CEREBRAL AQUEDUCT

The cerebral aqueduct (of Sylvius) is the midbrain (mesencephalic) portion of the cerebral ventricular lumen, and connects the much broader ventricles rostral and caudal to the midbrain: the third ventricle of the forebrain and the fourth ventricle in the hindbrain. The cerebrospinal fluid, most of which is produced in the lateral (the first two) ventricles of the forebrain, flows through the narrow aqueduct to reach the fourth ventricle, from where it exits through the median (of Magendie) and lateral (of Luschka) ventricular recesses to fill the extracerebral subarachnoid space, from whence it is absorbed into the blood stream.