Optic Nerve Sheath Meningioma

By Paul T. Finger, MD

Graphic of how an eye can look with a posterior orbital tumor.
Graphic of how an eye can look with a posterior orbital tumor.

Orbital and optic nerve meningioma can extend from the brain into the orbit (behind the eye) and push the eye forward causing a bulging of the eye called proptosis. Though rare, when they occur, they are a significant cause of vision loss.

Symptoms

Patient with orbital meningioma typically have proptosis (bulging eye). Optic nerve compression can cause optociliary shunt vessels to form, as well as loss of vision. Depending on the location, size and degree of optic nerve involvement; patients can develop monocular and/or junctional defect is the patients field of vision.

Diagnosis

Opto-ciliary shunt vessels resulting from optic nerve compression
Opto-ciliary shunt vessels resulting from optic nerve compression

Patients usually present in their 40s and may have neurofibromatosis type 2. In making this diagnosis, one should look for the triad of vision loss, optic atrophy and abnormal vessels on the optic nerve. The nerve head can appear raised. Enlarged blood vessels are called “optociliary shunt vessels” and indicated that the meningioma has disrupted the natural circulation through the optic nerve to the retina and choroid. Angiography of the optic nerve head will clearly demonstrate the abnormal blood vessels. Magnetic resonance imaging (MRI), ultrasonography and computed tomographic (CT) imaging have been used to evaluate the orbital tumor and measure the optic nerve sheath diameter. CT is particularly helpful for imaging calcium within the tumor.

 

Computed tomography (CT) shows that the eye is pushed forward by this optic nerve sheath meningioma. Notice that the tumor is relatively bright (radio-dense). Imaging of the brain can determine if the meningioma extends into the brain.

In the images above, note that computed tomography of this optic nerve sheath meningioma. C demonstrates the calcific density of the left optic nerve. An x-ray film shows the linear density (seen on the right side of the film crossing the inferior orbital rim) which corresponds to the optic nerve sheath meningioma seen above.

Coronal "C-scan" ultrasound can be used to compare optic nerve diameters in a case of optic nerve sheath meningioma
Coronal “C-scan” ultrasound can be used to compare optic nerve diameters in a case of optic nerve sheath meningioma

Treatment Plan

Orbital meningioma is typically a slow-growing tumor. Once diagnosed, meningioma can be observed for growth prior to considering intervention. Treatment is indicated when there is a risk of spread to the central nervous system (in primary optic nerve sheath meningioma), documented progressive vision loss, or for rapid growth.

Computed tomography of the optic nerve sheath meningioma. Note the almost calcific density of the left optic nerve. An x-ray film shows the linear density (seen on the right side of the film crossing the inferior orbital rim) which corresponds to the optic nerve sheath meningioma seen above.

Though microsurgical resections have been tried (in an effort to spare the optic nerve), most eventually fail. The goal of local resection should be complete removal of the meningioma. This usually involves removal of the involved optic nerve. If complete surgical removal is not possible or in special circumstances, radiation therapy is commonly employed.

Biopsy:

Indications for biopsy include: atypical tumors, aggressive disease, acute vision loss and when a pathology diagnosis is requested. Certain inflammatory tumors can have a similar appearance to orbital meningiomas. However, biopsy carries risk for vision loss.

Treatment:

Orbital meningioma is typically a slow-growing tumor. One must consider patient age, rate of tumor growth and risk for loss of vision. That said, once diagnosed slow or non-growing meningiomas can be observed for further growth or stabilization prior to considering intervention. In general, treatment is indicated when there is a risk of spread to the central nervous system (in primary optic nerve sheath meningioma), documented progressive vision loss, or for rapid growth.

Treatment alternatives are tailored to the clinical situation. For example, if vision is lost, the tumor is growing toward the central nervous system and is resectable; it is removed. If complete surgical removal is not possible or in special circumstances,  microsurgical resection or external beam radiation therapy can be considered. These decisions are complex and best made with your neuro-ophthalmologist, neurologist and orbital surgeon.

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Optic Nerve Melanocytoma

By Paul T. Finger, MD

Description

Note the dark tumor located next to and within the optic nerve. The edges have a feathered appearance (arrow).
Note the dark tumor located next to and within the optic nerve. The edges have a feathered appearance (arrow).

Optic nerve melanocytoma is typically a benign tumor made up of melanocytes and melanin. They can grow, but rarely transform into a malignancy. However, local growth can harm adjacent tissues.

Symptoms

Optic nerve melanocytoma does not usually produce symptoms or grow. If they slowly grow, optic nerve melanocytoma can produce afferent pupillary defects (30%), subretinal fluid (10%), and an enlarged blind spot (75%).

