Fourth Ventricl

e Dr. Muhammad Rafique

Anatomy, DIMC,

Objectives Know location of fourth ventricleRecognize the boundaries of fourth

ventricleDiscuss the features of lateral boundaries Describe the features of roof and floorDiscuss the circulation of CSFKnow abnormal condition related to

circulation of CSF

Gross Anatomy Fourth ventricle is the cavity

of hind brain. It is present behind the pons and upper half of medulla oblongata and infront of cerebellum. The fourth ventricle is a tent shaped cavity filled with cerebrospinal fluid. It is lined with ependyma and continuous above with cerebral aqueduct and below with central canal of medulla oblongata

Boundaries of Fourth Ventricle

The boundaries of fourth ventricle are

Two lateral boundaries: Right & Left

Roof with Tela Choroidea

Floor or Rhomboid Fossa

Lateral Boundaries

Each lateral boundary consists of two parts:

Inferior Part:

Formed by Inferior Cerebellar Peduncle

Superior Part:

Formed by Superior cerebellar peduncle

Roof or Posterior WallThe inferior part of the roof is

formed by the inferior medullary velum, which formed by the thin sheet of ventricular ependyma along with the Pia Mater.

This part of roof contains a large aperture in the mid line the median aperture or foramen of Magendie which connects the ventricular with sub-arachnoid space

Roof or Posterior WallThe roof of fourth

ventricle extends toward the cerebellum.

The superior part is formed by medial borders of two superior cerebellar peduncles and connecting sheet of white matter called the superior medullary velum.

Tela Choroidea The Tela Choroidea of the

fourth ventricle is a double layer of pia mater that lies in the interval between the cerebellum and the lower part of the roof of ventricle. In this region the blood vessels of the tela choroidea form rich vascular fringe that projects through the lower part of the roof of the fourth ventricle to form the choroid plexus

Tela ChoroideaIn the lower part of roof of fourth

ventricle the cavity of ventricle extends laterally over the surface of inferior cerebellar peduncle to form the lateral recess of the ventricle. The lateral recess on each side opens into sub-arachnoid space by a lateral aperture or Foramen Luschka. Cavity of 4th ventricle communicates with sub-arachnoid space through a single median opening a & two lateral apertures. These openings permit the flow of CSF fro ventricular system to sub-arachnoid Space

Floor or Rhomboid Fossa The floor is formed by the

posterior surface of the pons the posterior surface of upper half of the medulla oblongata. The floor is divided into symmetrical halves by the median sulcus. On each side of sulcus there is an elevation the medial eminence which bounded laterally another sulcus, the sulcu Limitan.

Floor or Rhomboid FossaLateral to the sulcus limitans

there is an area the vestibular area which overlies the vestibular nuclei.

Facial colliculus is a slight swelling at the inferior end of the medial eminence that is produced by the fibers from the motor nucleus of the facial looping over the abducens nucleus.

Floor or Rhomboid FossaThe nerve fibers, the

stria medullaris, derived from the arcuate nuclei emerge from the median sulcus and pass laterally over the medial eminence and the vestibular area and enter the inferior cerebellar peduncle to reach the cerebellum

Floor or Rhomboid Fossa

Inferior to the stria medullaris the features recognized in the floor of the fourth ventricle are:

Most medial is the Hypoglossal Triangle which indicates the position of Hypoglossal Nucleus.

Lateral to this is the Vagal Triangle overlies the dorsal motor nucleus of vagus nerve

Floor or Rhomboid Fossa

Area Postrema ia a narrow area between the vagal triangle and the lateral margin of the ventricle

Choroid Plexus of Fourth Ventricle The function of

choroid plexus of the fourth ventricle is to produced the CSF. The choroid plexus consists of ependymal cells, Pia mater and blood capillaries. The ependymal cells are responsible for the secretion of CSF

Hydrocephalus It is can be defined as the

abnormal increase in volume of CSF with in skull. This can be occurred due to increase formation of CSF or decrease drainage of CSF, this can occur in condition like the blockage of foramina in the roof of fourth ventricle

This may congenital or acquire