Surgical approach to the fourth ventricle cavity through the cerebellomedullary fissure.

Lesions of the fourth ventricle represent a challenge to neurosurgeons because of severe deficits that occur following injury to the delicate structures in the ventricle wall and floor. The conventional approach to the fourth ventricle is by splitting the vermis on the suboccipital surface of the cerebellum. In the last 9 years, a series of 21 patients in our clinic underwent microsurgical tumor resection by the unilateral transcerebellomedullary fissure approach. The patients had various pathologies including hemangioblastoma, epidermoid tumor, medulloblastoma, ependymoma, low grade astrocytoma, choroid plexus carcinoma, choroid plexus papilloma, adenocarcinoma in the pons, and cavernoma in the medulla. Total removal was achieved in all but three cases. One death occurred 2 months after surgery due to pulmonary complication. In the follow-up period of 2 months to 5 years, the preoperative symptoms disappeared in all cases except one with a brainstem lesion. By a unilateral transcerebellomedullary fissure approach, it is possible to provide sufficient operative space from aqueduct to obex without splitting the vermis. This approach needs meticulous dissection of the fissure and preservation of the posterior inferior cerebellar artery and its branches.