

Rootman J, Hay E, Graeb D. Orbital adnexal lymphangiomas: a spectrum of hemodynamically isolated vascular hamartomas. Ophthalmology 1986; 93:1558-70.

Rootman J, Kao SC, Graeb DA. Multidisciplinary approaches to complicated vascular lesions of the orbit. Ophthalmology 1992; 99:1440-6.

Rootman J, McCarthy M, White V, Harris G, Kennerdell J. Idiopathic sclerosing inflammation of the orbit. A distinct clinicopathologic entity. Ophthalmology 1994; 101:570-84.

Rose GE. Suspicion, speed, sufficiency and surgery: keys to the management of orbital infection. Orbit 1998; 17:223-6.

Rose GE, Hoh B, Harrad RA, Hungerford JL. Intraocular malignant melanomas presenting with orbital inflammation. Eye 1993; 7:539-41.

Rose GE, Wright JE. Isolated peripheral nerve sheath tumours of the orbit. Eye 1991; 5:668-73.

Rose GE, Wright JE. Pleomorphic adenomas of the lacrimal gland. Br J Ophthalmol 1992; 76:395-400.

Sathananthan N, Moseley IF, Rose GE, Wright JE. The frequency and significance of bone involvement in outer canthus dermoid cysts. Br J Ophthalmol 1993; 77:789-94.

Shields JA, Kaden IH, Eagle RC Jr, Shields CL. Orbital dermoid cysts: clinicopathologic correlations, classification, and management. The 1997 Josephine E. Scheler Lecture. Ophthal Plast Reconstr Surg 1997; 13:265-76.

Shields JA, Bakewell B, Augsberger JJ et al. Classification and incidence of space occupying lesions of the orbit: A survey of 645 biopsies. Arch Ophthalmol 1984; 102:1606-11. Sullivan TJ, Wright JE, Wulc AE, Garner A, Moseley IF, Sathananthan N. Haemangiopericytoma of the orbit. Aust NZ J Ophthalmol 1992; 20:325-32. Wright JE, McNab AA, McDonald WI. Primary optic nerve sheath meningioma. Br J Ophthalmol 1989; 73:960-6. Wright JE, McNab AA, McDonald WI. Optic nerve glioma and the management of optic nerve tumours of the young. Br J Ophthalmol 1989; 73:967-74. Wright JE, Sullivan TJ, Garner A, Wulc AE, Moseley IF. Orbital venous anomalies. Ophthalmology 1997; 104:905-13.

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