CSF and Ventricular System Dr. Nimir Dr. Safaa

Objectives Describe the ventricles of brain and importance of their choroids plexus. Summarize the pathway of cerebrospinal fluid (CSF) circulation. Locate the safe sites for the lumbar puncture. Identify brain ventricles in CT scan, MRI and ventriculograms.

Ventricles: They are four fluid-filled cavities located within the brain, there are two lateral ventricles, third ventricle, and fourth ventricle. Lateral ventricles(one in each hemisphere) communicate through interventricular foramina (of Monro) with third ventricle. The third is connected to the fourth by cerebral aqueduct (of Sylvius).

Lateral Ventricles: The ventricle is C-shaped cavity divided into a body, whithin parietal lobe, anterior horn in frontal lobe, posterior in occipital lobe, and inferior in temporal lobe. The body has: Roof & lateral wall formed by corpus callosum. Floor by body of caudate nucleus & thalamus. Medial wall by septum pellucidum.

Anterior horn has: Roof & lateral wall formed by anterior part of corpus callosum. Floor by head of caudate nucleus. Medial wall by septum pellucidum. Posterior horn has: Roof & lateral wall formed by fibers of tapetum of corpus callosum. Medial wall formed superiorly by forceps major of corpus callosum & inferiorly by calcar avis of calcrine sulcus.

Inferior horn has: Roof formed by fibers of tapetum of corpus callosum & tail of caudate nucleus . Floor formed laterally by collateral eminence, produced by collateral fissure, and medially by hippocampus.

Choroid plexus of the lateral ventricle: It is a vascular plexus composed of pia mater covered with ependymal lining of the ventricular cavity. It enters the ventricle through choroid fissure between fornix & thalamus. Its function is to produce cerebrospinal fluid.

Third Ventricle: Is space between two thalami. Its anterior wall is formed by lamina terminalis. Its posterior wall is formed by epithalmus. Its roof formed by tela choroidea which is below fornix and corpus callosum. Its floor is formed by: Optic chiasma Tuber cinereum, Infundibulum Mammillary bodies.

Its choroid plexuses is formed from tela choroidea. The tela choroidea is a two-layered fold of pia mater that projects through the roof of the ventricle and is covered by ependyma. It communicates with lateral ventricles through interventricular foramina (of Monro), and it communicates fourth ventricle through cerebral aqueduct.

Fourth ventricle: It is anterior to cerebellum and posterior to pons and superior half of medulla oblongata. Its floor (Rhomboid Fossa) formed by posterior surface of pons & upper medulla. Its roof formed by superior medullary velum & inferior medullary velum.

Inferior medullary velum contains median aperture of Magendie & lateral apertures of Luschka through which CSF pass to subarachnoid space. Its choroid plexus has a T shape which formed from highly vascular tela choroidea.

Cerebrospinal fluid (CSF) is formed in ventricles by choroid plexuses. Pass from lateral ventricles to third through interventricular foramina then through cerebral aqueduct to fourth ventricle. From fourth to subarachnoid space through foramina of Luschka & Magendie

Absorption(Drainage) The main sites for the absorption of the cerebrospinal fluid are the arachnoid villi that project into the dural venous sinuses Especially the superior sagittal sinus. The arachnoid villi tend to be grouped together to form elevations known as arachnoid granulations.

Lumbar puncture: With a careful aseptic technique and under local anesthesia, Lumbar puncture (spinal tap) needle, fitted with a stylet, is passed into the vertebral canal above or below the fourth lumbar spine.

A) Pre-operative axial head CT scan demonstrating enlarged ventricles.

B) Post-operative axial head CT demonstrating decrease in the size of the lateral and third ventricles after shunt placement.