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Topic

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Habenular commissure

The habenular commissure is a small but significant bundle of nerve fibers situated in the dorsal aspect of the diencephalon, connecting the left and right habenular nuclei across the midline. It plays a crucial role in interhemispheric communication within the epithalamic region and is involved in integrating limbic and olfactory inputs with the midbrain. The habenular commissure is located superior to the pineal gland and just anterior to the posterior commissure. It is an important structure for neuroanatomical orientation in cross-sectional brain imaging.

Function

  • Connects the left and right habenular nuclei.

  • Facilitates bilateral communication between the habenular nuclei.

  • Involved in regulating emotional and motivational behaviors.

  • Influences pain processing, reproductive behavior, sleep-wake cycles, and reward pathways through connections with the limbic system and midbrain.

Arterial Supply

  • Primarily supplied by small branches of the posterior cerebral artery (PCA), specifically the posteromedial choroidal arteries.

  • Additional minor supply may arise from the medial posterior choroidal arteries.

Venous Drainage

  • Venous blood from the habenular commissure drains into the internal cerebral veins.

  • These veins ultimately contribute to the formation of the great cerebral vein (vein of Galen).

MRI Appearance

  • T1-weighted images: The habenular commissure appears as an intermediate signal intensity structure (isointense to slightly hyperintense  relative to the surrounding brain tissue).

  • T2-weighted images: Also demonstrates intermediate signal intensity (isointense to slightly hypointense compared to adjacent structures).

  • FLAIR sequences: The commissure is typically isointense to the surrounding brain, making it difficult to delineate unless there is adjacent pathology or edema.

CT Appearance

  • The habenular commissure is generally not individually visualized on non-contrast CT due to its small size and similar density to adjacent neural tissue.

  • May be inferred by its anatomical location relative to the pineal gland and posterior commissure in high-resolution studies.

MRI images

habenular commissure mri 3t axial image