Space
Third ventricle
The midline ventricular channel between diencephalic structures
High-yield
Two interventricular foramina lead into this midline cavity; one cerebral aqueduct leads onward to the fourth ventricle. Recesses extend toward the optic, infundibular and pineal regions.
Overview
The third ventricle lies between the thalami superiorly and hypothalamic regions inferiorly. CSF enters from the lateral ventricles and passes toward the midbrain aqueduct. Choroid plexus projects from its roof. The nearby internal cerebral veins lie in the roof's vascular membranes rather than free within the ventricular cavity.
Reference facts
- Boundaries
- Thalamic and hypothalamic lateral walls; roof membranes beneath the fornix; lamina terminalis anteriorly; optic-chiasmatic, infundibular, tuberal and mammillary regions in the floor, continuing posteriorly toward the midbrain.
- Contents
- CSF and roof-associated choroid plexus. An interthalamic adhesion often crosses the cavity, but may be absent as a normal variant.
- Communications
- Receives the lateral ventricles through paired interventricular foramina and connects posteriorly to the fourth ventricle through the cerebral aqueduct.
Clinical correlation
A mass can obstruct ventricular drainage and cause hydrocephalus. Some mobile or strategically placed lesions produce intermittent obstruction with posture-related headache or loss of consciousness, but many ventricular masses present differently.
Frequently asked questions
What are the boundaries of the third ventricle?
Thalamic and hypothalamic lateral walls; roof membranes beneath the fornix; lamina terminalis anteriorly; optic-chiasmatic, infundibular, tuberal and mammillary regions in the floor, continuing posteriorly toward the midbrain.
What does the third ventricle contain?
CSF and roof-associated choroid plexus. An interthalamic adhesion often crosses the cavity, but may be absent as a normal variant.
What does the third ventricle communicate with?
Receives the lateral ventricles through paired interventricular foramina and connects posteriorly to the fourth ventricle through the cerebral aqueduct.