Vagus nerve hypotrophy in genetically confirmed cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) patients

Objective: To assess bilateral vagus nerve cross-sectional area (CSA) in a cohort of molecularly confirmed CANVAS patients using ultrasound scans. Cerebellar Ataxia, Neuropathy and Vestibular Areflexia Syndrome (CANVAS) is a neurodegenerative disorder characterized by cerebellar ataxia, sensory neuronopathy, and bilateral vestibular areflexia. A pathogenetic role of the vagus nerve degeneration causing chronic cough, a typical CANVAS symptom, was hypothesized. Methods: We conducted a cross-sectional study including eight patients with CANVAS and six healthy controls. Bilateral vagus nerve cross-sectional area (CSA) was measured at the thyroid isthmus level. Descriptive statistics were performed, and group differences in CSA were assessed.Results: Vagus nerve CSA was statistically smaller in CANVAS patients compared with controls. Mean left CSA was 0.94 ± 0.22 mm2 in CANVAS vs 1.86 ± 0.13 mm2 in controls, while right CSA measured 1.16 ± 0.24 mm2 vs 2.14 ± 0.48 mm2. Conclusions: US scans reveal significant reduction of the vagus nerve CSA in genetically confirmed CANVAS patients. Significance: Reduction of vagus nerve CSA in genetically confirmed CANVAS patients supports the presence of vagal hypotrophy in this rare disorder. These findings suggest that vagus nerve ultrasonography may serve as a useful supportive biomarker for this form of neuronopathy.