Ventricles of the brain
Ventriculi encephali
Also known as: ventricular system, cerebral ventricles
Four interconnected CSF-filled cavities within the brain (two lateral ventricles, the third and fourth ventricles) lined by ependyma, containing the choroid plexus, and continuous with the central canal of the spinal cord and, through three apertures, with the subarachnoid space.
Overview
The ventricles are the persistent lumen of the neural tube, expanded in the brain. Each cerebral hemisphere contains a lateral ventricle. Each lateral ventricle opens through an interventricular foramen (of Monro) into the midline slit-like third ventricle of the diencephalon. This drains through the narrow cerebral aqueduct (of Sylvius) in the midbrain into the diamond-shaped fourth ventricle, between the pons and medulla in front and the cerebellum behind. The fourth ventricle opens into the subarachnoid space through the median aperture (of Magendie) and two lateral apertures (of Luschka), and continues below as the central canal of the medulla and spinal cord.
All the ventricles are lined by ciliated ependymal cells, and each contains choroid plexus, which secretes most of the CSF:
• in the lateral ventricles: body, atrium and temporal horn, but not the frontal or occipital horns;
• in the roof of the third ventricle;
• in the roof of the fourth ventricle.
The total ventricular volume in a healthy adult is only ≈20–25 mL. CSF flows from the lateral ventricles to the fourth ventricle and out into the subarachnoid space, so a block at any narrow point dilates every ventricle upstream. The pattern of dilatation on imaging therefore localises obstructive hydrocephalus.
- Location
Within the cerebral hemispheres (lateral), diencephalon (third), midbrain (aqueduct) and hindbrain (fourth).
Parts & subdivisions
- C-shaped cavity of each hemisphere with frontal, occipital and temporal horns.
- Interventricular foramina (of Monro)Paired openings between the fornix and thalamus connecting each lateral ventricle with the third ventricle.
- Midline cavity between the thalami.
- Narrow channel through the midbrain.
- Between the pons/medulla and the cerebellum.
- Median and lateral aperturesMagendie (median, 1) and Luschka (lateral, 2): exits from the fourth ventricle to the subarachnoid space.
- Central canalContinuation through the closed medulla and spinal cord; often partly obliterated in adults.
Anatomy
- Development
The lumen of the neural tube: telencephalic vesicles → lateral ventricles; diencephalon → third ventricle; mesencephalon → aqueduct; rhombencephalon → fourth ventricle; caudal tube → central canal.
Function
- House the choroid plexus, which secretes CSF
- Conduct CSF from its site of production to the subarachnoid space
- Their fluid contributes to buoyancy and chemical homeostasis of the brain
Clinical significance
Localising obstruction from ventricular size
• Dilated lateral and third ventricles with a normal fourth ventricle point to aqueductal stenosis.
• Dilatation of one lateral ventricle points to a block at one foramen of Monro.
• Dilatation of all four ventricles suggests outflow obstruction from the fourth ventricle or a communicating hydrocephalus.
• Enlarged ventricles with enlarged sulci and normal pressure suggest atrophy (ex vacuo).
External ventricular drain
In acute hydrocephalus or for ICP monitoring, a catheter is passed through a burr hole at Kocher's point (≈2.5–3 cm lateral to the midline at the mid-pupillary line, ≈1 cm anterior to the coronal suture) into the frontal horn of the lateral ventricle.
Mnemonics
Fourth ventricle apertures
"Magendie = Median; Luschka = Lateral."
Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.