AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Background

Optic nerve glioma (also known as optic pathway glioma) is the most common primary neoplasm of the optic nerve. Along with reducing visual acuity in the affected eye, the tumor sometimes produces additional symptoms as it grows. A low-grade form of this neoplasm, benign optic glioma, occurs most often in pediatric patients. Another form, aggressive glioma, is most common in adults; it is frequently fatal, even with treatment.

Contrasted computed tomography (CT) scanning can be used to characterize local involvement of optic nerve glioma within the orbit. However, magnetic resonance imaging (MRI) better demonstrates the extent of the lesion's intracranial growth.

Many children with optic nerve glioma are also known to have neurofibromatosis type 1 (NF-1) or, in some cases, the more recently described hybrid phakomatosis.

Pathophysiology

The World Health Organization classifies optic nerve gliomas as grade I astrocytomas (pilocytic astrocytomas) because they are slow growing and tend not to metastasize. Development of optic nerve gliomas occurs in stages, from generalized hyperplasia of glial cells in the nerve to complete disorganization with loss of neural landmarks in the nerve and nerve sheath. A reactive meningeal hyperplasia may be incited, making optic nerve glioma difficult to distinguish from a perioptic meningioma. It is unclear which glial cells give rise to benign optic glioma.

From 10 to 38% of pediatric patients with optic nerve glioma have NF-1; conversely, 15-40% of children with NF-1 have optic nerve glioma. Bilateral optic nerve gliomas are almost pathognomonic for NF-1 (Listernick, 1989).

In the aggressive form of the disease, the glioma is either an anaplastic astrocytoma or a glioblastoma multiforme, arising from abnormal astrocytes. Prominent features of this neoplasm include nuclear pleomorphism, numerous mitoses, and vascular endothelial proliferation.

Frequency

United States

• Optic nerve gliomas represent 4% of orbital tumors, 4% of intracranial gliomas, and 2% of intracranial tumors. They also comprise two thirds of all primary optic nerve tumors (Hollander, 1999).
• Aggressive glioma is rare. According to Millar et al (1995), it is an unusual presentation of a more common adult disease, astrocytoma.

Mortality/Morbidity

Benign optic glioma grows relatively slowly, if at all, over extended periods. However, some lesions can progress, causing visual impairment, so ongoing follow-up has been recommended (Thiagalingam, 2004).

Twenty percent of optic gliomas that extend to the optic chiasm or beyond, into the optic radiations, demonstrate a more aggressive course.

Local surgical therapy for large lesions may cause significant morbidity, including hypothalamic dysfunction. Stereotactic radiation or gamma-knife therapy also can produce complications, including decreased visual acuity, radiation-induced optic neuritis, and ophthalmic artery vasculopathy.

Despite aggressive radiation, chemotherapeutic, or surgical treatment, aggressive glioma is an almost uniformly fatal disease.

Race

There is no distinct racial predilection to sporadic optic nerve glioma. Benign optic glioma has the same distribution as NF-1.

Sex

In pediatric patients, there is a slight female predominance, whereas in adult patients, the opposite is true (Hollander).

Age

In the pediatric population, the median patient age is 5 years, with 80% of patients presenting before age 15 (Hollander).

In adult patients, the age ranges from 22-79 years, with a mean age of 52 years (Millar).

Anatomy

The optic nerve is divided into 4 parts: (1) intraocular, (2) intraorbital, (3) intracanalicular, and (4) intracranial. Within the orbit, the nerve usually is approximately 5 mm in diameter and is surrounded by fat. The intracanalicular portion passes through the lesser wing of the sphenoid and is surrounded by a muscular cone. The cerebrospinal fluid (CSF) of the subarachnoid space surrounding the nerve is contiguous with the CSF of the intracranial compartment.

In 66% of NF-1 patients with optic nerve glioma, the growth involves the intraorbital optic nerve. In 10-20%, the tumor is confined to the orbit, with the remainder of these patients showing involvement of the intracranial compartment. In the absence of NF-1, the optic chiasm is most commonly involved, as is, less often, the intraorbital optic nerve (Kornreich, 2001). Optic nerve glioma may involve various portions of the retrobulbar visual pathway, including the optic nerve, chiasm, tracts, and radiations. Malignant lesions can invade the hypothalamus, basal ganglia, and internal capsule directly, or they may spread to the leptomeninges or subpial surfaces.

