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Ventricular Anatomy Using a Brain Model
CSF Formation and Ventricular Anatomy
Subarachnoid CSF Pathway
Spinal Cord CSF Pathway
CSF Cisternal Anatomy

Ventricular Anatomy Using a Brain Model

There are two lateral ventricles. The lateral ventricles are C shaped structures (with a tail) that are deep in the cerebral hemispheres. The parts of the lateral ventricle include the anterior or frontal horn, the body, the trigone or atrium, the posterior or occipital horn and the inferior or temporal horn. Each lateral ventricle communicates with the thin single midline 3^rd ventricle by their interventricular foramen of Monro. The 3^rd ventricle is connected to the 4^th ventricle by the cerebral aqueduct of Sylvius. The 4^th ventricle communicates with the subarachnoid space by a medial aperture, the foramen of Magendie and two lateral apertures, the foramen of Luschka.

CSF Formation and Ventricular Anatomy

Most of the CSF is formed by the choroid plexus. In the lateral ventricles, the choroid plexus is a continuous structure that is found on the floor of the body and anterior trigone and the superior medial aspect of the temporal horns. The choroid plexus of the lateral ventricles travels through the foramen of Monro and is continuous with the choroid plexus found in the roof of the 3^rd ventricle. There is also choroid plexus in the roof of the 4^th ventricle.

Subarachnoid CSF Pathway

Spinal fluid exits the 4^th ventricle by the lateral apertures of Luschka and the medial aperture of Magendie. It then enters the subarachnoid space. Some of the CSF flows caudal down around the spinal cord but most of it flows around the brainstem and the cerebellar hemispheres through the tentorial notch and then up over the convexities of the cerebral hemispheres and is reabsorbed back into the venous circulation through the arachnoid villi which are arachnoid membrane evaginations that protrude mainly into the superior sagittal sinus. There are also some arachnoid villi that protrude into the transverse sinus.

Spinal Cord CSF Pathway

Some of the CSF flows down around the spinal cord in the subarachnoid space. The spinal nerve roots traverse the CSF space and CSF surrounds the nerve roots as they exit through the dura. Some of the CSF is absorbed through arachnoid villi that empty into the radicular veins. The conus medullaris of the spinal cord is usually located at the inferior aspect of the L₁ vertebral body and the lumbar and sacral spinal nerve roots form the cauda equina below this level. The CSF space around the cauda equina is the lumbar cistern. Approximately 30 ml of CSF surrounds the spinal cord with most of that volume located in the lumbar cistern. The movie demonstrates that the nerve roots in the cauda equina are moving laterally to exit the spinal canal so there is a relative lack of nerve roots in the midline where the spinal needle should enter the subarachnoid space during a lumbar puncture.

CSF Cisternal Anatomy

Cisternal spaces are enlargements of the subarachnoid space and they contain “pools” of CSF. Total CSF volume for the adult brain is approximately 150 ml with 25 ml of that total in the ventricles and 75 ml in the cisterns. The major intracranial cisterns are demonstrated in the movie including the cisterna magna, quadrageminal, pontine, interpenduncular, and suprasellar cisterns. Cisterns are important anatomical structures to identify when looking at brain scans. If they are missing or compressed then this could indicate mass effect from displaced brain tissue as seen in cerebral edema or a tumor.