Neoplasm in the fourth ventricle was resected . [ results ] among the 20 cases total resection was in 14 and subtotal resection was in 6 . [ conclusion ] the cerebello - medullary fissure opproach can provide a panoramic view between the two laterl recesses 方法对20例第脑室内肿瘤均采取枕下正中开颅,经扁桃体下小脑延髓裂入路,显微镜下切除第脑室内肿瘤。