cerebellärens

Cerebellärens (the cerebellum) is the principal structure of the hindbrain involved in motor coordination. Located posterior to the brainstem, it lies in the posterior cranial fossa and consists of two hemispheres connected by a central vermis. The surface is folded into folia and is divided into lobes: the flocculonodular lobe, the anterior lobe, and the posterior lobe. The cerebellar hemispheres coordinate limb movements, while the vermis regulates posture and gait. The posterior fossa contains three paired cerebellar peduncles: the superior, middle, and inferior, which connect the cerebellum with the brainstem and spinal cord. Deep within the cerebellum are four pairs of deep nuclei—the dentate, emboliform (interposed), globose, and fastigial—which serve as the primary output channels.

Functional subdivisions include the vestibulocerebellum (balance and eye movements), the spinocerebellum (limb movement coordination and proprioception), and the cerebrocerebellum (planning and timing of movements). Afferent signals reach the cerebellar cortex mainly via mossy fibers; climbing fibers from the inferior olive also provide powerful input. Purkinje cells, the main cortical output neurons, inhibit the deep cerebellar nuclei, shaping motor commands that are then transmitted to the thalamus and brainstem.

Clinical relevance: cerebellar dysfunction produces ataxia, dysmetria, intention tremor, dysdiadochokinesia, hypotonia, and nystagmus. Causes include infarcts or hemorrhages in cerebellar arteries (PICA, AICA, and the superior cerebellar artery), tumors, degeneration (as in spinocerebellar ataxias), and blunt trauma.

Developmentally, the cerebellum arises from the hindbrain (rhombencephalon) and undergoes extensive foliation.