Optic Pathway Glioma

Optic nerve glioma is a tumor of childhood,20-34 and presentation in adulthood might suggest a more malignant glioma.21 Although the tumor can present at any age, most patients are less than 10 years old with a mean age of 8.8 years. There is no gender predilec-

FIGURE 7.6. (A) Axial non-fat-suppressed MR images show the hy- Note the previously hyperintense fat signal on these Tl-weighted perintense fat on Tl-weighted imaging (B). Axial and (C) coronal images. (D) Metastatic lesion to the right superior rectus muscle. MR studies show fat-suppressed postcontrast Tl-weighted images.

FIGURE 7.6. (A) Axial non-fat-suppressed MR images show the hy- Note the previously hyperintense fat signal on these Tl-weighted perintense fat on Tl-weighted imaging (B). Axial and (C) coronal images. (D) Metastatic lesion to the right superior rectus muscle. MR studies show fat-suppressed postcontrast Tl-weighted images.

tion.34 Optic pathway gliomas are associated with neurofibromatosis type 1 (NF1) (see Chapter 17); the tumor may be asymptomatic in these patients, or appear later in life after initially normal imaging.22,24,25 Some studies have suggested that patients with NF1 may have borderline favorable prognosis, but other studies have shown little or no difference prognosis.26,29,31,33,35

Any part of the optic pathway may be involved with a glioma, and prognosis depends in part upon the extent and location of the tumor. One or both optic nerves alone are involved in 24%, the optic disk is involved in 1.6%, and the optic chiasm or tract is involved in 75%. In general, the more anterior the lesion, the better the prognosis.

Optic pathway gliomas involving the orbit produce proptosis, ophthalmoplegia, and painless progressive visual loss.32 Visual loss is present at presentation in

87.5%. Hypothalamic symptoms (26%) or endocrino-logic manifestations (e.g., diabetes insipidus, diencephalic wasting, precocious puberty, somnolence, growth failure) may occur in chiasmal-hypothalamic tumors.36 Optic disc swelling (35%) or atrophy (59%) is generally present, and rarely optociliary shunt vessels may occur.23

Neuroimaging with an MR scan with gadolinium is superior to CT scan for demonstrating intracranial extension. The imaging typically shows intrinsic enlargement of the optic nerve with variable contrast en-hancement.30,37 Figure 7.8 shows a left optic nerve glioma on an axial fat suppressed MR of the orbit. The treatment of optic pathway gliomas is controversial.38 Most authors recommend a period of observation for progression prior to initiation of therapy as gliomas are often static lesions (after an initial but variable pe-

FIGURE 7.7. T2-weighted MR image of the orbit shows a markedly hypointense lesion (A) consistent with a hypercellular fibrous tumor, in this case solitary fibrous tumor of the right orbit (B).

TABLE 7.3. Systemic or Intracranial Lesions That May Extend

into the Orbit.

Neoplastic

Optic pathway glioma

Secondary intracranial meningioma

or sheath meningioma

Pituitary adenoma

Lymphoproliferative disorders

(e.g., lymphoma and leukemia)

Germinoma

Sinus histiocytosis with

lymphadenopathy

Sinus tumors (e.g., nasopharyngeal

cancer, metastasis, adenoid

cystic carcinoma)

Metastasis

Extramedullary

hematopoiesis

Trauma

Orbital, facial, and skull base fractures

Inflammatory

Sarcoidosis

Wegener's granulomatosis

Collagen vascular disorders

Giant cell arteritis

Orbital inflammatory pseudotumor

Hypertrophic pachymeningitis

Infectious diseases

Mucoceles

Sarcoidosis

Aspergillosis

Mucormycosis

Cysticercosis

Primary bone diseases

Osteopetrosis

Fibrous dysplasia

Craniometaphyseal

Dysplasia

Fibrosclerosis

Paget's disease

Aneurysmal bone cyst

Pneumosinus dilatans

Vascular etiologies

Orbital hemorrhage

Hematic cyst

Subperiosteal hemorrhage

Orbital venous and vascular anomalies

Arteriovenous malformations

Iatrogenic

Intracranial oxidized cellulose

hemostat

Postoperative (e.g., postoptic canal

decompression, sinus surgery)

riod of growth). Radiation therapy is generally reserved for patients over age 5 years with progressive radiographic findings or worsening clinical signs and symptoms.32 The risks of radiation are considerable and include cerebrovascular disease, moya moya disease, cerebral atrophy, subnormal intelligence or learning disabilities, secondary malignancies (e.g., astrocy-tomas), cataracts, radiation retinopathy or optic neuropathy, endocrinopathy, and hypothalmic dysfunc-tion.39-41 These risks are generally higher the younger the age of the patient. Chemotherapy is emerging as a possibly safer alternative to radiation therapy particularly in younger children.32 Various agents and combinations of agents have been used with some anecdotal success including: actinomycin D, vincristine, CCNV, 6-thioguanine, procarbazine, dibromodulatol, topotecan, carboplatin, and etoposide.32

FIGURE 7.8. Axial fat-suppressed T1-weighted postcontrast MR scan of the orbit shows a left fusiform enhancing optic nerve mass consistent with an optic nerve glioma.

Surgical therapy is generally limited. A strictly optic nerve glioma with no useful vision or progression may be resected. Chiasmal, hypothalamic, or optic tract gliomas, cannot be completely resected because of unacceptable visual and surgical morbidity. Any exophytic and symptomatic component of these tumors, however, may be debulked. Secondary hydrocephalus may require shunting procedure.32

The prognosis of optic pathway gliomas is quite variable and is in part based upon location.42 Most (80%) have stable vision after an initial period of visual loss. The 10-year overall survival rate is between 85% to 100% in various series, and spontaneous regression may occur.27,28

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