The cerebral aqueduct (aqueduct of the midbrain, aqueduct of Sylvius, Sylvian aqueduct, mesencephalic duct) is a small, narrow tube connecting the third and fourth ventricles of the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

. The cerebral aqueduct is a midline structure that passes through the

midbrain The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum. It is functionally associated with vision, hearing, mo ...

. It extends rostrocaudally through the entirety of the more posterior part of the

. It is surrounded by the

periaqueductal gray The periaqueductal gray (PAG), also known as the central gray, is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. PAG is also the primary control center for ...

(central gray), a layer of gray matter. Congenital stenosis of the cerebral aqueduct is a cause of congenital hydrocephalus. It is named for Franciscus Sylvius.

Anatomy

The cerebral aqueduct is roughly circular in transverse section, and measures 1-2 mm in diameter. It is 15 mm long and is commonly subdivided into a pars anterior antrum, and pars posterior.

Relations

Rostrally, it is continuous with the

third ventricle The third ventricle is one of the four connected cerebral ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and lef ...

, commencing just inferior to the

posterior commissure The posterior commissure (also known as the epithalamic commissure) is a rounded band of white fibers crossing the middle line on the dorsal aspect of the rostral end of the cerebral aqueduct. It is important in the bilateral pupillary light re ...

. Caudally, it is continuous with the

fourth ventricle The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ...

at the junction of the mesencephalon and pons. The

midbrain tegmentum The midbrain is anatomically delineated into the tectum (roof) and the tegmentum (floor). The midbrain tegmentum extends from the substantia nigra to the cerebral aqueduct in a horizontal section of the midbrain. It forms the floor of the midbra ...

is situated anteriorly to the cerebral aqueduct. The portion of the tegmentum posterior to the aqueduct is the

tectum The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum. It is functionally associated with vision, hearing, mo ...

. The superior and inferior colliculi that make up the corpora quadrigemina are situated posteriorly to it.

Development

The cerebral aqueduct, as other parts of the ventricular system of the brain, develops from the central canal of the neural tube, and it originates from the portion of the

neural tube In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, ...

that is present in the developing mesencephalon, hence the name "mesencephalic duct."

Function

The cerebral aqueduct acts as a

canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface ...

that passes through the

. It connects the

with the

so that

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

(CSF) moves between the cerebral ventricles and the canal connecting these ventricles.

Clinical significance

Aqueductal stenosis, a narrowing of the cerebral aqueduct, obstructs the flow of CSF and has been associated with non-communicating hydrocephalus. Such narrowing can be

congenital A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

, arise via

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

compression (e.g.

pinealoblastoma Pineoblastoma is a malignant tumor of the pineal gland. A pineoblastoma is a supratentorial midline primitive neuroectodermal tumor. Pineoblastoma can present at any age, but is most common in young children. They account for 0.001% of all prima ...

), or through cyclical

gliosis Gliosis is a nonspecific reactive change of glial cells in response to damage to the central nervous system (CNS). In most cases, gliosis involves the proliferation or hypertrophy of several different types of glial cells, including astrocytes ...

secondary to an initial partial obstruction.

History

The cerebral aqueduct was first named after Franciscus Sylvius.

Additional images

File:Gray710.png, Transverse section through mid-brain; number 2 indicates the cerebral aqueduct. File:Gray711.png, Transverse section of mid-brain at level of inferior colliculi. File:Gray712.png, Transverse section of mid-brain at level of superior colliculi. File:Periaqueductal_MRI.PNG, MRI section of mid-brain. File:Gray720.png, Median sagittal section of brain. File:Gray734.png, Scheme showing relations of the ventricles to the surface of the brain. File:Slide1qq.JPG, Cerebral aqueduct File:Slide7qq.JPG, Cerebral aqueduct File:Slide2HOM.JPG, Cerebral peduncle, optic chasm, cerebral aqueduct. Inferior view. Deep dissection. File:Slide3HOM.JPG, Cerebral peduncle, optic chasm, cerebral aqueduct. Inferior view. Deep dissection. File:Slide2ERV.JPG, Cerebrum. Inferior view. Deep dissection

References

External links

* {{Authority control Ventricular system