Speakers

SURGICAL MANAGEMENT OF MESENCEPHALIC BRAINSTEM TUMORS
1109 15:20-15:30
AASNS & WANS Joint Seminar/305
The anatomy of the brainstem is one of the most challenging of the Central Nervous System. The mesencephalic area can harbor different tumors, among them cavernomas, a benign and curable disease. Anatomy plays a very important role to avoid postoperative morbidity. The surgical approach must be tailored for every case, trying to incorporate the anatomical concept of “safe entry zone”. Skull base osteotomies to improve the access may be needed for antero-lateral (peduncular) tumors. In this presentation we deal with the anterior, posterior and lateral approaches to mesencephalic brainstem tumors. The subtemporal approach or a cranio-zygomatic approach can lead to the antero-lateral aspects. The mesencephalic median sulcus, the safe entry zone of the lateral mesencephalon, can be reached through parmedian supracerebellar infratentorial approaches. The dorsal mesencephalon can be reached through a transtentorial -suboccipital. Timing is another aspect to be taking into account, trying to avoid early (riskier due to the situation of the patient / higher probability of subtotal removal) and delayed surgery (risk of gliotic tissue around the tumor with increased neurological postoperative morbidity). The surgery of brainstem tumors must be done in the context of a perfect knowledge of the anatomical neurovascular structures. Timing for surgery is also crucial. Some skull base approaches can be helpful to enter the safe entry zones, along with intraoperative neurophysiological monitoring.

MANAGEMENT OF MECKEL'S CAVE LESIONS
1108 13:10-13:20
Skull Base/304A
The petrous apex s a very complex anatomical region located at the petrous pyramid. The neurovascular relations are of paramount importance (petrous carotid artery, cavernous sinus, greater petrosal superficial nerve, trigeminal ganglion). Many approaches have been devised to reach this area. In this paper the experience approaching the petrous apex by means of a temporal or fronto-temporal craniotomy with the addition of zygomatic osteotomy is presented and compare with endoscopic alternative approaches. Regarding microsurgical excision, although many publication point out the need for orbito-zygomatic osteotomy, in the author experience the simple zygomatic osteotomy is enough. An extradural dissection is done, indentifying the GPSN and petrous trajectory of the petrous carotid artery. The anterior petrous apex is approached. This route also allows for the removal of interdurally placed neoplasms (typically trigeminal neuromas) by means of interdural approach. The posterior fossa can be also reached (transpetrous approach). Lesions at the bony petrous apex like cholesterol granuloma and epidermoid cysts can be removed through microsurgical and endoscopic approaches. Tumors at the petrous-sphenoidal junction (chondrosarcoma) can be excised and also trigeminal schwannoma can be removed, even being followed to the posterior fossa. For dumbell schwannoma the autors prefer transcranial approaches. If the interdural approach is difficult (epidural bleeding, etc), an intradural approach can be done satisfactory. To follow the dumbbell tumors to the posterior fossa, the petrous superior sinus must be cut. Intraoperative monitoring is of paramount importance in this surgery (VI nerve monitoring is usually very helpful).

1. Anterior petrosal approach 2. Brain stem cavernoma
1109 16:20-16:30
Video Presentation/304B