Lateral ventricle

Last revised by Yaïr Glick on 2 Dec 2023

The lateral ventricles are paired CSF-filled spaces in the cerebrum and part of the ventricular system of the brain. They are larger than the third or fourth ventricles but can be asymmetrical. Each has five divisions, including three horns that project into the lobe after which they are named:

  • anterior/frontal horn

  • inferior/temporal horn

  • body

  • trigone/atrium

  • posterior/occipital horn

    • often asymmetrical 3

    • may be absent, poorly developed 3

CSF is produced in the choroid plexus located along the lateral walls of the lateral ventricles related to the choroid fissure and exits along the interventricular foramen (of Monro) into the third ventricle. The central part of the lateral ventricle is called the cella media. The posterior confluence of the occipital and temporal horns is called the trigone or atrium of the ventricles.

The volume of the lateral ventricles is known to increase with age due to cerebral involution. They may also be enlarged in a number of neurological conditions (e.g. schizophrenia and bipolar disorder) or pathologically enlarged as part of hydrocephalus. ​The Evans index is the ratio of the maximal width of the frontal horns to the maximal internal skull diameter. An Evans index of >0.30 represents ventriculomegaly, however the normal ratio can vary depending on imaging angle, plane, patient sex and age 4.

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