title: Routine clinical testing underestimates proprioceptive deficits in Friedreich's ataxia.
abstract: Friedreich's ataxia (FA) is the most common recessive ataxia in the Western world with degeneration of dorsal root ganglia neurons as its major neuropathological hallmark. The sensitivity of clinical tools commonly used for the assessment of the proprioceptive component of FA is currently unknown. We hypothesised that current clinical testing underestimates proprioceptive deficits in FA patients. Such an underestimation would hamper our understanding of the components of FA, the monitoring of disease progression, and the detection of deficits in the current advent of drug trials. We compared clinical tests for joint position sense (JPS) and vibration sense (VS) to a test of spatial position sense (SPS) that examines localisation of both hands across a horizontal 2D space. We tested 22 healthy controls to derive a cut-off for the SPS. Eleven patients with genetically confirmed FA participated in this study. All 11 FA patients were impaired in the SPS test. Two patients showed unimpaired JPS and VS. Two additional patients showed unimpaired JPS, while two other patients unimpaired VS. The SPS test was more sensitive and revealed deficits potentially earlier than clinical screening tests. Only the SPS showed a positive correlation with ataxia severity. The SPS was more sensitive than the commonly used JPS and VS. Thus, our results indicate that proprioceptive deficits in FA start earlier and are more severe than indicated by routine standard clinical testing. The contribution of proprioceptive deficits to the impairment of FA patients might therefore indeed be underestimated today.
authors.affiliation: Division of Neuropsychology, Hertie-Institute for Clinical Brain Research, Centre for Integrative Neuroscience, Eberhard Karls University, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany.
authors.forename: Svenja
authors.initials: S
authors.lastname: Borchers
authors.forename: Matthis
authors.initials: M
authors.lastname: Synofzik
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kiely
authors.forename: Marc
authors.initials: M
authors.lastname: Himmelbach
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D005621:Friedreich Ataxia / Q000150:complications*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology; D020886:Somatosensory Disorders / Q000175:diagnosis* / Q000209:etiology*; D055815:Young Adult
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