Third ventricle floor

The floor of the third ventricle is located medial to the uncus and anterior perforated substance and above the midbrain. From anterior to posterior, the floor includes the lower margin of the optic chiasm, the pituitary stalk surrounded by the tuber cinereum, mamillary bodies, and the midbrain.

The floor of the third ventricle extends anteriorly from the optic chiasm to the sylvian aqueduct posteriorly. The anterior wall of the third ventricle is formed from superior to inferiorly by the columns of the fornix, the foramina of Monro, the anterior commissure, lamina terminalis, optic recess, and optic chiasm.

The floor of the third ventricle is formed by hypothalamic structures and this can be opened surgically between the mammillary body and the pituitary gland in a procedure called an endoscopic third ventriculostomy.