For example, if the tumor is next to the optic nerve, growth can compress the nerve and cause loss of vision (e.g. nerve fiber layer defects). Growth can also cause compressive vascular problems like central retinal vein occlusion. Lastly, growth also causes the tumor to exceed its blood supply. In these cases, necrotic areas form inside the tumor. Necrosis can (in turn) cause intraocular and rarely orbital inflammation.

Diagnosis

Most optic nerve melanocytomas are small, black, and do not grow. A medium-sized juxtapapillary melanocytoma
Most optic nerve melanocytomas are small, black, and do not grow.
A medium-sized juxtapapillary melanocytoma
A small juxtapapillary melanocytoma (note the small feathered edge).
A small juxtapapillary melanocytoma (note the small feathered edge).

Unlike choroidal melanoma, optic nerve melanocytomas are black, commonly extend onto the surface of the optic nerve and invade the nerve fiber layer (feathered edge).

Treatments

Patients with optic nerve melanocytoma should have a visual field test, as well as a photograph of the optic nerve and tumor. These examinations can serve as a baseline for future comparison. Patients with optic nerve melanocytoma should be periodically examined for evidence of growth, loss of visual field and optic nerve compression.

Unfortunately, there are no current treatments to prevent or stop optic nerve melanocytoma growth. Patients are examined every 6 to 12 months with dilated ophthalmoscopy and visual field examinations as to counsel patients about the risk of vision loss, treat compression-related vasculopathy and monitor for the rare occurrence of malignant transformation.

Additional info

Though rare, tumor growth can lead to radiation or enucleation (removal of the eye). 

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Choroidal Melanoma Affecting the Optic Nerve

By Paul T. Finger, MD

Description

Choroidal melanoma can grow near, touch and even cover the optic nerve. Like other choroidal melanomas, they can exhibit orange pigment on its surface, subretinal fluid (localized retinal detachment), and thickness. The choroidal melanoma in the next photograph exhibits all three findings.

Symptoms

Juxtapapillary choroidal melanoma is typically near the central macular retina and may cause symptoms. Unlike most patients with choroidal melanoma, when the optic nerve is affected patients will have complaints of decreased vision, visual field defects, flashing lights or floaters (spots). However, most choroidal melanomas are found on routine eye examination with dilated ophthalmoscopy.

Diagnosis

Choroidal melanoma that affects the optic nerve must be differentiated from optic nerve melanocytoma. The eye care specialist will examine the tumor for evidence of orange pigment (lipofuscin, melanolipofuscin), thickness (as measured by ultrasound), for leakage (as measured by photography with angiography), and with optical coherence tomography (OCT).

Unlike optic nerve melanocytoma, malignant choroidal melanoma does not typically spread-out along the nerve fiber layer and are lighter in color. In addition, melanocytoma-OCT findings can be particularly helpful showing tumor cell invasion of the overlying retina and vitreous. In either case, it can be difficult to determine the diagnosis of very small tumors. In these cases, the tumor can be closely watched “followed” for evidence of growth, then a biopsy may need be performed. Dr. Finger has found that melanomas that completely encircle the optic disc (circumpapillary) are likely to cause an afferent pupillary defect.

Treatments

Choroidal melanoma that encircles or covers the optic nerve are particulary difficult to treat with eye-sparing plaque radiation therapy. This is because the optic nerve widens as it leaves the eye into the orbit. In addition, it becomes encased in the optic nerve sheath. Dr. Fingers’ 3D ultrasound studies showed that the nerve nearly triples in diameter behind the eye. Therefore, if a plaque is perfectly placed on the back of the eye, it can only reach to 1.5 mm from the optic disc (effectively missing the rest of the uncovered melanoma. This is why, many patients with melanomas touching or surrounding the optic disc were treated by removal (enucleation) of the affected eye.

Now with 12-years follow up, 94% of patients with choroidal melanoma do not have to lose their eye. For those tough to peripapillary, juxtapapillary and even circumpapillary melaoma, Dr. Finger invented 8-mm slotted plaques. The slot accomodated the entire optic nerve sheath into the plaque, thus allowing the plaque radiation to completely cover and surround the cancer. Fingers’ Slotted Plaques have been able to control more than 98% of these melanomas, has been able to spare some vision (with subsequent intensive anti-VEGF therapy) and allow patients to keep their eye. The patient must be counseled that they are at risk for impaired vision in the irradiated eye.

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Patient Stories

"Very well treated by Dr. Finger. He explained everything I needed to know about my issue with detail and attention, putting me at ease and giving me confidence to handle this problem for the rest of my life.”
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