Space
Fourth ventricle
Where ventricular CSF reaches the subarachnoid space
High-yield
One median aperture, Magendie, opens toward the cisterna magna. Two lateral apertures, Luschka, open from the lateral recesses into the subarachnoid space beside the brainstem.
Overview
The fourth ventricle lies behind the pons and upper medulla and in front of the cerebellum. Its diamond-shaped floor is the rhomboid fossa, whose surface landmarks reflect nearby brainstem structures. The cavity narrows upward into the cerebral aqueduct and downward toward the central canal. Three apertures provide the normal ventricular outlets to the subarachnoid space.
Reference facts
- Boundaries
- Rhomboid floor formed by dorsal pons and open medulla; roof includes the superior medullary velum above and inferior medullary velum with tela choroidea below, beneath the cerebellum. Superior and inferior cerebellar peduncles contribute to its margins
- Contents
- CSF and choroid plexus attached to the tela choroidea. The floor overlies brainstem tissue; its facial colliculus reflects the abducens nucleus and looping facial fibers, while other landmarks include the hypoglossal and vagal trigones
- Communications
- Cerebral aqueduct rostrally; central canal caudally; median and paired lateral apertures into the subarachnoid space
Clinical correlation
Obstruction of the fourth-ventricle outlets can cause hydrocephalus, often enlarging all four ventricles if upstream connections remain open. The pattern differs when the fourth ventricle is also isolated at the aqueduct. Its relationship to brainstem nuclei explains why nearby masses can affect eye movements, swallowing or other cranial-nerve functions.
Frequently asked questions
What are the boundaries of the fourth ventricle?
Rhomboid floor formed by dorsal pons and open medulla; roof includes the superior medullary velum above and inferior medullary velum with tela choroidea below, beneath the cerebellum. Superior and inferior cerebellar peduncles contribute to its margins.
What does the fourth ventricle contain?
CSF and choroid plexus attached to the tela choroidea. The floor overlies brainstem tissue; its facial colliculus reflects the abducens nucleus and looping facial fibers, while other landmarks include the hypoglossal and vagal trigones.
What does the fourth ventricle communicate with?
Cerebral aqueduct rostrally; central canal caudally; median and paired lateral apertures into the subarachnoid space.