OPTIC NERVE (GLIOMA) ASTROCYTOMA
This rare tumour usually presents in children under 10 years. Up to Optic nerve tumour may one-third, are associated with neurofibromatosis (NFI) where the tumour • __ dumbell though may be bilateral. Tumour growth expands the nerve in a fusiform the Optic manner. Some extend anteriorly into the orbit, others posteriorly '. / * ) /—, foramen, to involve the optic chiasma. All are of the pilocytic type and growth is slow. Clinical features
Visual field scotomas gradually progress to complete visual loss. Orbital extension causes proptosis.
In some patients posterior expansion beyond the chiasma causcs hypothalamic damage (precocious puberty and other endocrine disturbance) and/or hydrocephalus.
X-rays of the orbital foremen show dilatation and CT scans demonstrate an enhancing mixed attenuation mass within the orbit or lying in the suprasellar region. MRI is more sensitive for chiasmatic extensions.
Unilateral within orbit
Lesion involving the optic chiasma
- Complete excision with orbital enucleation if necessary
- Conservative approach (the value of radiotherapy is not known and may risk vasculitis and intellectual deterioration.
- Long-term survival expected.
- Patients may retain vision for many years; survival is often long-term. Those with hypothalamic damage have a poor prognosis.
T1 weighted MRI with gadolinium
Meningiomas arising from the tubcrculum sellae often present early as a result of chiasmal compression causing visual field defects - usually a bitemporal hemianopia.
Straight X-rays may show hyperostosis of the tuberculum sellae or planum sphenoidale.
CT scan shows a rounded, often partly calcified suprasellar mass homogeneously enhancing with contrast. MRI provides improved anatomical detail.
Unfortunately the visual defect often persists after operation, but attempted removal is essential to prevent further progression
Rarely, meningiomas arise from the optic nerve sheath, usually extending in dumbbell fashion through the optic foramen. Some penetrate the orbital dura and invade the orbital contents. Total excision is impossible without sacrificing the adjacent optic nerve.
SUPRASELLAR EPIDERMOID/DERMOID (see page 325).
Note: large aneurysms or granulomas (TB, sarcoid) may simulate a sellar/suprasellar tumour on CT scan or MRI. If in doubt, perform angiography or MRA prior to operative exploration.
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