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WINTER 2023 InTouch | 17 Physical examination, vestibular function testing, video-oculography, nerve conduction studies and MRI of the brain are normally conducted to detect signs and symptoms of CANVAS. CANVAS, first clinically defined in 2011, is an easy-to-remember acronym that describes an adult- onset slowly progressive neurologic disorder that has an average age of onset of 50-60 years. People with CANVAS have cerebellar ataxia (coordination problems), neuropathy (peripheral nerve damage), and vestibular areflexia (loss of vestibular function) and combined they form a recognisable syndrome affecting balance and gait, which is progressive, worsening over time. The vestibular system is a collection of structures in your inner ear that provides you with your sense of balance and an awareness of your spatial orientation (meaning a sense of whether you are right-side up or upside-down). Your brain then integrates that information with other sensory information from your body to coordinate smooth and well-timed body movements. Common features of this condition include “dolls head reflex” upon examination, which is an impaired ability of the eye velocity to match head velocity when turning the head from side to side. Involuntary eye movements (nystagmus) can occur in some individuals with the condition as well as difficulty articulating speech (dysarthria). Individuals with this condition may have problems standing and CANVAS YOUR CONDITION IN REVIEW will show a positive Romberg sign which means they experience loss of balance when the eyes are closed. Loss of coordination of the limbs can also occur. Other presenting features can include a persistent cough, dysesthesia (an abnormal unpleasant sensation felt when touched, caused by damage to peripheral nerves), oscillopsia (a visual disturbance in which objects in the visual field appear to oscillate), dizziness, and falls. Brain MRI of individuals with CANVAS will show cerebellar atrophy. CANVAS is a rare but likely under- diagnosed disorder. It is inherited in an autosomal recessive pattern. This means two altered genes are inherited, one from each parent. The parent’s health is unaffected as the condition requires two altered genes to occur. Diagnosis Physical examination, vestibular function testing, video-oculography, nerve conduction studies, and MRI of the brain are normally conducted to detect signs and symptoms of this condition. In 2019, it was established that CANVAS is caused by an alteration in a gene called RFC1 (replication factor C) on chromosome 4. Usually, the gene contains a simple tandem pentanucleotide AAAAG repeat of 11 Common features of this condition include “dolls head reflex” upon examination, which is an impaired ability of the eye velocity to match head velocity when turning the head from side to side. Autosomal recessive Carrier mother Affected Unaffected Carrier father 50% chance carrier 25% chance affected 25% chance unaffected When two carrier parents have a child, there are three possible outcomes. With each pregnancy, there is a 25% chance that the child will be affected.