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Management of Meningiomas
File 13: CONVEXITY MENINGIOMAS

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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.
External carotid angiogram
FIG. 17.20. Convexity meningioma. Selective external carotid angiogram shows the typical hypertrophied middle meningeal artery that supplies these tumors. Angiography is no longer used because we know that this blood supply can be occluded as the dura is opened around the tumor. There is no need to do embolization.

Contents


CONVEXITY MENINGIOMAS

(Meningioma Management, File 13)

Management

Line drawing of Meningioma
FIG. 17.21. Convexity meningioma. Incision and bone flap for a meningioma centered along the coronal suture.

Convexity meningioma describes those tumors whose attachment does not occur on the dura of the skull base or does not involve the dural venous sinus or falx. The tumor may arise from any area of the dura over the convexity, but they are more common along the coronal suture and near the parasagittal region. Various classifications regarding location have been proposed (19, 42). Patients usually present with seizures, headache, or a focal neurological deficit, depending on the tumor location.

In most situations MRI gives all the information one needs. I no longer do angiography for most patients with convexity meningiomas since blood supply is known and the procedure does not add any crucial information for planning the operation. Embolization is not needed in these patients. The feeding meningeal arteries can be occluded early in the course of the operation (Fig. 17.20).

Surgery is indicated in patients with worsening neurological symptoms and in most patients under 70 who present with a seizure or with any neurological symptoms. If patients are over 70 and present with a seizure or have mild symptoms, they can be followed with scans and undergo surgery if there is evidence of definite growth. However, if there is significant edema or a history of worsening symptoms, age is not a contraindication to surgery. A number of patients are now seen in whom the tumor is found incidently and there is no edema. These patients can be followed with periodic scans, including those with large tumors. Radiation therapy is not recommended in this group.

The details of the operation have been reported by several neurosurgeons (19, 26, 41, 47, 53). The key considerations in the operation include the following.
MRI and Line Drawing of Convexity Meningioma
FIG. 17.22. Convexity meningioma. This 58-year-old woman presented with a seizure. Total removal was followed by a full recovery. (A and B) MRI axial (A) and coronal (B) T2 images show the relationship of the middle cerebral artery to the convexity meningioma projecting into the sylvian fissure. The edema in the adjacent brain areas is also seen. (C) During tumor removal the surgeon must remember that the middle cerebral artery branches may be adherent to the media] capsule.

  1. The head is positioned so that the center of the tumor is uppermost, the same position as described for parasagittal tumors or for tumors close to the midline.
  2. The incision and bone flap must be large enough to allow for excision of a good margin of dura around the tumor attachments (FIG. 17.21).
  3. The meningeal arteries are occluded as they are exposed.
  4. These tumors can be removed intact by placing gentle traction on the dural attachment and working circumferentially around the tumor to divide the attachments to the cortex. However, if the surface of the tumor cannot be easily visualized without placing significant retraction on the cortex, internal decompression of the tumor is done and the capsule is reflected into the area of decompression.
  5. In a situation where the tumor arises over the frontal temporal junction and grows into the sylvian fissure, the medial capsule and the dural attachment may extend down onto the lateral floor of the anterior fossa and anterior wall of the middle fossa, and the medial capsule of the tumor can be attached to branches of the middle cerebral artery (Fig. 17.22).

Results

In this series there were 66 patients, 44 women and 22 men, ranging in age from 31 to 82 years, with 18 over 70 years of age (Table 17.12). All were symptomatic except for one with an enlarging tumor on follow-up scan. All but one patient had total removal of their tumors. The one exception was an 80-year-old man with a large tumor growing into the sylvia,n fissure at the frontal-temporal junction. A small fragment of tumor was left adherent to the middle cerebral artery.
TABLE 17.12 Convexity Meningiomas
aRemoval bOutcome Complications Recurrence
T 65 Good 66 Temporary
deficit
3 1
RST 1 Fair 0
ST 0 Poor 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.
Postoperative complications included three with a temporary increase in hemiparesis and sensory loss, one with difficulty controlling seizures, one wound infection, and one with deep venous thrombosis. All patients had a good result. There has been evidence of only one recurrence. This was in a patient with an atypical meningioma with regrowth 5 years after resection. The recurrence was removed and there has been no further recurrence over 9 years. The low rate of recurrence has been documented in other publications (I 1, 44).

How long a patient should remain on anticonvulsant medication after these operations has not been established. If there is a history of preoperative seizure, long-term medication may be required. If there has been no history of seizure, we usually taper off the medication 2-3 months after operation.

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