The right and left lateral ventricles are structures within the brain that contain cerebrospinal fluid, a clear, watery fluid that provides cushioning for the brain while also helping to circulate nutrients and remove waste.

Along with the structures known as the third ventricle and the fourth ventricle, the lateral ventricles are part of the body's ventricular system. The ventricular system acts as a continuation of the central canal of the spinal cord, a similar structure that contains cerebrospinal fluid and runs the length of the neck and trunk.

The separate sections of the ventricular system are connected through small holes known as foramina. The lateral and third ventricles connect through the right and left interventricular foramina, while the third and fourth ventricles connect through a foramen known as the cerebral aqueduct. Other foramina that connect to specific ventricles exist but are not considered part of the ventricular system.

The volume of the lateral ventricles, and similar structures within the brain, can be measured through a CT scan. The scan allows doctors to measure not only the size of the ventricles but also the density of the cerebrospinal fluid that they contain. This information can be used to diagnose potential problems within the brain, including hydrocephalus, an abnormal accumulation of fluid in the ventricles. Hydrocephalus can lead to progressive skull enlargement.