Orbital Tumors - Optic Nerve Glioma

• Clinical Symptoms

  • decreased visual acuity
  • minimal proptosis
  • restricted, decreased eye movement 
  • strabismus 

• Etiology

  • neoplasm of {the} optic nerve
  • may also be called juvenile pilocytic astrocytoma 
  • Optic nerve glioma in adults are glioblastoma 
  • Optic nerve glioma is {the} most common cause of optic nerve enlargement
    • it accounts for 80% of optic nerve tumors
    • 1% of all intracranial tumors
    • 2% of childhood intraorbital masses

• Demographics

  • 80% are in children under 10 years old
  • peak age is 5-8
  • 90% of patients are under {the} age of 20
  • more common in females
  • 10-50% are in neurofibromatosis patients, especially if bilateral
  • 15% of NF patients have an optic glioma

• Clinical Course

  • Optic nerve gliomas grow very slowly and have similar pathology as juvenile pilocytic astrocytomas of {the} cerebellum. 
  • typically intraorbitally and grow in a fusiform shape 
  • 25% are limited to {the} orbit
  • malignant degeneration is very rare in children
  • if {the} tumor begins in {the} chiasm, it is likely to invade surrounding parenchyma regardless of age

• Imaging

  • On MRI, there is usually mild contrast enhancement. The affected optic nerve should be greater than 3 mm in diameter, or 1 mm wider than {the} unaffected side. It should be hypo- to isointense to muscle on T1 and hyperintense on T2. Fat supression sequences should be performed to see {the} entire extent of {the} lesion since it may possibly appear to be more extensive than it is on T2-weighted images secondary to edema

• Differential Diagnosis

  • Sarcoidosis
  • Infiltration by leukemia or lymphoma
  • Optic neuritis
  • Perineural hematoma
  • Papilledema of intracranial hypertension
  • Patulous subarachnoid space