The prevalence of autism in cerebellar malformations: a systematic review and meta-analysis.

The cerebellum contributes to the control of movement, language, and sociability. Purkinje cells, the main output neurons of the cerebellar cortex, are reduced in cerebellar malformations (CMs) and in autism spectrum disorder (ASD). Thus, CMs may increase the risk for ASD. We conducted a meta-analysis to determine the prevalence of ASD in individuals with CMs. We searched PubMed, Embase, and APA PsycINFO for studies assessing ASD in patients with radiologically confirmed CMs. We evaluated risk of bias using Joanna Briggs Institute Checklists. Finally, we extracted data to calculate ASD prevalence and assess variation across CM subtypes. From 1,564 screened articles, 32 studies met inclusion criteria, encompassing 1,032 individuals with CMs. ASD prevalence was 31.2%, significantly higher than the general population rate (1 in 31). High heterogeneity was observed (I² = 72.3%; p < 0.0001). Vermis and cerebellar hypoplasia reliably contributed to the high ASD prevalence. Many studies had small sample sizes and used different metrics to diagnose autism. ASD is more common in individuals with CMs, especially vermis malformations, than in the general population. Early neurodevelopmental monitoring may benefit those with prenatally diagnosed CMs.