Anatomical aspects for surgery within the floor of the IVth ventricle.

: Successful removal of brainstem lesions is among other factors dependent on a safe surgical approach into the brainstem avoiding functional morbidity of superficially located nervous structures. Most midline pontine and pontomedullary lesions can be reached via a transvermian approach through the rhomboid fossa. This review describes the anatomical basis for the pericollicular paramedian surgical approaches into the rhomboid fossa with special emphasis on the microscopic anatomy.