Third ventricle

Last revised by Travis Fahrenhorst-Jones on 20 Jul 2022

The third ventricle is one of the four CSF-filled cavities that together comprise the ventricular system.

The third ventricle is a median cleft between the two thalami, which make up the superior aspect of the lateral walls. The thalami are separated from the hypothalamus (anteriorly) and subthalamus (posteriorly) by the hypothalamic sulcus. The size of the third ventricle varies from 2 to 10 mm and enlarges with age 4. A third ventricle size of more than 10 mm is considered dilated 5.

The anterior wall of the third ventricle is formed from superior to inferior by the columns of the fornix, the anterior commissure, and the lamina terminalis 4.

Posteriorly, it is bounded from superior to inferior by the habenular commissure, the pineal gland, and the posterior commissure.

The roof is formed by the choroidal fissure and the bodies of the fornix 4.

The floor is bounded from anterior to posterior by the optic chiasm (posterior aspect), the infundibulum of the pituitary gland, the tuber cinereum, and the mammillary bodies.

There are two small anterior recesses and two small posterior recesses:

The third ventricle contains choroid plexus along its roof along the tela choroidea continuous with the choroid plexus from the lateral ventricles.

It communicates with the:

In some patients, the two thalami meet forming the interthalamic adhesion and when casts are made of the ventricular system, a hole is seen through the third ventricle.

The infundibular recess can vary in its invagination into the infundibulum, most commonly extending the entire length. While less commonly 50% or <50% of the length of the infundibular stalk can also occur 3.

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Cases and figures

  • Figure 1: ventricular system
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  • Figure 2: IVH outlining the recesses of the third ventricle
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  • Figure 3: ventricles superimposed on lateral brain
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  • Figure 4: coronal brain through 3rd ventricle
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  • Figure 5: pineal region anatomy
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