Surface emg rn myotonic dystrophy

We performed a motor point stimulation protocol on tibialis anterior of MyD patients and recorded following parameters: average rectified value (ARV), median frequency of power spectrum (MDF), mean conduction velocity (CV). The curves fitting ARV measurements showed an opposite trend in the two groups However it was possible to distinguish two subgroups in MyD: those patients without strength deficit showed an ARV decreasing pattern, while those with strength deficit had an increasing trend (like controls); MDF showed a significant decrement only at 5 sec, in MyD respect to controls; CV initial values were significantly lower fn MyD. At 5 sec and at the end of stimulation (30 sec) the A per cent was not significantly different. These results revealed: a) decrease in the amplitude of the action potential during the stimulation probably due to a slightly depolarized membrane and to a potassium accumulation in the extracellular compartment; b) abnormal lengthening of the depolarization zone in the first sec of the sustained contraction, c) decreased mean fibers size.