There are several areas in the lateral ventricle: • the frontal horn, which is bounded by the caudate nucleus, Corpus callosum and septum pellucidum • the body of the lateral ventricle is bounded by the caudate nucleus / thalamus, corpus callosum and fornix • the atrium: this is the focal point of the occipital and temporal horns • the occipital horn • the temporal horn
The two lateral ventricles (right, left) communicate with each other via the third ventricle.
Ventricles are interconnected, fluid-filled cavities found in the center of the forebrain and the brainstem.
There is a total of four ventricles that make up the brain’s ventricular system. The largest of these cavities or spaces are the lateral ventricles(1).
Anatomy of the Lateral Ventricles
The brain possesses two lateral ventricles, one each for the left and right cerebral hemispheres.
The lateral ventricles resemble a pair of hollow, C-shaped structures. Each lateral ventricle can hold an estimated 7ml to 10ml of fluid(2).
The lateral ventricles are made up of a central part or body, an atrium or chamber, and three extensions referred to as horns(3). These extensions are:
- The anterior or frontal horn
- The posterior or occipital horn
- The inferior (lower) or temporal horn
Body of the Lateral Ventricles
The body of the lateral ventricles is formed by its surrounding structures and organs. The roof of the lateral ventricle is made up of the body or trunk of the corpus callosum, a bundle of nerves between the two brain hemispheres(4).
Meanwhile, the part of the floor of the lateral ventricle’s body is formed by the thalamus(5). The ventricles’ walls are formed by the septum pellucidum and the body of the fornix.
The septum pellucidum is a thin membrane separating the cerebral hemispheres, while the body of the fornix is a white brain matter structure connected to the corpus callosum.
The frontal horn is a projection located in front of the interventricular foramen or the foramina of Monro(6).
The foramina of Monro is a short pathway connecting the lateral ventricles with the third ventricle and allowing the two structures to communicate.
The lateral ventricles’ frontal horn is a triangle-shaped extension. The boundaries of the frontal horn are(7):
- The anterior (front) part of the body of the corpus callosum
- The head of the caudate nucleus (a deep brain structure near the thalamus, which is the information hub of the brain)
- The septum pellucidum
The occipital horn is connected to the body and temporal horn via the atrium, a triangular cavity.
The occipital horn curves towards the back and away from the atrium. Moreover, the occipital horn extends into the occipital lobe(8).
The occipital horn’s roof and wall are formed by different structures, including the tapetum(9). The tapetum is a sheet-like mass of intersecting fibers in the corpus callosum’s splenium(10).
The temporal horn is the biggest and longest protuberance of the lateral ventricles. The temporal horn extends towards the front from the atrium and stops at the amygdala(11).
A cross-section of the lateral ventricles showed that the temporal horn is a narrow space surrounded by the following(12):
- On its top and side: tapetum, tail of caudate lobe, stria terminalis, and amygdaloid body
- On its bottom or floor: hippocampus
Structural Variations of the Lateral Ventricles
Knowledge of the anatomic variations of the lateral ventricles and the ventricular system as a whole is necessary to avoid misinterpreting the structures as medical disorders.
Coarctation means the fusion or apposition of two ventricular walls. This fusion causes a partial or complete elimination of the lumen (open spaces)(13).
Coarctation of the occipital horns is a common occurrence, with an incidence rate of 21.3%(14). In comparison, the unilateral or bilateral coarctation of the frontal horn only has a reported incidence rate of 0.38% to 6%.
Ventricular coarctation may be mistaken for periventricular leukomalacia or similar appearing subependymal cysts(15). However, ventricular coarctation is accepted as benign anatomical variations
Size Asymmetry Between Lateral Ventricles
The size of the lateral ventricles may sometimes be asymmetrical. Findings showed that size asymmetry between the lateral ventricles is present in 5% to 12% of healthy people(16).
The shape of the lateral ventricles exhibits marked differences. Researchers noted that the occipital horn is the most inconsistent part of the lateral ventricle(17).
The occipital horn may vary in length, and in some cases, it may even be completely absent(18). The temporal horn, particularly its front tip, also varies in shape, though it is not as inconsistent as the occipital horn.
In some cases, the lateral ventricles may become abnormally enlarged. This condition is referred to as ventriculomegaly(19).
Lateral ventriculomegaly is a disorder more commonly observed among fetuses during gestation(20). Findings showed that 73% of ventriculomegaly cases were mild, with only 4.3% of cases deemed severe.
Magnetic resonance (MR) imaging was used to examine the lateral ventricles of the fetuses. The researchers noted that MR imaging during the gestation period can also help in the early diagnosis of central nervous system anomalies(21).
• Harnsberger HR, Osborn AG, Ross JS, Moore KR, Salzman KL, Carrasco CR, Halmiton BE, Davidson HC, Wiggins RH. Diagnostic and Surgical Imaging Anatomy: Brain, Head and Neck, Spine. 3rd ed. Salt Lake City, Utah. Amirsys. 2007. • Bourjat P, Veillon F. Imagerie radiologique tête et cou. Paris, Vigot. 1995. • Gouazé A, Baumann JA, Dhem A. Sobota. Atlas d’Anatomie humaine. Tome 3. Système nerveux central, système nerveux autonome, organe des sens et peau, vaisseaux et nerfs périphériques. 1er éd. Paris, Maloine. 1977. • Kahle W, Cabrol C. Anatomie. Tome 3: Système nerveux et organe des sens. 1er éd. Paris, Flammarion. 1979.