[A quantitative analysis of ataxia in the upper limbs]

By using a transparent digitizer and a personal computer, we tried a quantitative analysis of ataxia in the upper limbs. A total of 25 upper extremities of 13 patients with spino-cerebellar degeneration (SCD) and 140 upper extremities of 70 normal volunteers were tested by two types of tasks. One was the free speed trace of a circle presented on the display (free circle), and the other was the pursuit of a target moving on a circle at a fixed speed (pursuit circle). The digitizer was put on a color display stabilized horizontally. For 1024 points with a 25 msec sampling time, the trajectory of the stylus pen was transmitted to the computer in real time. Circle diameters of 3 cm and 6 cm were selected. The target rounded the circle at a speed of 6 or 3 times per 1024 points. The mean velocity (MV), mean acceleration (MA), and MA/MV ratio were calculated for the extent of one circle period. And the coefficient of variation (CV) of the shifted distance in each sampling time and the power spectrum by Fast Fourier Transform (FFT) to the acceleration wave were calculated for the total input data. In the free circles, the MV and logarithm of MA varied widely and showed positive correlations. In contrast, those of the pursuit circles converged narrowly near the values of the target. On the other hand, in the SCD group, many patients could not draw the small free circle.(ABSTRACT TRUNCATED AT 250 WORDS)