Cerebral aqueduct

The cerebral aqueduct (aque ductus mesencephali, mesencephalic duct, sylvian aqueduct or aqueduct of Sylvius) is a narrow 15 mm conduit for cerebrospinal fluid (CSF) that connects the third ventricle to the fourth ventricle of the ventricular system of the brain. It is located in the midbrain dorsal to the pons and ventral to the cerebellum. The cerebral aqueduct is surrounded by an enclosing area of gray matter called the periaqueductal gray, or central gray. It was first named after Franciscus Sylvius.