BASICS

DESCRIPTION

• Most common infiltrative lesion of the optic nerve (ON).

EPIDEMIOLOGY

Incidence

• 1% of all intracranial tumors

• 3% of orbital tumors

• 4% of all gliomas

• Occurs in 15% of patients with NF1

• Represents 65% of intrinsic optic nerve tumors

• 90% recognized by second decade of life

• Also known as optic pathway glioma (OPG)

RISK FACTORS

• Neurofibromatosis type 1 (NF1) in 25–30% of cases of OPG.

Genetics

• Localized to chromosome 17 if associated with NF1 (autosomal dominant)

GENERAL PREVENTION

• N/A

PATHOPHYSIOLOGY

• Progressive growth with infiltration and compression of the ON, producing visual loss

– May affect ON anywhere along its course from globe through optic tract

ETIOLOGY

• Neoplastic infiltration of ON

COMMONLY ASSOCIATED CONDITIONS

• NF1 present in 25–30% of OPG

DIAGNOSIS

HISTORY

• Progressive painless visual loss +/− proptosis and/or diplopia

• History of NF1

PHYSICAL EXAM

• Demonstrates features of an optic neuropathy: Decreased visual acuity, decreased color vision, nerve fiber bundle-type visual field defects though may have temporal defects or homonymous defect if concurrent involvement of the optic chiasm or tract respectively, afferent pupillary defect if unilateral or asymmetric optic nerve involvement

• Optic nerve may be pale or edematous based upon location of tumor with anterior involvement producing ON edema while posterior orbital, canalicular, or intracranial lesions demonstrate ON pallor

• May have proptosis, strabismus, or nystagmus

• May have stigmata of NF1 (e.g., Lisch nodules, café au lait spots, dermal neurofibromas)

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