Pilocytic Astrocytoma (Optic Glioma)

    • Congenital low-grade (WHO Grade 1) astrocytoma of the optic nerves, optic chiasm, and hypothalamus (“optic glioma”)
    • Usually discovered before age 20 years
    • Neurofibromatosis type 1 is present in 30–50%
    • Present in 15% of patients with neurofibromatosis type 1  
    • MRI shows an intrinsic mass in the optic nerve, optic chiasm, and/or hypothalamus
    • No biopsy is necessary if imaging is distinctive
    • Chemotherapy is often used but its benefit is uncertain as controlled trials have not been performed
    • Surgical resection of the optic nerve is reserved for unsightly proptosis when the affected eye has no light perception
    • Core clinical features
      • Stationary or progressive visual loss in one eye or both
      • Reduced visual acuity and visual field defects in one or both eyes
      • Afferent pupil defect
      • Optic discs appear normal or pale (or elevated if an orbital tumor involves the distal optic nerve)
    • Possible accompanying clinical features
      • Monocular pendular nystagmus (often vertical)
      • Seesaw nystagmus
      • Proptosis (if there is a large tumor in the orbit)
      • Iris hamartomas called “Lisch nodules” (sign of neurofibromatosis Type 1) should be present if the patient is aged above 10 years
      • Eyelid plexiform neuroma
    • Imaging features
      • Brain/orbit MRI shows enlargement or signal alteration within the optic nerve, optic chiasm, and/or hypothalamus
      • Tip: pilocytic astrocytoma is unusual among optic nerve lesions in causing marked enlargement of the nerve and/or chiasm together with avid enhancement
    • Other orbital and sellar region tumors
    • Optic neuritis
    • Neuromyelitis optica
    • Lymphocytic hypophysitis
    • Sarcoidosis
    • Metastatic cancer
    • Hematopoietic cancers, including lymphoma
    • Langerhans cell histiocytosis
    • Order orbit-based MRI, which is usually diagnostic
    • Biopsy the lesion only if the imaging features are not classic or a large exophytic component is present
    • Tumor size and visual function often remain stable in untreated patients
    • Visual decline may be caused either by tumor growth, tumor production of extracellular matrix, or reactive meningeal hyperplasia
    • Intraorbital tumors may have an intracranial component, but they do not spread intracranially
    • Trap: do not treat a tumor apparently confined to the orbit, except when there is disfiguring proptosis and a blind eye, in which case excision of the intraorbital optic nerve, sparing the eye and extraocular muscles, may be indicated
    • Place a ventriculoperitoneal shunt for obstructive hydrocephalus
    • Consider chemotherapy for patients under age 9 whose tumors are growing, involving the optic chiasm or hypothalamus, causing severe vision loss, worsening vision, or hypothalamic dysfunction
    • Trap: there are no controlled trials to affirm that chemotherapy is effective in this condition
    • Prescribe chemotherapy for patients under age 9 whose tumors are growing or involve the optic chiasm and/or hypothalamus, and are causing severe or worsening vision or hypothalamic dysfunction
    • Consider radiation therapy as an alternative to chemotherapy for patients older than 9 years
    • Trap: radiation therapy in patients with NF 1 carries a high risk of later occlusive vasculopathy and secondary tumors
    • These tumors may rarely cause severe neuroendocrine morbidity or death

    Optic Nerve And Chiasm Disorders

    Drusen Optic Neuropathy Colobomatous Optic Neuropathy Optic Pit Neuropathy Morning Glory Optic Neuropathy Hypoplastic Optic Neuropathy Typical Optic Neuritis Atypical Optic Neuritis Papillitis (Neuroretinitis) Non-arteritic Ischemic Optic Neuropathy Arteritic Ischemic Optic Neuropathy Posterior Ischemic Optic Neuropathy Hypotensive Ischemic Optic Neuropathy Radiation-induced Optic Neuropathy Diabetic Papillopathy Hypertensive Optic Disc Edema Papilledema Idiopathic Intracranial Hypertension (Pseudotumor Cerebri) Compressive Optic Neuropathy: Overview Optic Neuropathy of Graves Disease Optic Nerve Sheath Meningioma Sphenoid Meningioma Craniopharyngioma Pituitary Adenoma Pilocytic Astrocytoma (Optic Glioma) Carotid Aneurysm Suprasellar Germinoma Infiltrative (Neoplastic) Optic Neuropathy Paraneoplastic Optic Neuropathy Traumatic Optic Neuropathy Toxic Optic Neuropathy Nutritional Deficiency Optic Neuropathy Dominantly-Inherited Optic Neuropathy Leber Hereditary Optic Neuropathy Primary Open Angle Glaucoma