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Superior semilunar lobule of cerebellum

The Superior Semilunar Lobule is a prominent structure on the superior surface of the cerebellar hemisphere. Located posterolaterally, it forms a crescent-shaped area on each side of the cerebellum, bordered medially by the primary fissure and laterally and inferiorly by the horizontal fissure. It is part of the posterior lobe and is involved in integrating sensory input, particularly from the limbs, for coordination of voluntary movements.

Synonyms

  • Lobulus semilunaris superior (Latin)

  • Superior semilunar lobule (common anatomical term)

  • Lobulus semilunaris anterior (in some older texts, but this is less common and may refer to a slightly different region)

Arterial Supply

  • Supplied primarily by branches of the Superior Cerebellar Artery (SCA).

  • Smaller contributions may come from the Anterior Inferior Cerebellar Artery (AICA) depending on anatomical variation.

  • The SCA arises from the basilar artery and supplies the superior aspects of the cerebellar hemispheres, including the superior semilunar lobule.

Venous Drainage

  • Drained mainly by the Superior Cerebellar Veins.

  • These veins empty into the Great Cerebral Vein (Vein of Galen) and the Straight Sinus.

Function

  • Integrates proprioceptive sensory input from the limbs, especially the upper extremities.

  • Plays a crucial role in motor coordination, timing, and precision of voluntary movements.

  • Involved in the regulation of muscle tone and possibly in higher cognitive functions related to movement.

MRI Appearance

  • Appears as a well-defined, crescent-shaped region on the superior surface of the cerebellar hemisphere.

  • On T1-weighted images: Isointense to the rest of the cerebellar cortex.

  • On T2-weighted images: Also isointense to other cerebellar folia, unless affected by pathology (e.g., atrophy or infarct).

  • Fissures (primary and horizontal) are seen as hypointense (dark) lines demarcating its boundaries.

CT Appearance

  • The cerebellar cortex, including the superior semilunar lobule, is not distinctly visualized on non-contrast CT due to low contrast resolution.

  • Can be inferred as part of the cerebellar hemisphere lateral to the vermis and superior to the horizontal fissure.

  • Pathology such as ischemia, hemorrhage, or atrophy may highlight this lobule more clearly by loss of normal cerebellar tissue density.

CT image

Superior semilunar lobule of cerebellum CT axial anatomy image -img-00001-00001