Clinical Details

In most young patients with optic glioma, the presenting symptom is painless proptosis. Optic atrophy is common, as is reduced visual acuity, although the latter may be a late symptom. A large lesion may compress the optic chiasm, causing nystagmus or other symptoms. Hypothalamic symptoms, such as changes in appetite or sleep, also may occur. Massive lesions may compress the third ventricle, resulting in obstructive hydrocephalus accompanied by headache, nausea, and vomiting.

In adult patients, bilateral vision loss is a common early finding because most lesions involve the optic chiasm.

Preferred Examination

When the diagnosis is in question, the presence of an intraconal mass can often be detected through CT scanning.

MRI, however, is the preferred method for definitive evaluation of optic nerve glioma. Both the intraorbital lesion and its intracranial extent can be effectively characterized through MRI. When evaluating the orbit, gadolinium-enhanced T1-weighted images with fat saturation can define the extent of aggressive glioma. Intracranially, MRI allows better evaluation of the optic nerve, chiasm, tracts, geniculate body, and optic radiations than does CT.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.

As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Limitations of Techniques

Although MRI may reveal even subtle lesions of the optic nerve, CT scanning can detect a subtle erosion or expansion of the optic canal. In addition, fine calcification, which may help to identify a lesion as a meningioma rather than a glioma, is visualized best through CT scanning.

DIFFERENTIALS

Section 3 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Other Problems to be Considered

Optic nerve meningioma
Lymphoma, soft tissue
Optic nerve sheath ectasia

RADIOGRAPH

Section 4 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Plain radiographs do not play a role in the evaluation of optic nerve glioma.

CT SCAN

Section 5 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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.

MRI

Section 6 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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 (Kornreich, 2001).

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.

ULTRASOUND

Section 7 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Ultrasound does not play a role in the evaluation of optic nerve glioma.

NUCLEAR MEDICINE

Section 8 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Nuclear medicine studies do not play a role in the evaluation of optic nerve glioma.

ANGIOGRAPHY

Section 9 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Angiography does not play a role in the evaluation of optic nerve glioma.

INTERVENTION

Section 10 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

At present, no radiologic intervention techniques are used to treat optic nerve glioma.

Medical/Legal Pitfalls

• Failure to diagnose early lesions correctly

Special Concerns

• Give special consideration to children with optic nerve glioma. Because these patients undergo numerous examinations, make an effort to minimize the radiation dose if CT scanning is a primary modality for following the lesion.
• Shield pregnant patients during examinations involving radiation exposure.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  Coronal noncontrast T1-weighted MRI reveals a large intraorbital mass (arrow) centered on the optic nerve.
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Media type:  MRI

Media file 2:  Coronal postgadolinium T1-weighted MRI with fat saturation (same patient as in Image 1) reveals diffuse, intense enhancement of the intraorbital mass (arrow).
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Media type:  MRI

Media file 3:  Axial postgadolinium T1-weighted MRI with fat saturation (same patient as in Images 1 and 2) reveals diffuse, intense enhancement of the intraorbital mass. The lesion is confined to the orbit.
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Media type:  MRI

Media file 4:  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.
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Media type:  MRI

Media file 5:  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.
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Media type:  MRI

Media file 6:  Axial noncontrast T1-weighted MRI in a 46-year-old man demonstrates enlargement of both optic tracts (arrowheads) and the optic chiasm (arrow).
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Media type:  MRI

Media file 7:  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.
	View Full Size Image
Media type:  MRI

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

• 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].
• Hollander MD, FitzPatrick M, O''Connor SG, et al. Optic gliomas. Radiol Clin North Am. Jan 1999;37(1):59-71, ix. [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].
• 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.
• 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].
• Messori A, Salvolini U. Hybrid phakomatosis: from initial CT observation to molecular studies. AJNR Am J Neuroradiol. Aug 2004;25(7):1297-8.
• 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].
• 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.

Article Last Updated: Feb 21, 2007