Repetitive finger movement performance differs among Parkinson’s disease, Progressive Supranuclear Palsy, and spinocerebellar ataxia

BACKGROUND Differentiating movement disorders is critical for appropriate treatment, prognosis, and for clinical trials. In clinical trials this is especially important as effects can be diluted by inclusion of inappropriately diagnosed participants. In early disease duration phases, disorders often have overlapping clinical features, such as impairments in repetitive finger movement, making diagnosis challenging. The purpose of this pilot study was to examine and compare repetitive finger movement performance in participants diagnosed with idiopathic Parkinson's disease, Progressive Supranuclear Palsy, and spinocerebellar ataxias. METHODS Participants completed an unconstrained index finger flexion/extension movement (i.e. finger tap) in time with an incremental acoustic tone. Measures of movement rate, movement amplitude, and coefficient of variation were compared among groups. RESULTS Significant differences between groups were revealed for movement rate at faster tone rates. Participants with Parkinson's disease tended to tap faster than the tone rate while participants with Progressive Supranuclear Palsy and spinocerebellar ataxia tended to tap slower. No significant differences were revealed for movement amplitude, but participants with spinocerebellar ataxia demonstrated greater variance in amplitude than participants with Parkinson's disease. CONCLUSION Quantitative analysis of repetitive finger movement performance at faster rates may be helpful to differentiate Parkinson's Disease, Progressive Supranuclear Palsy and spinocerebellar ataxia.