Kisagy

Kisagy, in Hungarian anatomy, refers to the cerebellum, a brain structure located in the posterior cranial fossa beneath the cerebral hemispheres and behind the brainstem. It plays a critical role in coordinating voluntary movement, maintaining posture and balance, and contributing to motor learning and the timing of movements.

Anatomy: The cerebellum consists of two hemispheres connected by the vermis and is traditionally divided into the anterior lobe, posterior lobe, and flocculonodular lobe. The cerebellar cortex has three layers—molecular, Purkinje, and granular—and gives rise to deep cerebellar nuclei (dentate, interposed, fastigial). Output from these nuclei modulates motor and premotor circuits via the thalamus and brainstem. The main arterial supply comes from the posterior inferior cerebellar artery (PICA), the anterior inferior cerebellar artery (AICA), and the superior cerebellar artery (SCA).

Function: It integrates sensory input from the spinal cord, vestibular system, and cerebral cortex through mossy and climbing fibers, enabling precise timing, coordination of multisensory information, balance maintenance, and error correction during movement. The cerebellum also participates in some cognitive and affective processes, with cerebellar cognitive and affective syndrome described in certain lesions.

Clinical relevance: Damage to the kisagy can cause ataxia, dysmetria, intention tremor, decomposition of movement, and nystagmus, often with hypotonia in acute stages. Causes include stroke, tumors, degenerative ataxias (such as spinocerebellar ataxias), alcohol-related cerebellar degeneration, and acquired injuries. Modern imaging helps localization and diagnosis.

Etymology and usage: In Hungarian, kisagy literally means “little brain” and is the standard term for the cerebellum in medical and educational contexts.