Motor disabilities and effects of thyrotropin-releasing hormone on ataxia of spinocerebellar degeneration.

Fine aiming task was studied quantitatively in 20 patients with spinocerebellar degeneration (SCD) and 8 normal control subjects, utilizing a manual control system with random-step input signal. The transfer function of the system was an integral function and ability to perform a 'differentiating action' compensating for this integral function was analyzed. This 'differentiating action' was defective in all patients with SCD and was normal in all control subjects. A display of the dynamic characteristics of subjects on the plane defined by principal component analysis of the parameters showed definite delineation of the characteristics of patients from those of the controls. The intramuscular injection of thyrotropin-releasing hormone (TRH) resulted in an increase in amplitude of manipulation, a shortening of reaction time and consequently an improvement in motor disabilities in 65% of 20 patients with SCD.