Computed Tomography
Findings
- In children, unenhanced CT scans typically reveal a marked, diffuse enlargement of the optic nerve, with characteristic kinking or bending. The enlargement may be tubular, fusiform, or excrescent.
- Areas of lucency may result from mucinous or cystic changes.
- Approximately 50% of the lesions demonstrate enhancement; this characteristic is more common with intracranial (especially retrochiasmatic) extension.
- Calcifications are rare.
Degree of Confidence
The diagnosis may be made with a high degree of confidence when the lesion involves the optic chiasm and retrochiasmatic optic pathway.
When confined exclusively to the orbit, the lesion may mimic optic neuritis or optic nerve meningioma; in this setting and in most instances, MRI is a better diagnostic tool than is CT scanning.
CT scanning is the better modality for identifying uncommon meningioma with flecks of calcification, which are rare in optic nerve glioma.
False Positives/Negatives
False-positive results can occur because of unilateral optic nerve enhancement or other unilateral disorders, such as optic meningioma, vascular lesions, neuritis, pseudotumor, and sarcoidosis. In addition, subtle nerve enhancement occasionally may develop in normal individuals.
Improper examination techniques, including failure to administer contrast or obtain thin sections, can lead to a false-negative diagnosis.
Magnetic Resonance Imaging
Coronal noncontrast T1-weighted MRI reveals a large intraorbital mass (arrow) centered on the optic nerve.
Coronal postgadolinium T1-weighted MRI with fat saturation (same patient as in Image above) reveals diffuse, intense enhancement of the intraorbital mass (arrow).
Axial postgadolinium T1-weighted MRI with fat saturation (same patient as in Images above) reveals diffuse, intense enhancement of the intraorbital mass. The lesion is confined to the orbit.
Axial postgadolinium T1-weighted MRI with fat saturation in a 6-year-old girl demonstrates enhancement of the intracranial optic nerve (arrow), which is slightly expanded.
Axial noncontrast T1-weighted MRI reveals bilateral, fusiform enlargement of the optic nerves (arrows) in a 14-year-old patient with neurofibromatosis type 1, consistent with bilateral optic nerve gliomas.
Axial noncontrast T1-weighted MRI in a 46-year-old man demonstrates enlargement of both optic tracts (arrowheads) and the optic chiasm (arrow).
Axial T2-weighted MRI in a 46-year-old man demonstrates a mass in the lateral geniculate nucleus of the thalamus resulting from contiguous extension of the patient's known optic nerve glioma.
Findings
- On T1-weighted images, optic nerve gliomas are usually isointense to the cortex and hypointense to white matter (Image 1).
- Invariably, the lesions are hypointense to orbital fat (Image 1).
- On T2-weighted images, lesions demonstrate a mixed appearance that is isointense to hyperintense relative to white matter and the cortex.
- Following contrast administration, intense enhancement is common (Images 2-4).
- A diagnosis of NF-1 may be supported by several findings including the following:
- Bilateral optic nerve gliomas (Image 5)
- Spongiform changes (hyperintensity on T2-weighted images) in the cerebellum, brain stem, basal ganglia, thalamus, periventricular white matter, and corpus callosum
- Adult lesions may involve the orbital, intracanalicular, or prechiasmal portions of the optic nerve, resulting in enlargement; they may exhibit retrochiasmatic extension as well (Images 6-7).
- Usually, the lesions are hypointense to isointense relative to the optic nerve on T1-weighted images and are hyperintense to it on T2-weighted images. Enhancement is uniform and intense.
Patients without NF-1 demonstrate cystic components more commonly at T2 -weighted imaging.9
Degree of Confidence
The diagnosis may be made with a high degree of confidence when the lesion involves the optic chiasm and retrochiasmatic optic pathway.
When confined exclusively to the orbit, the lesion may mimic optic neuritis, pseudotumor, lymphoma, or optic nerve meningioma. Classically, meningioma, the primary differential diagnostic consideration, is characterized by the "tram-track" sign, with enhancement of the periphery of the nerve–optic sheath unit. On the other hand, enhancement in optic nerve glioma is more uniform. Isolated enlargement of the optic nerve sheath also may present diagnostic difficulty; however, this enlargement can usually be distinguished by its signal characteristics, which follow fluid signal on all MRI pulse sequences.
In most instances, including those described above, the diagnosis can be made with greater confidence using MRI than it can with CT scanning.
False Positives/Negatives
A false-positive diagnosis can occur as a result of unilateral optic nerve enhancement or other unilateral disorders, such as optic meningioma, vascular lesions, neuritis, pseudotumor, lymphoma, and sarcoidosis. In addition, subtle nerve enhancement occasionally may develop in normal individuals.
