Contents

• Introduction to the therapy of Meningiomas
• General Considerations in Management of Meningiomas
  • Surgery of Meningiomas
  • Radiation Therapy of Meningiomas
  • Observation of Meningiomas
• Summary of Dr. Ojemann's Meningioma Series
  • OLFACTORY GROOVE MENINGIOMA (File 2)
  • TUBERCULUM SELLAE MENINGIOMA (File 3)
  • MEDIAL SPHENOID WING MENINGIOMA (CLINOIDAL MENINGIOMA , File 4)
  • MIDDLE RIDGE SPHENOID WING MENINGIOMA (File 5)
  • HYPEROSTOSING SPHENOID WING MENINGIOMA (File 6)
  • OPTIC SHEATH MENINGIOMA (File 7)
  • FLOOR OF FRONTAL FOSSA MENINGIOMA (File 8)
  • MIDDLE FOSSA MENINGIOMA (File 9)
  • CAVERNOUS SINUS MENINGIOMA (File 10)
  • PARASAGITTAL MENINGIOMA (File 11)
  • FALX MENINGIOMA (File 12)
  • CONVEXITY MENINGIOMA (File 13)
  • INTRAVENTRICULAR MENINGIOMA (File 14)
  • CLIVUS AND PETROCLIVAL MENINGIOMA (File 15)
  • TENTORIAL MENINGIOMA (File 16)
  • CEREBELLOPONTINE ANGLE MENINGIOMA (File 17)
  • CEREBELLAR CONVEXITY MENINGIOMA (File 18)
  • FORAMEN MAGNUM MENINGIOMA (File 19)
  • SPINAL MENINGIOMA (File 20)
  • MALIGNANT MENINGIOMAS (File 21)
• MENINGIOMA REFERENCES (File 22)

INTRODUCTION

The management of a patient with a meningioma begins with careful evaluation of the history and clinical findings. The physician needs to have a clear understanding of the symptoms and how they are affecting the patient's life. The potential impact of other medical problems is also assessed.

For many patients with a meningioma the only radiographic study needed is magnetic resonance imaging (MRI). If information is needed about bone detail, computed tomography (CT) is done. Angiography is indicated in those patients in whom embolization may be a consideration or when more information about the arterial supply or venous drainage is neededto plan the operation than can be gained from MRI or magnetic resonance angiography.

The treatment options of surgery, radiation therapy, a combination of the two, or observation with periodic scans and examinations are then evaluated. In the future, chemotherapy may be added to the options. It is important to know what the patient's expectations are from the treatment program and to carefully weigh the short- and long-term benefits and risks. In many patients an operation is clearly indicated because of increasing disability, radiographic documentation of a surgically treatable tumor, and an assessment that this treatment can be done with an acceptable risk. However, in some patients the management decision can be difficult because of minimal or nonprogressive symptoms, the indolent natural history of some meningiomas, the risks involved with treatment because of location or pathological anatomy, the development of new radiosurgery treatments the long-term results of which are still unknown, or the accidental finding of the tumor (51).

GENERAL CONSIDERATIONS IN MANAGEMENT

Surgery

Many of the surgical principles used in the treatment of meningiomas were described in the classic two-volume work published by Cushing and Eisenhardt (14). The modern management of meningiomas has been summarized in two books, Meningiomas edited by Al-Mefty and Meningiomas and Their Surgical Management edited by Schmidek, published in 1991.

The objective of the operation is total removal of the meningioma including the dural attachment and bone that is involved with the tumor. The completeness of the surgical removal is the single most important prognostic factor. However, this goal must always be tempered by surgical judgement, recognizing that the first priority is to try to preserve or improve neurological function. For patients in whom total removal of the tumor carries significant risk of morbidity, it is better to leave some tumor and plan to observe the patient. In some patients the tumor may remain stable indefinitely. In others reoperation at a future date or radiation therapy is indicated.

The key considerations in tumor removal include:

1. Careful positioning of the patient and a well planned incision to give adequate exposure.
2. Early interruption of the blood supply to the tumor.
3. Internal decompression of the tumor using the cavitron, cautery loops, and/or bipolar coagulation.
4. Careful dissection of the tumor capsule, gradually displacing it into the area of decompression, dividing vascular and arachnoid attachments as they are encountered, and minimizing retraction on the surrounding brain tissue.
5. Removal of involved dura and bone when possible.
6. Reconstruction of dural defects, when indicated, with a free graft of pericranial tissue or fascia.

