Microsurgery in Skull Base Meningiomas : Mainly Focusing on Clinoidal Meningioma(<SPECIAL ISSUE>Skull Base Surgery in the Radiosurgery Era)

Abstract

Clinoidal meningioma is one of the most challenging skull base tumors for neurosurgeons. When the tumor encases the internal carotid artery, middle cerebral artery, or the anterior cerebral artery and their perforators, total removal of the tumor is particularly difficult. Nevertheless, the achievement of total removal at the first operation is especially important, because adhesion of the tumor to important vessels and nerves becomes more severe when it recurs. In this article, the authors describe some surgical techniques to achieve total removal with preservation of the encased arteries. At the initial stage of the surgery, devascularization of the tumor is performed to reduce the blood loss. Thereafter, we start debulking the tumor and dissecting the encased arteries. In order to dissect the arteries encased by the tumor safely, the following techniques are recommended: 1) split the tumor above the encased arteries and the perforators, 2) dissect the divided tumors from the arteries one by one, 3) cut the intervening fibers around the perforators after aspiration of the soft components of the tumor. When numerous draining veins are observed around the large tumor in angiography, those veins can be observed as red veins in the operation. It is important to find out the correct part of the vein to cut without damaging the venous drainage of the normal surrounding brain. And also, more attention should be paid in these cases to achieve complete hemostasis during the tumor removal.