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Introduction

CANVAS syndrome (Cerebellar Ataxia, Neuropathy, and Vestibular Areflexia Syndrome) is a rare but increasingly recognized neurodegenerative disorder. The discovery of biallelic intronic repeat expansions in the RFC1 gene has revolutionized our understanding of this condition. In this article, we examine a detailed case (Case 2) of CANVAS syndrome associated with RFC1 mutations, highlighting the core clinical features, diagnostic approach, and relevant genetic findings.

Clinical Features in RFC1 Case 2

Case 2 is a 62-year-old male who presented with a 7-year history of progressive imbalance and unsteady gait. The key symptoms included:

• Cerebellar ataxia – limb incoordination, dysarthria, and wide-based gait.
• Neuropathy – predominantly sensory, with reduced vibration sense, impaired joint position sense, and areflexia.
• Vestibular areflexia – oscillopsia (blurred vision during head movement) and abnormal head impulse test.
• Chronic cough – reported in some RFC1 patients, present in this case for over 10 years prior to ataxia onset.

Neurological examination confirmed bilateral gaze-evoked nystagmus, dysmetria on finger-to-nose testing, and a positive Romberg sign. Nerve conduction studies revealed severe sensory axonal neuropathy without significant motor involvement.

Genetic Confirmation: RFC1 Repeat Expansion

Genetic testing in Case 2 identified a biallelic intronic AAGGG repeat expansion in the RFC1 gene. This specific repeat motif (AAGGG) is the most common pathogenic allele among CANVAS patients. The expansion was detected using long-read sequencing and repeat-primed PCR. Both parents were asymptomatic carriers, consistent with autosomal recessive inheritance.

The confirmation of the RFC1 expansion provided a definitive diagnosis and avoided unnecessary investigations for other causes of late-onset ataxia.

Diagnostic Pathway

This case underscores the importance of considering CANVAS in patients with the triad of ataxia, neuropathy, and vestibular areflexia, especially when there is a chronic dry cough and a family history suggestive of recessive inheritance.

Management and Prognosis

There is currently no disease-modifying treatment for CANVAS syndrome. Management in Case 2 focuses on symptomatic and supportive care:

• Physical therapy for gait and balance training.
• Use of walking aids (cane, walker) to prevent falls.
• Speech therapy for dysarthria.
• Occupational therapy for fine motor coordination.
• Monitoring for complications such as aspiration pneumonia.

The prognosis is slowly progressive, with most patients remaining ambulatory for 10–20 years after onset. Case 2 continues to live independently with moderate assistance.

Conclusion

CANVAS syndrome due to RFC1 biallelic repeat expansions is an important cause of late-onset ataxia. Case 2 illustrates the typical clinical trajectory and highlights the crucial role of genetic testing for accurate diagnosis. Increased awareness among neurologists is essential for timely identification and management of this condition.

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see also: CANVAS_case