TY - JOUR T1 - Diagnostic yield of testing for <em>RFC1</em> repeat expansions in patients with unexplained adult-onset cerebellar ataxia JF - Journal of Neurology, Neurosurgery &amp; Psychiatry JO - J Neurol Neurosurg Psychiatry DO - 10.1136/jnnp-2020-323998 SP - jnnp-2020-323998 AU - Sien Hilde Van Daele AU - Sascha Vermeer AU - Amélie Van Eesbeeck AU - Laura Lannoo AU - Valérie Race AU - Philip van Damme AU - Kristl Claeys AU - Wim Vandenberghe Y1 - 2020/07/30 UR - http://jnnp.bmj.com/content/early/2020/07/30/jnnp-2020-323998.abstract N2 - Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is an adult-onset, slowly progressive neurodegenerative disorder characterised in its full form by cerebellar ataxia, sensory neuropathy and bilateral vestibulopathy. Autonomic dysfunction and dry cough are also frequent features. CANVAS is usually sporadic, but occasionally occurs in siblings. Recently, a biallelic intronic AAGGG repeat expansion (AAGGG)exp in RFC1 was identified as the cause in almost all tested familial cases with full CANVAS syndrome.1 2 Interestingly, biallelic (AAGGG)exp in RFC1 were also found in 22% of sporadic, previously idiopathic late-onset ataxia cases.1 The percentage of positive cases increased to 63% if only sporadic patients with combined late-onset cerebellar ataxia and sensory neuropathy were considered, and to 92% in sporadic cases with full CANVAS.1 In a cross-sectional description of 100 patients with biallelic RFC1 (AAGGG)exp, all cases had sensory neuropathy on nerve conduction studies (NCS), while only 79% of cases had cerebellar involvement.3 Whether biallelic RFC1 (AAGGG)exp can cause cerebellar ataxia without sensory neuropathy, remains uncertain. Here, we determined the diagnostic yield of testing for RFC1 repeat expansions in a single-centre cohort of unexplained adult-onset ataxia cases.We included all index patients with ataxia who were evaluated at University Hospitals Leuven in the Movement Disorders Clinic between March 2005 and September 2019 or the Neuromuscular Clinic between January 2000 and December 2018 and fulfilled the following criteria: (1) onset age 18 years or older (onset as early as 19 years has been reported in an RFC1 case)3; (2) ataxia as prominent clinical feature; (3) clinical evidence for cerebellar … ER -