The term brainstem tegmentum refers to the region of the brainstem located ventral to the cerebral aqueduct and the fourth ventricle. It consists of the medullary tegmentum, the pontine tegmentum, and the midbrain tegmentum. The brainstem tegmentum contains the cranial nerve nuclei, the reticular formation of the brainstem, and a variety of ascending and descending tracts ( Pritchard-1999 ). Some authors subdivide the brainstem longitudinally into the brainstem tegmentum, the anterior part of the brainstem, the ventricular system of the brainstem, and the Tectum (Schiebler) ( Schiebler-1999 ).