CTNNB1-related disorders: clinical and radiological contributions from a French cohort.

CTNNB1 monoallelic pathogenic variants account for up to 4% of genetically determined cerebral palsy cases, yet their phenotypic spectrum remains poorly defined. We retrospectively analyzed 25 individuals with pathogenic CTNNB1 variants using medical records and a questionnaire. Data included genetic variants, perinatal history, developmental milestones, behavioral characteristics, head growth, feeding, sleep difficulties, neurological and ophthalmological assessments. Brain MRIs were reviewed by expert neuroradiologists. Twenty-two distinct heterozygous variants were identified. Microcephaly occurred in 16/22 patients. All exhibited global developmental delay, independent walking was achieved at a mean age of 2.1 years, with regression in 4/16 independent walkers. Behavioral disorders were frequent, as were oral sensorimotor disorders (21/25) and sleep disturbances (13/21). Lower limb hypertonia was present in 22/25 patients [spastic (8) and/or dystonic (11)]. Unstable gait were common among ambulatory patients. Exaggerated startle reactions, often since birth, were reported in 16/21. Exudative vitreoretinopathy was identified in 3/5 patients with retinal angiography. Brain MRI (19 patients) showed: thickening of anterior commissure (8), frontal lobe hypoplasia (9), widening of superior vermian sulci (10) and corpus callosum anomalies (7). This study broadens the spectrum of CTNNB1-related syndrome, reporting a complex motor phenotype combining (i) gait disturbances related to dystonic or non-dystonic hypertonia and unsteadiness, sometimes associated to dystonia in other body parts (ii) possible deterioration of motor achievements over the course of the disease (iii) an exaggerated startle reflex. New non-specific brain anomalies are precisely described. Our work underscores the need for registries and longitudinal studies to refine characterization and guide future therapies.