Most patients are given steroids for at least 48 hours before operation and longer if there is significant brain edema. Postoperatively, the steroids are tapered off over 5 days or longer, depending on the degree of cerebral edema and the patient's condition. For most supratentorial operations administration of an anticonvulsant medication is started. Intravenous antibiotics are given before operation and for 24 hours after the procedure. If the head of the patient is to be elevated, a central venous line is placed. After induction of anesthesia and insertion of a catheter in the bladder, 10-20 mg of furosemide are given and 100 g of mannitol are administered intravenously during the exposure.

Radiation Therapy

Radiation therapy has been shown to arrest the growth of some meningiomas (25, 33, 71, 72). The indications for its use have included residual tumor left at operation, recurrence, tumors that could not be treated surgically, and malignant histology.

External-beam radiation therapy has been effective if a dose of 5000-5500 cGy is given in daily fractions of 180-200 cGY delivered over 5-6 weeks (25). The complication rate is low, but particular care must be taken with treatment near the optic nerves and brainstem.

Radiosurgery using the "Co gamma unit has also been effective (33, 72). A single treatment dose delivered to the margin of the tumor ranges from 15 to 18 Gy, depending on the proximity of the cranial nerves and brain. The optic nerves and chiasm are considered the most radiosensitive and the dose to these structures is kept below 9 Gy. The incidence of complications has been low.

The linear accelerator has also been used for the radiosurgery treatment of meningiomas (71). A dose to the tumor margins of 1500 rad is thought to be adequate for tumor control. The number of patients treated has been relatively small but the complication rate appears to be low. Experience with proton-beam irradiation has been limited but arrest of growth of meningiomas has been reported (71).

Observation

Not every patient with a meningioma needs an operation. In some patients, periodic clinical evaluation and MRI is an appropriate course to follow. The indications for observation include asymptomatic patients with little or no edema in the adjacent brain areas, patients with mild or minimal symptoms or those with a long history, older patients with a seizure or very slowly progressing symptoms, patients in whom treatment carries a significant risk, and patients who make the decision after being presented with the treatment options.

SUMMARY OF SERIES

This chapter discusses the management of patients with meningiomas based on personal experience with 373 patients operated upon over a period of 17 years (1975-1992) and a review of the literature. Some of these patients have been included in previous publications (46-55). There were 268 females and 105 males. The ages ranged from 16 to 91 years. Age by itself was not a primary factor in deciding about surgery. If the patients had good neurological function prior to the onset of symptoms from their tumors and their medical status was satisfactory, operation was considered. There were 70 patients 70 years of age or older in this surgical series. In addition to the operated patients, who are reviewed in detail, I also refer to other patients who have been followed without treatment or who have been given radiation therapy as a primary treatment.

The review starts in 1975 because at that point CT had become available for the evaluation of these patients and microsurgical techniques had been developed and refined. Each tumor location is considered separately and includes meningiomas with benign and atypical pathology. Malignant meningiomas are discussed separately because of the marked difference in clinical behavior. Patients with multiple meningiomas have been included in the category of the symptomatic lesion. The indications for recommending specific treatment options are reviewed for each meningioma category, but those outlined in the section on General Considerations in Management which apply to all tumors are not repeated unless there is a specific point to be made. Within each tumor category a table shows the extent of tumor removal, outcome, complications, and recurrence. A number in parentheses in the outcome category indicates that the patient is in that category because of a preoperative neurological deficit that did not recover enough to improve the outcome category. If a patient had more than one operation the outcome status is given for the last operation.

The terms used to record the extent of tumor removal are as follows: total (T), removal of all visible tumor; radical subtotal (RST), small fragments of tumor are left adherent to important structures; and subtotal (ST), extensive removal but a portion of the capsule is left. The terms used to designate the outcome are as follows: good (G), free of major neurological deficit and able to return to previous level of activity; fair (F), independent but not able to return to full activity because of new or preoperative neurological deficit that did not fully recover; and poor (P), dependent, with major neurological deficit.

The operative mortality in this series was 0.5% (two of 373). For 337 (90%) patients there was a good outcome. There were 14 poor outcomes, nine of these being due to preoperative neurological disabilities. There were 19 fair outcomes, and 10 of those were due to preoperative disabilities. The factors that have been important in the good long-term outcomes in this series include detailed clinical and radiological evaluations, attention to preoperative medical problems, especially in the elderly, careful consideration of the treatment options, adherence to the key considerations in surgical management, and the use of radical subtotal removal and subtotal removal in some tumors where there is marked adherence to important structures.

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