Navigating the Brain’s Waterways: Understanding the Ventricular System
Introduction
These are cavities within the substance of the brain. They are derived from the lumen of the neural tube and the spinal cord. It is separated by the central canal in the spinal cord.
Topographical/Gross Anatomy
The lateral ventricle is c-shaped and located with the cerebral hemispheres. It communicates via the intraventricular foramen with the 3rd ventricle. The 3rd ventricle is the midline slit-like cavity. Its lateral walls consist of the thalamus and hypothalamus. Caudally, the 3rd ventricle becomes continuous with the cerebral aqueduct. The cerebral aqueduct extends throughout the midbrain linking the 3rd and 4th ventricles. The 4th ventricle is located between the brainstem (i.e. the pons and medulla) and the cerebellum. It has 2 lateral apertures and a medial aperture which communicates with the subarachnoid space.
The Ventricles: Lateral Ventricles
Ventricle of the cerebrum located within the hemispheres. C-shaped.
Parts:
- Anterior horn
- Central part
- Posterior horn
- Inferior horn
Anterior Horn
Extends forwards into the frontal lobe from intraventricular foramen.
Boundaries:
- Anteriorly: Genu of the corpus callosum
- Roof: Limbic part of hook of corpus callosum
- Floor:
- Lateral part – rounded head of caudate nucleus
- Medial part – rostrum of corpus callosum
- Medial:
Central Part
Extends from intraventricular foramen to splenium of corpus callosum.
Boundaries:
- Medial wall: Posterior part of septum pellucidum
- Roof: Inferior surface of corpus callosum
- Floor (from lateral to medial):
- Caudate nucleus
- Thalamostriate vein
- Stria terminalis
Posterior Horn
Curves backwards and medially into the occipital lobe.
Boundaries:
- Roof and lateral wall: Fibres of tapetum of corpus callosum
- Medial wall:
- Upper elevation – forceps major and the bulb
- Lower elevation – calcarine sulcus
Inferior Horn
Traverses the temporal lobe after curving around the posterior end of the thalamus.
Boundaries:
- Roof: Tapetum of corpus callosum
- Floor:
- Medially – hippocampus
- Laterally – medial eminence
3rd Ventricle
Often referred to as the ventricle of the diencephalon. Is a medial cleft located between the two thalami and communicates posteriorly with the 4th ventricle and cranially with the lateral ventricle.
Boundaries:
- Roof: Layers of ependymal
- Floor: Structures which belong to hypothalamus (optic chiasma, infundibulum, tubercinguli), Mammillary bodies
- Anteriorly: Lamina terminalis, Column of fornix, Anterior commissure
- Posteriorly: Pineal recess, Suprapineal recess
- Laterally:
- Medial wall of thalamus (upper)
- Hypothalamus (lower)
4th Ventricle
Located ventral to the cerebellum and dorsal to the pons and cranial half of the medulla. Continuous with the central canal below and the 3rd ventricle above through cerebral aqueduct.
Boundaries:
- Roof: Formed by superior medullary velum
- Floor: Diamond in shape. Bounded above by superior peduncle and below by inferior cerebellar peduncle. Formed by back of pons above and open part of medulla below. Has elevations known as medial eminence in the middle. Laterally has depression in the pontine area known as superior fovea and depression in the medulla (inferior fovea).
Clinical Correlates
- Serves as site of CSF production
- Blockage of CSF leads to hydrocephalus
- Ependymal cell tumor could occur in the ventricles
- Collection of blood or pus during infection
