Habenular commissure

The habenular commissure lies in the superior wall of the base of the pineal stalk. It contains efferent neurons from the habenular nuclei crossing–between right and left sides–across the midline.

Anatomy of the habenular commissure can be best understood in context of knowing some details about the habenular nucleus and the pineal stalk.

Habenular nucleus is part of the epithalamus. It is situated posterior and medial to the thalamus and receives afferents (stria medullaris thalami) from the amygdala in the temporal lobe. Efferents of the habenular nucleus may cross the midline to reach its counterpart (habenular nucleus) on the other side. These crossing fibers constitute the habenular commissure.

The pineal gland, on the other hand, is a small structure that drops backwards and downwards from the posterior wall of third ventricle by a pineal stalk. The pulling force of the pineal gland sucks in part of the third ventricle into the base of the stalk. This gives rise to a pineal recess that is sandwiched between superior and inferior walls of the stalk. The habenular commissure comes to lie in the superior wall of the base of the pineal stalk.