Chiari I Malformation as a Human Disease Model of Cerebellar Cognitive-Affective Dysfunction.

Chiari malformation type I (CM1) is traditionally viewed as a structural disorder of the posterior fossa characterized by cerebellar tonsillar herniation. However, growing evidence indicates that CM1 is frequently accompanied by disturbances in cognition, emotion, and behavior that cannot be fully explained by pain, hydrocephalus, or radiographic severity alone. Advances in cerebellar neuroscience highlight the cerebellum's critical role in higher-order cognition and affect through distributed cerebrocerebellar networks. Here, we synthesize neuropsychological, neuroimaging, developmental, and clinical evidence to reframe CM1 as a disorder of cerebellar cognitive affective dysfunction. Across pediatric and adult populations, CM1 is associated with domain-specific inefficiencies in attention, executive control, working memory, visuospatial processing, language fluency, and social cognition, closely paralleling the cerebellar cognitive affective syndrome (CCAS). Network-level imaging studies further demonstrate disruption of cortico-ponto-cerebellar and cerebello-thalamo-cortical connectivity, supporting a distributed rather than focal model of disease. We highlight the modulatory roles of development and chronic pain, critically evaluate cognitive outcomes after posterior fossa decompression, and discuss implications for assessment and future research. Recognizing CM1 as a disorder of cerebellar network integration has important consequences for clinical care and mechanistic investigation.