Improper examination techniques, including failure to administer contrast, use fat saturation, or obtain thin sections, can result in a false-negative diagnosis.
More on Optic Nerve Glioma |
| Overview: Optic Nerve Glioma |
 Imaging: Optic Nerve Glioma |
| Follow-up: Optic Nerve Glioma |
| Multimedia: Optic Nerve Glioma |
| References |
| Further Reading |
| « Previous Page | Next Page » |
References
Wilhelm H. Primary optic nerve tumours. Curr Opin Neurol. Feb 2009;22(1):11-8. [Medline].
Aoki S, Barkovich AJ, Nishimura K, et al. Neurofibromatosis types 1 and 2: cranial MR findings. Radiology. Aug 1989;172(2):527-34. [Medline].
Hendrix LE, Kneeland JB, Haughton VM, et al. MR imaging of optic nerve lesions: value of gadopentetate dimeglumine and fat-suppression technique. AJNR Am J Neuroradiol. Jul-Aug 1990;11(4):749-54. [Medline].
Messori A, Salvolini U. Hybrid phakomatosis: from initial CT observation to molecular studies. AJNR Am J Neuroradiol. Aug 2004;25(7):1297-8.
Listernick R, Charrow J, Greenwald MJ, et al. Optic gliomas in children with neurofibromatosis type 1. J Pediatr. May 1989;114(5):788-92. [Medline].
Hollander MD, FitzPatrick M, O''Connor SG, et al. Optic gliomas. Radiol Clin North Am. Jan 1999;37(1):59-71, ix. [Medline].
Millar WS, Tartaglino LM, Sergott RC, et al. MR of malignant optic glioma of adulthood. AJNR Am J Neuroradiol. Sep 1995;16(8):1673-6. [Medline].
Thiagalingam S, Flaherty M, Billson F. Neurofibromatosis type 1 and optic pathway gliomas: follow-up of 54 patients. Ophthalmology. Mar 2004;111(3):568-77. [Medline].
Kornreich L, Blaser S, Schwarz M, et al. Optic pathway glioma: correlation of imaging findings with the presence of neurofibromatosis. AJNR Am J Neuroradiol. Nov-Dec 2001;22(10):1963-9. [Medline].
Tumialan LM, Dhall SS, Biousse V. Optic nerve glioma and optic neuritis mimicking one another: case report. Neurosurgery. Jul 2005;57(1):E190; discussion E190.
Taylor T, Jaspan T, Milano G, Gregson R, Parker T, Ritzmann T, et al. Radiological classification of optic pathway gliomas: experience of a modified functional classification system. Br J Radiol. Oct 2008;81(970):761-6. [Medline].
Forte R, Cennamo G, Breve MA. Three-Dimensional Ultrasound of Ophthalmic Pathologies. Ophthalmologica. Jan 31 2009;223(3):183-187. [Medline].
Walrath JD, Engelbert M, Kazim M. Magnetic resonance imaging evidence of optic nerve glioma progression into and beyond the optic chiasm. Ophthal Plast Reconstr Surg. Nov-Dec 2008;24(6):473-5. [Medline].
Buffa A, Vannelli S, Peretta P. [NF1 and gliomas: the importance of the MRI]. Minerva Pediatr. Apr 2008;60(2):259-60. [Medline].
Kwon Y, Bae JS, Kim JM. Visual changes after gamma knife surgery for optic nerve tumors. Report of three cases. J Neurosurg. Jan 2005;102 Suppl:143-6.
Further Reading
Related eMedicine topics
Neurofibromatosis Type 1 (from Radiology)
Neurofibromatosis, Type 1 (from Neurology)
Optic Neuropathy, Compressive
Sudden Visual Loss (from Neurology)
Sudden Visual Loss (from Ophthalmology)
Clinical guidelines
Eye Examination in Infants, Children, and Young Adults by Pediatricians
Neurofibromatosis Type 1 in Genetic Counseling Practice: Recommendations of the National Society of Genetic Counselors
Clinical studies
Pirfenidone in Treating Young Patients With Neurofibromatosis Type 1 and Plexiform Neurofibromas
Trial to Evaluate the Safety of Lovastatin in Adults With Neurofibromatosis Type I (NF1)
Keywords
optic nerve glioma, optic pathway glioma, optic glioma, neurofibromatosis, neurofibromatosis type 1, NF-1, neurofibromatosis 1, von Recklinghausen disease, optic nerve disease, hybrid phakomatosis
