Uncovering Neuropathic Pain in CANVAS: Lessons from a Case-Based Literature Review.
INTRODUCTION Cerebellar ataxia with neuronopathy and vestibular areflexia syndrome (CANVAS) is a rare, late-onset neurodegenerative disorder caused by biallelic intronic AAGGG repeat expansions in the RFC1 gene. Its phenotype is heterogeneous, ranging from isolated sensory neuronopathy to the full clinical triad. Although neuronopathy is present in the majority-if not all-of the cases, the prevalence and clinical significance of neuropathic pain remain insufficiently characterized. METHODS We report a genetically confirmed case of CANVAS in a 58-year-old woman presenting predominantly with asymmetrical neuropathic pain. Clinical, neurophysiological, vestibular, and genetic assessments were performed, with longitudinal follow-up over 3 years. Additionally, a case-driven systematic review and meta-analysis were conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A search was conducted in May 2026 in two databases (MEDLINE and Scopus) that identified cohorts of CANVAS cases with data on pain. Fourteen studies met our inclusion criteria. Pooled prevalence of neuropathic pain was calculated using a random-effects model. RESULTS The systematic review included 445 patients with CANVAS. The pooled prevalence of neuropathic pain was 43.2% (95% confidence intervals 34.0-52.9%) with moderate heterogeneity across these studies (I2 = 65%). Evidence from included studies suggests that pain may occur early and represents a significant contributor to disease burden. CONCLUSIONS Neuropathic pain is a frequent and potentially early manifestation of CANVAS, likely reflecting underlying sensory neuronopathy. CANVAS should be considered in patients with idiopathic sensory neuronopathy, even when pain is present. Early recognition and targeted genetic testing are essential to improve diagnosis and optimize patient management in this underdiagnosed condition.