Tumors of the Fourth Ventricle and Cerebellum in Adults

Abstract

The posterior fossa can harbor a diverse pathological spectrum of lesions. The incidence of these lesions varies considerably with age. Intraaxial tumors in this region can originate from the fourth ventricle, cerebellum and/or brain stem. Although the vast majority of intra-axial posterior fossa tumors in adults are metastatic in origin, other tumors and tumor like lesions may be encountered in this region, especially in young adults. The management strategy depends on the nature and localization of the lesion and preoperative radiological diagnosis plays a very important role in choosing this strategy. When surgery is indicated, cerebellar tumors can be approached with a median suboccipital craniectomy, unilateral posterior fossa craniectomy or lateral suboccipital retromastoid approaches. The fourth ventricle tumors are also approached with a posterior median craniotomy/craniectomy. After dural opening, the fourth ventricle is exposed through the telovelotonsillar fissure by cutting the tela choroidea or with a midline approach with vermian splitting. The exposure of fourth ventricle tumors by splitting of the vermis was first described by Dandy, who indicated that this can be performed without serious complications. However, cerebellar mutism, as well as other neurological sequelae. As an alternative technique to avoid vermian splitting, Ya§argil described the median inferior suboccipital approach along the tonsillouveal sulcus to expose fourth ventricle lesions. Matsushima et al. reported the use of cerebellomedullary fissure for a similar approach.