Tumors of the optic nerve

Abstract

This is a review of primary and secondary tumors of the optic nerve. The emphasis is an optic nerve gliomas and meningiomas. Optic nerve gliomas are slowly growing astrocytic neoplasms of the anterior visual pathways, the majority of which occur within the first two decades of life, with equal sex incidence in about 1 of 200,000 patients presenting with eye complaints. The incidence is greater in neurofibromatosis. The typical presentation is visual impairment in a verbal pre-school child with optic canal enlargement and optic atrophy. An intraorbital location of the tumor leads to axial, irreducible, non-pulsatile proptosis. An intracranial location may disturb hypothalamic and pituitary function and produce hydrocephalus. Ocular findings may also include limited motility on a mechanical-restrictive basis, a pupillary relative afferent defect, nystagmus, and variable, non-specific visual field defects. Roentgenographic studies may show concentric unilateral enlargement of the optic canal with preservation of a well corticated margin, a fossa under the anterior clinoid process in continuity with the optic canal ('J'-shaped sella), and findings of increased intracranial pressure. On pathologic examination the tumor is a smooth, fusiform, intradural enlargement of the optic nerve. Histologically there is proliferation of elongated (pilocytic) astrocytes in reticulated patterns with intervening microcystic spaces containing mucosubstance and surrounding reactive hyperplasia of the arachnoid. Mitoses are not found. The diagnosis is clinical X-ray studies and brain scan should be performed. The differential diagnosis is that of unilateral proptosis in a child and includes acute ethmoiditis, hyperthyrobidism, craniostenosis, other neoplasms, Hand-Schuller-Christian disease, and orbital hemorrhage due to trauma. Surgical resection is performed in cases with unilateral optic nerve involvement, the surgical approach being determined by tumor location. Bilateral or chiasmal cases are treated with radiotherapy when progression occurs. Malignant optic nerve gliomas and optic nerve hyperplasia are also discussed. Optic nerve meningiomas arise from the nerve sheath and are to be distinguished from orbital meningiomas arising from ectopic arachnoidal cells or those secondarily involving the orbit by extension from adjacent sites. Up to 80% of orbital meningiomas occur in females, in two age peaks, 25% in the first decade, and the rest in the 5th decade. Meningiomas present with visual loss and may produce proptosis, papilledema and/or optic atrophy, retinal striae, opticociliary shunts, limitation of extra-ocular movements, and lid edema, Signs of von Recklinghausen's disease should be sought. X-rays are the mainstay of diagnosis. Orbital meningiomas are composed of cells in sheets or in whorls with some spindle shaped cells. Calcifications are typical. Usually the dura is penetrated and the orbit invaded. Primary orbital meningiomas are locally infiltrating but do not metastasize. Complete local excision en bloc is recommended...