COLLATERAL HYPERPLASIA AND CYST FORMATION OF ORBITAL LEPTOMENINX: SECONDARY TO OPTIC-NERVE GLIOMA

Incidental optic nerve sheath arachnoid cyst: A rare case finding with literature review

Arachnoid cysts are the most common benign cystic abnormalities formed due to congenital splitting of the arachnoid layer. They comprise 1% of intracranial masses, and the orbital location is even more rarely reported in history especially in the pediatric population. They might be discovered as an asymptomatic finding on imaging performed for a concomitant condition or, in most reported cases, as a result of ophthalmic impairment. They can be isolated or associated with gliomas, neurofibromas, empty sella syndrome, and frontotemporal porencephalic cysts. Computed tomography scan shows a non-enhancing liquid cystic lesion, and magnetic resonance imaging remains the best assessment tool confirming the similarity of the fluid to cerebrospinal fluid and evaluating the optic nerves. Herein, we report the case of an incidental discovery of an intraorbital arachnoid cyst on magnetic resonance imaging in a 53-year-old woman with a history of epilepsy. No treatment was performed as the cystic formation was asymptomatic.

Arachnoid Cyst of the Optic Nerve

PURPOSE

To describe two patients with arachnoid cysts of the optic nerve mimicking optic nerve/orbital neoplasms.

METHODS

The histories, ophthalmic examinations, and pathologic findings of two patients with arachnoid cysts of the optic nerves were reviewed and compared with previously reported cases.

RESULTS

One patient had progressive proptosis and the other had decreased vision with visual field changes. Pathologic examination of optic nerve sheath biopsies showed redundant proliferations of meningothelial cells with associated thickened dura.

CONCLUSIONS

Arachnoid cysts of the optic nerve are benign, slowly progressive conditions that may result in proptosis and visual field changes. The clinicopathologic features of arachnoid cyst should be differentiated from optic nerve sheath meningioma and other conditions.

Optic nerve coloboma with cyst: a case report and review

A 7-month-old boy presented with strabismus and proptosis of the left eye. He was found to have bilateral optic nerve colobomas associated with cysts arising from the optic nerve sheath and in communication with the subarachnoid space. The evaluation and management of this entity are discussed.

Cysts of the optic nerve three cases associated with meningioma

Cystic enlargement of the optic nerve sheath is extremely rare. Two cases secondary to a small meningioma in the orbital apex and one secondary to an intraorbital optic nerve sheath meningioma are described, a previously unreported association. High resolution CT scans or MRI can delineate quite small lesions in the orbital apex but a small meningioma within the dural sheath may be missed. Patients with an optic nerve cyst without an apparent cause should therefore be scanned over a number of years to exclude the presence of a meningioma.

Surgical treatment of progressive visual loss in traumatic optic neuropathy. Report of two cases

In two patients with traumatic optic neuropathy progressive visual loss was reversed by surgical decompression of the optic nerve sheath. The first patient with hemorrhage beneath the optic nerve sheath had progressive loss of vision from counting fingers to no light perception within 24 hours after the injury. Surgical evacuation of the hematoma improved visual acuity to 8/30. The second patient had progressive visual loss from 20/20 to 20/400 within the 1st week after injury. Drainage of an arachnoid cyst of the optic nerve sheath improved visual acuity to 20/25. Computerized axial tomography disclosed the hemorrhage in the first case and enlargement of the optic nerve sheath in the second. While the management of traumatic optic neuropathy is controversial, surgical intervention for an arachnoid cyst and hematoma involving the optic nerve is clearly beneficial.

Gliomas of the optic nerve or chiasm. Outcome by patients' age, tumor site, and treatment

A review of the literature revealed 623 cases of optic gliomas with sufficient information to permit actuarial (life-table) analysis concerning the prognosis of this disease by the patients' age, tumor site, treatment, and presence of concomitant neurofibromatosis or extension into the hypothalamus or ventricle. All of these factors are important. The development of mathematical models led to the conclusion that these tumors, generally regarded histologically as low-grade astrocytomas, actually have a very wide but continuous range of growth rates. Some grow rapidly enough to be explained by simple exponential doubling at a constant rate, but most behave as though their growth decelerates. Decelerating growth rates make comparisons of various groups of patients difficult. No support is found for the classical hypothesis that some may be hamartomas. Inadequately treated gliomas of the optic nerve or chiasm bear about the same poor prognosis. However, tumors of the optic nerve (intracranial as well as intraorbital) have an excellent prognosis following complete surgical excision and only a slightly poorer prognosis following irradiation. About 5% of optic nerve gliomas recur in the chiasm following "complete" intraorbital excision. Patients with neurofibromatosis have about twice the recurrence rate following complete excision of an intraorbital glioma. Optic chiasmal gliomas appear to respond to irradiation with doses above 4500 rads. Patients with neurofibromatosis have about the same prognosis as patients without neurofibromatosis following irradiation of a chiasmal glioma.

Pilocytic astrocytoma of the optic nerve with hemorrhage and extreme cystic degeneration

Juvenile pilocytic astrocytoma of the optic nerve (glioma of childhood) usually grows slowly. Rapidly evolving proptosis is rare and reflects the accumulation of mucinous or hemorrhagic material within the tumor. Rapid proptosis is more common in those patients beyond the first two decades of life who have long-standing tumors. We studied a 26-year-old woman with rapid proptosis caused by a large blood-filled cyst in a pilocytic astrocytoma of the optic nerve. The cyst was surgically removed along with the intraorbital portion of the optic nerve.

Cyst of the intraorbital optic nerve sheaths

A 43-year-old woman had a history of gradual unilateral visual acuity loss and proptosis. A 2.5-cm cystic dilatation of the intraorbital dura mater was removed. Microscopic examination revealed a vascular proliferation within the leptomeninges. We inadvertently injected the lesion during orbitography, providing us with an unusual radiographic appearance.

Tumors of the optic nerve

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...