The cerebral aqueduct, or "aqueduct of Sylvius," connects the third and fourth ventricles providing a conduit for cerebrospinal fluid (CSF) to flow inside the brain. This aqueduct is located in the midbrain and forms part of the CSF ventricular system, prompting About.com to describe the structure as a canal between the ventricles.
The cerebral aqueduct is situated in the mesencephalon and plays a crucial role in the storage, transport, and recycling of the CSF, according to Wikipedia. This part of the ventricular system within the brain develops from the central canal of the neural tube and ensures the steady flow of CSF between the third and fourth ventricles in the midbrain.
Sometimes, the cerebral aqueduct becomes the site of serious medical problems. One of these problems is obstructive hydrocephalus. It's "obstructive" because, as the National Institutes of Health explains, the condition is caused by aqueductal stenosis, or a narrowing of the cerebral aqueduct that obstructs the flow of CSF between the ventricles. The condition is inherited and some estimates report one to two of every 1,000 babies are born with hydrocephalus. The most common way to treat this obstruction is by inserting a shunt to drain off surplus CSF, usually into the abdominal cavity.