Neurophysiological evaluation in children with Friedreich's ataxia

Introduction: In children with Friedreich's ataxia (FRDA children), clinical ataxia outcomes are hardly substantiated by underlying neurophysiological parameters. In young FRDA children, some reports (based upon International Cooperative Ataxia Rating Scale scores ([CARS)) mention transient neurological improvement upon idebenone treatment. However, these outcomes are obtained with adult instead of pediatric reference values. It is unknown whether age-related neurophysiological parameters can really substantiate neurologic improvement. Aim: In young FRDA children, we aimed to determine longitudinal neurophysiological parameters during idebenone treatment. Methods: During a two-year study period, 6 genetically proven FRDA children with cardiomyopathy (6-18 years) were longitudinally assessed for neurophysiological parameters [sensory evoked potentials (SEPs), F response, peripheral nerve conduction and dynamometry] in association with age-matched ICARS-scores. Results: In all FRDA children, SEPs remained absent during the two-year study period. Peroneal nerve conduction velocity declined (from -1SD to -2SD: p<.05), whereas F responses remained essentially unaltered. Total muscle force and leg muscle force decreased (from -2 to -3SD and -2.5 to -3.5SD: both p <.05) and age-related ICARS-scores deteriorated (median increase +41%; p<.05). Conclusion: In FRDA children, age-related neurophysiological and ataxia parameters deteriorate during idebenone treatment Although we cannot exclude some (subjective) disease stabilization, age-related neurophysiological parameters do not substantiate neurologic improvement. (C) 2009 Elsevier Ireland Ltd. All rights reserved.