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Management of Meningiomas
File 17: CEREBELLOPONTINE ANGLE MENINGIOMA
MRI of Meningioma
FIG. 17.30. Cerebellopontine angle meningioma. This 41-year-old woman noted increased numbness in the left side of her face and decreased hearing in her left ear. A radical subtotal removal was done, with tumor left encasing the fourth nerve and going into the anterior wall of the internal auditory canal. (A-D) MRI axial TI images after gadolinium show the typical appearance of a meningioma, with the flat surface against the petrous bone and the dural "tails." This tumor is arising anterior to the left internal auditory meatus. It may extend into the internal auditory meatus, as seen here.

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by ROBERT G. OJEMANN, M.D.

Congress of Neurological Surgeons Honored Guest Presentation
Originally Published Clinical Neurosurgery, Volume 40, Chapter 17, Pages 321-383, 1992
Used with permission of the Congress of Neurological Surgeons.

HTML Editor: Stephen B. Tatter, M.D., Ph.D.


Disclaimer: The information and reference materials contained herein are intended solely to provide background information. They were written for an audience of physicians. They are in no way intended to constitute medical advise. For medical advise a physician must, of course, be consulted.

Contents


CEREBELLOPONTINE ANGLE MENINGIOMAS

(Meningioma Management, File 17)

Management

These meningiomas may arise from any area of the dura on the postelior surface of the petrous bone. At operation four general categories of tumor are found, depending on where they arise and their relationship to the seventh and eighth nerve complex:

  1. Anterior to the internal auditory meatus, displacing the seventh and eighth nerves posteriorly and inferiorly (Fig. 17.30).
  2. Between the internal auditory meatus and the jugular foramen, displacing the seventh and eighth nerves superiorly.
  3. Superior to the internal auditory meatus, displacing the seventh and eighth nerves anteriorly in the large tumors (Fig. 17.31).
  4. Surrounding the internal auditory meatus, with the seventh and eighth nerves engulfed in the tumor.
MRI of Meningioma
FIG. 17.31. Cerebellopontine angle meningioma. This 40-year-old woman had progressively decreased hearing in her left ear and discomfort around her ear and the side of her head. Total removal of the tumor was done using a combined posterior fossa and transmeatal approach. There was normal recovery. (A-D) MRI axial TI images after gadolinium show a large meningioma arising posterior to the left internal auditory meatus.
The MRI scan usually defines those tumors that arise posterior to the internal auditory meatus but will not distinguish the first three categories. The diagnosis of meningioma is indicated by the flat surface of the tumor against the petrous bone and the durat "tail" extending from the tumor.

In the past I often utilized angiography when a cerebellopontine angle meningioma was suspected. However, for most of these meningiomas it is now not necessary, because the MRI usually gives all the information needed and in most patients the blood supply comes primarily through the dural attachment. Embolization has not been a consideration.

In patients with mild or minimal symptoms, an initial period of clinical evaluation and repeat scans may be indicated to determine whether there are progressive symptoms and an enlarging tumor. This is especially true in the elderly.

The indications for operation are a worsening neurological deficit due to brainstem compression or cranial nerve compression. In a few patients headache or the continued presence of a stable deficit such as diplopia or hearing loss may be the indication. In this series two patients were asymptomatic. One had documented enlargement on follow-up scans and the other was concerned about the presence of the tumor. Radiation therapy has been used when there is regrowth after subtotal or radical subtotal removal and with small tumors which start to enlarge in older patients who are being observed.

I use the supine position with the ipsilateral shoulder slightly elevated and the head turned to the opposite side. The details have been described (47) (see Chap. 24). This approach has worked well for visualization of the important anatomical structures, tumor removal, comfort of the operator, and avoidance of problems with air embolism or hypotension. Guthrie et al. (26) described a similar approach. Other surgeons have used the sitting position and achieved good results (58, 65, 79).

The key considerations in the operation include:

  1. Exposure of the tumor as described in Chap. 23.
  2. Interruption of the blood supply along the dural attachments.
  3. Internal decompression combined with careful dissection of the tumor capsule from the brainstem and cranial nerves.

Results

There were 57 patients with cerebellopontine angle meningiomas, 37 women and 20 men, ranging in age from 38 to 89 years, with 10 over 70 years of age (Table 17.16). In the 42 patients listed in Table 17.16, Anterior, the tumor arose anterior to the internal auditory meatus in 27 and anterior-inferior in 10 and grew diffusely in five. The extent of the tumor removal is recorded in Table 17.16. In only 14 patients could I be sure of a total removal but in another 10 a radical subtotal removal was done. On follow-up, 34 of the 42 patients had a good result, three had a fair result because of postoperative disability, four had poor results because of severe preoperative neurological disabilities that did not significantly improve, and there was one postoperative death. This occurred
TABLE 17.16 Cerebellopontine Angle Meningiomas
aRemoval bOutcome Complications Recurrence
Anterior Posterior Anterior Posterior Anterior Posterior
T 14 13 Good 34 15 Permanent
deficit
3 0 5 Anterior
RST 10 1 Fair 3 0 Cerebellar
infarction
1 0
ST 18 1 Poor 4 (4) 0 Meningitis 1 0 0 Posterior
Death 1 0 CSF leak 1 0
aT, total removal
RST, radical subtotal removal
ST, subtotal removal
bGood, free of major neurological deficit and able to return to previous activity level
Fair, independent but not able to return to full activity because of new neurological
deficit or significant preoperative deficit that did not fully recover
Poor, dependent.
in an 89-year-old man who had been well until he started to develop worsening ataxia. CT showed a 4-cm tumor with hydrocephalus. A shunt was placed, with improvement, but several months later symptoms of brainstem compression worsened. A subtotal removal was done but the patient died of a cardiopulmonary complication.

None of the patients with radical subtotal removal has shown recurrence and all have been followed by scans. Most of the patients with subtotal removal had large tumors (>3 cm). Three were growing anteriorly into the middle fossa. After subtotal removal, 15 of 18 had follow-up scans, which showed no growth in eight, slight growth in five (three of whom have been given radiation therapy and two of whom are being observed after showing no further growth on subsequent scans), and moderate growth in two of the disabled patients, where nothing further has been done.

Postoperative complications included permanent increased ataxia in three, one of whom had to have a cerebellar infarction removed, one patient with wound infection and meningitis, and one with a cerebrospinal fluid leak requiring repair. Several patients had temporary increases in ataxia, incoordination, or swallowing problems which improved. Four patients had a shunt for hydrocephalus at some time in their course.

Of the 15 patients with meningiomas arising posterior to the internal auditory meatus, 13 had a total removal (Table 17.16). One had a radical subtotal and one a subtotal removal because of involvement of the lower cranial nerves. All had a good result. There were no postoperative neurological complications and no recurrences.

Yasargil et al. (79) reported that 27 of 30 patients had a good result and in 27 the tumor was "radically excised." Sekhar and Jannetta (65) reported total removal in 14 of 22 patients, with no operative mortality and a good outcome in 16. Samii and Ammirati (58) reported total removal of all 24 tumors located posterior to the internal auditory meatus, with a good outcome for 22 patients. Of 32 patients with tumors anterior to the internal auditory meatus, 29 had the tumors totally removed and 28 had a good outcome.

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