Optic Nerve Sheath Meningioma Treatment & Management

Updated: May 18, 2016
  • Author: Mitchell V Gossman, MD; Chief Editor: Hampton Roy, Sr, MD  more...
  • Print
Treatment

Medical Care

Many believe that patients with optic nerve sheath meningioma (ONSM) can be observed if there is no evidence of intracranial extension and if there is mild or no vision loss or, in some cases, stable degrees of vision loss. [13]

Radiologic findings help diagnose most cases; therefore, biopsy is unnecessary. Biopsy should be reserved for only rare cases with ambiguous neuroimaging findings because the effects on vision can be catastrophic.

Radiotherapy

Treatment with primary radiation or radiation following surgical removal has been associated with a better chance of visual improvement. [14, 15, 16]

Conventional radiation therapy is beneficial for patients with recurrent (or incompletely resected) benign meningiomas, and it is recommended for patients with aggressive and malignant meningiomas. Patients with meningiomas are good candidates for radiotherapy because the tumors are extra-axial and are visualized easily on CT scan or MRI. Stereotactic radiation and interstitial brachytherapy are useful in some refractory or recurrent meningiomas.

In the largest, most comprehensive review of patients with meningiomas from 1962-1980 by Mirimanoff et al, only 80 patients out of 225 had residual tumor after debulking. [17] This study suggests that the recurrence rate for patients with full resection of tumor is about 10%, whereas patients with subtotal resection had a recurrence rate of 55% at 10 years and 91% at 15 years.

In another study by Barbaro et al, patients with subtotal resection of benign meningiomas were divided into 2 groups; one group received postoperative radiotherapy, and the other group was only observed. [18] The rate of tumor progression was 60% for the latter group and 32% for the former group. In addition, the time to progression was twice as long for patients who had received radiotherapy. The improved survival rate was associated with higher radiation doses; 93% survival rate for patients having received 52 Gy versus 65% for patients treated with smaller doses.

In a study by Goldsmith et al, the 5-year survival rate was 58% for patients with malignant meningiomas who had received additional radiotherapy. This rate was significantly higher than the survival rate of patients who had only surgery. In this group, only 3.6% had serious complications (eg, blindness, brain necrosis). In another review by Glaholm et al, the 10-year survival rate was 46% for patients who had received radiotherapy alone for treatment of unresectable meningiomas. [19]

One proposed protocol to minimize adverse effects is to deliver fractionated external radiation of 1.8 Gy per day for a total of 54 Gy. For superficial tumors, radiation with a 4-6 MV accelerator or a Cobalt 60 machine is preferred because these parameters spare skin lesions and allow a rapid build-up of radiation dose.

Radiosurgery can be delivered with either a gamma knife or a modified linear accelerator. The gamma knife can deliver multiple small fields with relative ease; therefore, it conforms well to uneven masses. The use of linear accelerators for radiosurgery and stereotactic radiotherapy has resulted in an improved outcome from radiation. In a series of 56 skull base meningiomas by Black, 95% of them were controlled (ie, showed no growth) over a 4-year period. [20]

Chemotherapy

Chemotherapy is reserved for patients with unresectable, recurrent, or previously irradiated meningiomas. Combination treatment with 5-fluroouracil, folate, and levamisole, or a combination of intra-arterial cisplatin with intravenous doxorubicin, may be beneficial. Other proposed combinations include Adriamycin and dacarbazine or ifosfamide and mesna. Adriamycin is an antibiotic that causes DNA damage. Dacarbazine (DTIC) is an alkalizing agent that inhibits DNA synthesis for a total of 1 year, if the tumor responds, or indefinitely until a response occurs.

In a pilot study with mifepristone by Greenberg et al, a marginal response was seen in a small group of patients (6 out of 24 patients). [21] Another study by Grunberg et al confirmed benefit for a majority of 14 patients. [22]

Interferon alpha is the most frequently advocated immunotherapy and is generally well tolerated. It has been shown to have a growth inhibitory effect in vitro, and isolated reports have indicated a stabilizing response in unresectable benign meningiomas.

Next:

Surgical Care

The management scheme below has been proposed.

In the absence of visual impairment, follow up with visual function testing, including pupil testing, color vision testing, and perimetry, every 6-12 months and obtain an MRI every 1-2 years.

If visual acuity or the visual field deteriorates, it may be beneficial to treat the patient with radiation to the orbit.

If the eye is blind and the tumor is confined to the orbit, observe the patient. (In some cases, if the eye is completely blind, some advocate surgically resecting the ONSM; the globe sometimes can be left behind.)

If the eye is blind and intracranial extension is present, excise the tumor and the nerve. Possible complications of surgery include visual impairment, postoperative bleeding, and cerebrospinal fluid leakage.

Preoperative evaluation of patients with anterior basal meningiomas includes a careful visual testing and a complete neuro-ophthalmological evaluation. Endocrine testing is important, as pituitary insufficiency has been reported to occur in 22% of patients with anterior skull base meningiomas. MRI angiography may be helpful in establishing the relationship of the tumor to its vascular supply. Three-dimensional scanning is becoming increasingly popular because it can be taken into the operating room and linked to the operative instruments. Surgery remains the mainstay of meningioma management.

For any skull base surgery, the procedure can be divided into 3 steps, as follows:

  • The first step consists of providing wide exposure of the involved area. Avoid brain retraction, and interrupt the blood supply to the tumor early in the procedure to reduce intraoperative blood loss. Blood supply to the tuberculum sella is typically from posterior ethmoidal arteries with possible additional blood supply from the ipsilateral anterior cerebral artery and the anterior communicating artery. These tumors tend to displace the optic chiasm posteriorly and the optic nerves laterally and superiorly. Removal of the posterior portion of the tumor usually is relatively easy, as the posterior elements are easy to locate and usually are spared from tumor invasion.

  • The second step of the surgery consists of debulking the central portion of the tumor after dissecting its thin arachnoidal membrane capsule. Remove the involved dura and the involved bony structures. It is important to assume that the tumor is present in all areas of hyperostosis.

  • The third step is reconstructive. To minimize the risk of infection and spinal fluid leakage, separate the intracranial contents from the paranasal sinuses, the mastoid air cells, and the airway structures. A unilateral approach may be used for tuberculum sella meningiomas, including a supraorbital osteotomy, or, alternatively, make a bicoronal incision to allow access to a large pericranial flap. Once the bone flap is removed, the frontal dura and the periorbital area can be visualized. Detaching the tumor from the skull is the first step to devascularize the tumor. Complete excision usually is achieved in 97% of cases of meningiomas of the convexity. Recurrence is strongly associated with the degree of surgical debulking. Only 30% of patients with skull base meningiomas had full resection.

Previous
Next:

Consultations

In cases of optic nerve sheath meningioma (ONSM), a team approach involving ophthalmologists, neurologists, neurosurgeons, radiation therapists, and radiologists is most beneficial.

Previous