Pathogenic variants in the β1-catenin (CTNNB1) gene have been identified in patients with various diseases, including syndromic intellectual disability, autism spectrum disorder, familial exudative vitreoretinopathy, and neurodevelopmental disorder with spastic diplegia and visual defects (NEDSDV). We report on the clinical, genetic, neuroimaging, and neurophysiological data of a 15-year-old patient with complex hereditary spastic paraplegias with exotropia, dyskinesia, and cerebellar signs and a so-far unreported demyelinating (mainly sensory) polyneuropathy in her lower limbs. She carries the novel, de novo, likely pathogenic heterozygous c.603_605delinsAATA, p.(Met202Ilefs*6) frameshift variant in the CTNNB1 gene. Although peripheral neuropathy was not previously associated with NEDSDV, in light of the role of β1-catenin as a junction protein in the peripheral as well as in the central nervous system documented in experimental studies, it might represent a causally linked and under-reported finding to be further explored.