General Characteristics and Topography
During embryogenesis, the cavities of the brain vesicles develop into a system of interconnected spaces: the lateral ventricles, the third ventricle, the cerebral aqueduct, and the fourth ventricle. This entire system contains cerebrospinal fluid and connects with the central canal of the spinal cord.
The lateral ventricles are divided into the left (ventriculus lateralis sinister) and right (ventriculus lateralis dexter) ventricles. Anatomically, each is subdivided into several regions topographically corresponding to specific cerebral lobes. A lateral ventricle consists of a central part and three horns extending from it: the anterior, posterior, and inferior horns.
Anterior Horn and Central Part
The anterior (frontal) horn — cornu frontale (anterius) — lies within the frontal lobe. On coronal section, its cavity is triangular, with a medially convex outline.
The walls of the anterior horn are formed by:
- Superior and anterior walls: Formed by the radiations of the corpus callosum and the genu of the corpus callosum.
- Lateral wall: Formed by the head of the caudate nucleus.
- Medial wall: A thin sheet of the septum pellucidum (lamina septi pellucidi). The right and left laminae form the septum pellucidum proper (septum pellucidum), enclosing a slit-like cavity (cavum septi pellucidi) visible when the corpus callosum is removed.
In the posterior part of the medial wall (between the anterior column of the fornix and the thalamus) lies the interventricular foramen (foramen interventriculare). Through this foramen, the lateral ventricle drains CSF into the third ventricle (ventriculus tertius).
The central part — pars centralis — projects over the parietal lobe and is the longest segment. Its medial boundary is the body of the fornix (corpus fornicis), its floor is formed by the superior surface of the thalamus, and its superior and lateral boundaries are formed by the fibers of the corpus callosum. Posteriorly, this part continues into the posterior horn, and inferiorly it descends into the inferior horn.
Posterior and Inferior Horns
The posterior (occipital) horn — cornu occipitale (posterius) — is located in the occipital lobe. It is a narrow cavity, 1.2 to 2.0 cm long, triangular in coronal section. The posterior horn has three walls:
- Superior (dorsal) wall: The narrowest portion.
- Lateral wall: Convex in shape.
- Medial wall: Concave, featuring important anatomical landmarks: the bulb of the posterior horn (bulbus cornu occipitalis), formed by corpus callosum fibers, and the calcar avis (calcar avis), which corresponds to the deep calcarine sulcus of the hemisphere.
Note: The fibers of the corpus callosum forming the roof and lateral wall of the posterior horn are referred to as the tapetum.
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The inferior (temporal) horn — cornu temporale (inferius) — lies within the temporal lobe, shifted toward its medial surface. It is 3–4 cm long, curving anteriorly, inferiorly, and medially. It ends blindly anteriorly (short of the temporal pole), where the amygdaloid body (corpus amygdaloideum) lies adjacent to the uncus.
Walls of the inferior horn:
- Lateral and superior walls: Formed by fibers of the corpus callosum (tapetum).
- Inferior wall: Partially includes the collateral trigone (trigonum collaterale).
- Medial wall: Formed by the hippocampus.
Choroid Plexus and Ependyma
A crucial structure of the central part and inferior horn is the choroid plexus of the lateral ventricle — plexus choroideus ventriculi lateralis. It enters the cavity from the interventricular foramen, contributes to the formation of the medial wall, and extends into the inferior horn. In the region of the collateral trigone, it forms a notable enlargement known as the glomus choroideum (glomus choroideum). The plexus is attached to the fimbria of the hippocampus via the taenia fornicis (tenia fornicis).
Additionally, embryonic remnants persist on the ventricular walls:
- Lamina affixa (lamina affixa): A remnant of the telencephalic wall on the superior surface of the thalamus. Medially, it transitions into the taenia choroidea (tenia choroidea).
- Stria terminalis (stria terminalis): Runs lateral to the lamina affixa, precisely along the boundary between the thalamus and the caudate nucleus. Its fibers connect the amygdaloid body with hypothalamic nuclei and the septum pellucidum.