Detection of early FXTAS motor symptoms using the CATSYS computerised neuromotor test battery

Carriers of the FMR1 premutation allele are at a significantly increased risk for a late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). This disorder is distinct from fragile X syndrome (FXS) with respect to the molecular etiology and clinical presentation. The primary features of FXTAS are late-onset intention tremor and gait ataxia. Associated features include parkinsonism, neuropsychological dysfunction, autonomic dysfunction and peripheral neuropathy. Our primary goal in this work was to investigate the usefulness of a quantitative neurological test battery implemented through the CATSYS instrumentation to identify pre-clinical symptoms of FXTAS. We have tested both premutation carriers with 70-199 repeats (N=62 males) and their low-repeat allele carrier siblings (N=27 males) identified through families with an individual affected with FXS. As expected, due to the sensitivity of the instrument, we were able to identify tremor in 23% of men who had not self-reported tremor, and ataxia in 30% of men who had not endorsed ataxia. Among subjects who self-reported tremor and ataxia, we found significant concordance between measures of the CATSYS system and self-report. Comparison of rates of these traits among premutation carriers and low-repeat allele carrier siblings are presented along with the minimum estimates of age-related prevalence.