Inferior semilunar lobule

At a glance

English

Inferior semilunar lobule

Latin (TA2)

Lobulus semilunaris inferior

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the inferior semilunar lobule

The inferior semilunar lobule is one of the main lobules of the cerebellar hemisphere. It is crescent-shaped, as its name says, and forms much of the posterior part of the lower surface of each hemisphere. In modern terminology it is the second crus of the ansiform lobule, and in Larsell's numbered scheme it belongs to hemispheric lobule H VIIA.

Its upper border is the horizontal fissure, which runs round the posterior and lateral margin of the cerebellum and separates it from the superior semilunar lobule above. Below and in front lies the gracile lobule, and beyond that the biventral lobule. Towards the midline its folia narrow and become continuous with the tuber of the vermis. Its outer surface rests in the posterior cranial fossa, against the occipital bone below the transverse sinus.

Together with the superior semilunar lobule it makes up the ansiform lobule, the largest part of the human cerebellar hemisphere, which has expanded greatly alongside the cerebral cortex. This part of the cerebellum receives most of its input from the cerebral cortex through the pontine nuclei and the middle cerebellar peduncle, and its Purkinje cells send their output to the dentate nucleus. From there fibres pass through the superior cerebellar peduncle to the opposite thalamus and on to the motor and prefrontal cortex. The loop helps with the planning and timing of skilled limb movements and is also thought to take part in cognitive tasks.

Damage to the hemisphere produces signs on the same side as the lesion, such as intention tremor, past-pointing and difficulty with rapid alternating movements.

Function and supply

Function

Part of the lateral cerebellar hemisphere linked with the cerebral cortex through the pons and dentate nucleus: helps plan and time skilled limb movements on the same side.

Blood supply

Branches of the posterior inferior cerebellar artery on the inferior surface of the hemisphere.