Is unilateral cerebellum sufficient? Insights from new cases of cerebellar agenesis and literature review.

The clinical manifestations of adult-acquired cerebellar diseases often surpass those of congenital cerebellar diseases, suggesting the significant role of the cerebellum in the developing brain. Moreover, emerging evidence from structural and functional magnetic resonance imaging indicates that the cerebellum is implicated not only in motor functions but also in non-motor domains such as cognition, emotion, and language. However, delineating the specific extent of cerebellar development required to prevent deficits in either motor or non-motor functions remains challenging. In this study, we present two new cases of unilateral cerebellar agenesis. One individual leads a nearly normal life, while the other exhibits mild cognitive impairment, mild depression, and severe autism, but maintains normal motor function. Van der Heijden et al. (2023) revealed that the brain can compensate for some, but not all, perturbations to the developing cerebellum, including motor deficits and impairments in social behaviors. Therefore, we hypothesize that comparing structural images from our patients and reviewing pertinent literature may elucidate the reasons for the varied clinical manifestations observed in patients with cerebellar agenesis.