Study of L-dopa Treatment in Patients With a Neurodevelopmental Disorder (CTNNB1 Gene)

Neurodevelopmental disorders (NDD) encompass conditions that impair cognitive and/or emotional development in children, significantly impacting school, social, and family life. They are often linked to genetic causes and, in most cases, lack curative treatment. Among these disorders, monoallelic variations in the CTNNB1 gene cause a rare syndrome known as NEDSDV (Neurodevelopmental disorder with spastic diplegia and visual defects, OMIM: 615075). About twenty patients are reported in France. This syndrome is characterized by global developmental delay, intellectual disability, axial hypotonia, autistic traits, microcephaly, and sometimes ocular anomalies. The clinical profile resembles that of cerebral palsy, and CTNNB1 syndrome is considered a genetic form of this condition, accounting for roughly 4% of cases where a gene has been identified. Motor impairment is a core feature, with a wide range of movement disorders. Research remains limited, except for a recent publication. Dystonic hypertonia of the lower limbs is frequently described, more pronounced distally than proximally, without pyramidal signs. Spasticity is less common. Gait has been poorly studied: it may be absent or, when acquired, unstable, often tiptoe, and sometimes broad-based, resembling ataxia despite the absence of cerebellar signs. These motor features are difficult to detect before one year of age. To date, no longitudinal studies exist on motor or cognitive progression in CTNNB1 patients; available data are cross-sectional and do not suggest cognitive decline. From a pathophysiological perspective, the CTNNB1 gene encodes β-catenin, a key protein in cell adhesion and Wnt signaling, involved in cell differentiation and tissue homeostasis. It plays an essential role in embryonic brain development, particularly neuritogenesis and synaptic organization, with a specific impact on dopaminergic structures in the midbrain. Knock-out animal models show severe reduction in dopaminergic neurogenesis.