ABSTRACT
Brainstem4 The brainstem represents the infratentorial portion of the central nervous system (CNS), consisting of the mesencephalon (midbrain), pons, and medulla. It lies anterior to the cerebellum and is connected to it via the superior, middle, and inferior cerebellar peduncles, containing the fourth ventricle, cerebral aqueduct, and the central canal. Through the fourth ventricle, the cerebrospinal fluid (CSF) drains into the subarachnoid space and eventually into the systemic venous circulation. This part of the CNS is connected to the 3rd through the 12th cranial nerves and contains the associated motor and sensory nuclei. The central core of the brainstem contains deeply seated reticular nuclei that regulate sleep and control respiratory and cardiovascular centers.
