Vestibular assessment in cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS): a preliminary study

Abstract

Background: Cerebellar Ataxia with Neuropathy and Cerebellar Vestibular Syndrome (CANVAS) is a slow progressive, recessively inherited, neurodegenerative disease of late onset. It is characterized by progressive imbalance due to a combination of cerebellar, somatosensory, and vestibular impairment with normal hearing. The main neurological symptoms include balance, dizziness, falls, sensory complaints, and oscillopsia due to the presence of nystagmus associated with cerebellar ataxia and vestibulo-ocular reflex dysfunction (VOR). More recently, the disease entity has expanded to atypical phenotypes, including chronic neuropathy without cerebellar ataxia or vestibular areflexia. With the progression of the disease, patients may develop dysarthria, dysphagia, and autonomic dysfunction symptoms. Chronic cough may precede the onset of neurological symptoms within three decades. In addition, some patients may feature hypohidrosis, orthostatic hypotension, and neurogenic pains. Objective: To describe the alterations observed in vestibular testing in patients with CANVAS and to assess the quality of life by applying the Activities-Specific Balance Confidence (ABC) scale. Methods: Fifteen patients who met the clinical and genetic criteria for CANVAS were assessed using the following procedures: clinical history, otorhinolaryngological assessment, vestibular exam and application of the ABC scale. Results: The main complaints found in clinical history were gait disturbances (86.7%), headache (73.3%), dizziness (60%), paresthesia, dysarthria, and fatigue, (53.3%). In the vestibular exam, the caloric test (80%), gaze nystagmus, dysmetric saccades, and smooth pursuit deficit (53.3%) presented the highest rates of abnormalities, with prevalence of central vestibulopathy in 60% of cases. The ABC scale revealed 100% difficulty in the level of confidence in performing specific daily activities. Conclusion: Vestibular testing can be a tool to help investigate CANVAS, additional and accurate clinical approach and molecular genetics testing. The possibility of CANVAS should be considered in patients with bilateral vestibular deficit. The ABC scale showed difficulty in performing tasks that require balance, trunk and head flexion. Its result proved to be useful in assessing the risk of falls, reinforcing the importance of therapeutic intervention in this population.