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Topic

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Cerebellar commissure

The cerebellar commissure refers to the white matter pathways that connect the two hemispheres of the cerebellum, allowing for interhemispheric communication. These commissural fibers cross the midline and are essential for the integration and coordination of bilateral cerebellar activity. The most prominent cerebellar commissure is the vermis, particularly its superior and inferior portions, which contain decussating fibers. The cerebellar commissure is not a distinct, standalone structure like the corpus callosum in the cerebrum, but rather a region encompassing various crossing fibers within the cerebellum. It plays a key role in synchronizing motor control and balance.

Synonyms

  • Vermal commissure

  • Commissural fibers of the cerebellum

  • Cerebellar decussation

  • Cerebellar interhemispheric fibers

Anatomy

  • Located at the midline of the cerebellum, mainly within the vermis (especially the superior and inferior vermis).

  • Composed of both superior cerebellar commissure (rostral, at the level of the superior vermis) and inferior cerebellar commissure (caudal, at the level of the inferior vermis).

  • Contains decussating fibers from the cerebellar cortex and deep cerebellar nuclei.

Arterial Supply

  • Supplied by branches of the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA).

  • The vermis, which contains the commissural fibers, receives blood from these arteries, with the SCA mainly supplying the superior part, and PICA/AICA supplying the inferior aspects.

Venous Drainage

  • Venous blood from the cerebellar commissure region drains into the superior cerebellar veins, inferior cerebellar veins, and ultimately into the straight sinus, transverse sinus, and sigmoid sinus.

  • The vein of Galen may also contribute to the drainage from the midline cerebellar region.

Function

  • Facilitates communication and coordination between the right and left cerebellar hemispheres.

  • Essential for the integration of bilateral motor activities, balance, and posture.

  • Helps synchronize and modulate muscle tone and voluntary movements on both sides of the body.

MRI Appearance

  • Appears as a midline structure of low to intermediate signal intensity on T1-weighted images and  intermediate signal intensity on T2-weighted images.

  • The commissural fibers are best seen in axial and coronal planes through the vermis.

  • No contrast enhancement is seen in normal commissural tissue.

  • Pathology (e.g., demyelination, tumors) may alter the signal characteristics.

CT Appearance

  • Not specifically visualized as a distinct structure on CT due to limited contrast between white and gray matter in the cerebellum.

  • May be inferred by identifying the midline cerebellar vermis and noting symmetry between the cerebellar hemispheres.

  • Pathological changes, such as infarction or hemorrhage, may make the commissure more conspicuous.

MRI images

Cerebellar commissure MRI 3T coronal image

CT image

Cerebellar commissure CT axial anatomy image -img-00001-00001