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The cerebellar and spinocerebellar dysfunction seen in Friedreich ataxia (FRDA) has known effects on motor function. Recently, it was suggested that people with FRDA may also have impairment in motor planning, either because of cortical pathology or because of cerebello-cortical projections. Fifteen adults with FRDA and 15 matched controls completed a task requiring reciprocating movements between two buttons on a tapping board. Occasionally there was one of three "oddball" stimuli requiring reprogramming of movement. These were change in (1) direction, (2) extent or (3) direction and extent. We hypothesized that people with FRDA would have prolonged movement times due to their movement disorder, and that changes in preparation time would be affected in a way similar to controls, unless there was impairment in motor planning in FRDA. Movement execution and, to a lesser degree, movement preparation were impaired in individuals with FRDA. We argue this points to disturbed cortical function. There was a significant negative correlation between age of onset and all three reprogramming conditions, suggesting an impact of FRDA on developing motor planning. Future studies will be required to establish whether this dysfunction is due to cerebellar impairment interrupting cerebro-ponto-cerebello-thalamo-cerebral loops, primary cortical pathology or a combination of the two.

Friedreich Ataxia (FRDA) is the commonest inherited ataxia. Clinical trials of pharmaceuticals are increasingly being conducted in this condition. This requires the most accurate outcome measures to enable trials to be conducted with a minimum number of subjects in the shortest time frame and to minimize the risk of false negative results. Upper limb function is a major area of morbidity in FRDA. We therefore have compared the performance of three tests of upper limb function in FRDA: the Nine Hole Peg Test (9HPT), Box and Blocks Test (BBT) and Jebsen Taylor Hand Function Test (JTHFT). This study was undertaken to ascertain the best test for inclusion in a Friedreich Ataxia Functional Composite (FAFC) test for use in clinical studies and therapeutic trials. The three tests were administered to the dominant and non-dominant upper limbs of 38 individuals with genetically proven FRDA on two occasions, 12 months apart. The results of testing were correlated with the following disease parameters; age at disease onset, disease duration and score for the Friedreich Ataxia Rating Scale (FARS). The responsiveness to change of each test was assessed by measuring the effect size and calculations of the number of subjects required for similarly powered therapeutic trials. Results for all tests correlated significantly with disease duration and FARS score. The only test scores that changed significantly over 12 months were those for the non-dominant 9HPT and BBT. Scores for these two tests also had the largest effect sizes and required the fewest subjects for similarly powered therapeutic trials. We conclude, therefore, that the non-dominant 9HPT and BBT are the best tests for inclusion in a FAFC. Since the 9HPT has already been suggested for inclusion in a FAFC, we recommend that this test is used but that it is the non-dominant limb that is tested.