Last Updated: October 21, 2018
Lesions of the fourth ventricle are covered by the cerebellar vermis and may be exposed through either of two operative corridors: The telovelar and transvermian routes. The transvermian approach which involves transecting the inferior vermis is typically used for large lesions that occupy the rostral fourth ventricle and do not extend into the lateral recesses. The disadvantages of this approach are that the exposure is limited to midline lesions and the vermis must be divided. Vermian split syndrome manifests with nystagmus, gait disturbance, oscillation of the head and neck, truncal ataxia, and disturbance in equilibrium. In addition, pediatric patients may suffer from cerebellar mutism.