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 might 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