Summary of CANVAS Syndrome
(Cerebellar Ataxia with Neuropathy and Vestibular Areflexia Syndrome)
Etiology
Cerebellar Ataxia with Neuropathy and Vestibular Areflexia Syndrome (CANVAS) is a neurodegenerative disorder characterized by a progressive triad of cerebellar ataxia, sensory neuropathy, and bilateral vestibular areflexia. It is now recognized as a genetic disorder caused by a biallelic repeat expansion in the RFC1 gene, leading to a neuronopathy affecting the dorsal root ganglia, cerebellum, and vestibular system (Dupré et al., 2021). The disease has an insidious onset, often presenting in the fifth or sixth decade of life, with a mean diagnostic delay of approximately ten years (Szmulewicz et al., 2014).
Signs and Symptoms
• Neurological: Progressive imbalance, ataxic gait, and postural instability that worsens in low-light conditions (Szmulewicz et al., 2014).
• Sensory Deficits: Non-length-dependent sensory loss, leading to impaired vibration sense, proprioception, and pain/temperature perception. Reflexes are often preserved or brisk (Dupré et al., 2021).
• Vestibular Dysfunction: Oscillopsia (visual instability during head movements) due to a loss of the vestibulo-ocular reflex (VOR) and impaired visual stabilization (Harrell et al., 2023).
• Oculomotor Abnormalities: Saccadic intrusions, downbeat nystagmus, and impaired smooth pursuit, indicative of cerebellar involvement (Harrell et al., 2023).
• Autonomic Dysfunction: Orthostatic hypotension, gastrointestinal dysmotility, and urinary dysfunction, present in a subset of patients (Dupré et al., 2021).
• Chronic Cough: A characteristic but often overlooked symptom, preceding neurological signs by decades (Szmulewicz et al., 2014).
Clinical Examination and Findings
• Neurologists and General Practitioners (GPs):
• Patients present with progressive imbalance and sensory deficits.
• Romberg’s test is positive due to proprioceptive loss.
• Dysarthria and dysphagia may develop later (Dupré et al., 2021).
• Vestibular Physiotherapists and Audiologists:
• Video head impulse test (vHIT) shows bilaterally reduced VOR gain.
• Dynamic visual acuity (DVA) testing reveals impaired visual stabilization (Harrell et al., 2023).
• Absent vestibular responses on caloric and rotational chair testing.
• MRI and Electrophysiology:
• Cerebellar atrophy, primarily affecting the vermis and hemispheres.
• Electromyography (EMG) reveals sensory neuronopathy with absent sensory nerve action potentials (Szmulewicz et al., 2014).
Treatment and Rehabilitation
There is no cure for CANVAS, and management is symptomatic.
• Physiotherapy:
• Vestibular rehabilitation improves balance, gait, and visual stabilization. Techniques include:
• Gaze stabilization exercises (VestAid-assisted therapy)
• Static and dynamic balance training
• Sensory integration exercises to compensate for sensory loss (Harrell et al., 2023).
• Medical Management:
• Orthostatic hypotension: Midodrine, fludrocortisone, and compression garments.
• Neuropathic pain: Pregabalin or amitriptyline (Szmulewicz et al., 2014).
• Assistive Devices:
• Canes and walkers for fall prevention.
• Corrective lenses for oscillopsia (Harrell et al., 2023).
Conclusion
CANVAS is a distinct, slowly progressive neurodegenerative disorder with significant functional implications. A multidisciplinary approach, including neurologists, vestibular physiotherapists, and audiologists, is essential for symptom management. Vestibular rehabilitation shows promise in improving functional outcomes, despite the irreversible nature of the disease (Dupré et al., 2021; Szmulewicz et al., 2014).
References
• Dupré, M., Hermann, R., & Froment Tilikete, C. (2021). Update on Cerebellar Ataxia with Neuropathy and Bilateral Vestibular Areflexia Syndrome (CANVAS). The Cerebellum, 20(4), 687-700. https://doi.org/10.1007/s12311-020-01192-w
• Harrell, R.G., Cassidy, A.R., Klatt, B.N., Hovareshti, P., & Whitney, S.L. (2023). Vestibular rehabilitation in cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS): A case report. Journal of Otology, 18, 199-207. https://doi.org/10.1016/j.joto.2023.06.004
• Szmulewicz, D.J., McLean, C.A., MacDougall, H.G., Roberts, L., Storey, E., & Halmagyi, G.M. (2014). CANVAS: An update on clinical presentation, investigation, and management. Journal of Vestibular Research, 24, 465-474. https://doi.org/10.3233/VES-140536