[The study of denervation-reinnervation process in motor neuron disease and benign neuron disorders]

To study peculiarities of chronic partial denervation (CPD), needle electromyography (EMG) of the neck, upper and lower extremity muscles on the less affected side was performed in 25 patients with definite motor neuron disease (MND) and in 9 patients with benign motor neuron disorders (BMND) with 2-month-long follow-up interval. Normal values of EMG parameters for muscle studied and test-retest correlation coefficient were calculated in 35 healthy volunteers. In MND on the early stages (1 and 2) of CPD, duration and amplitude of motor unit potentials (MUPs) correlated negatively while on the later stages (3A, SB, 4 and 5) the correlations were positive, but only in muscles within the site of onset. There was no significant predominance of duration and amplitude of MUPs in those muscles. MUPs amplitude was significantly higher in patients with MND with predominant lower motor neuron involvement (p < 0.05). In muscles with MUPs duration higher than--20% and increased amplitude, MUPs duration decreased within the site of onset up to the second study. In BMND, MUPs duration and amplitude never decreased in follow-up. These parameters were significantly higher in BMND than in MND (p < 0.0001) in less affected muscles (without paresis). In contrast to BMND, no lag of paresis behind the CPD stage was observed in MND. The data obtained suggest a recurrent and forward mode of CPD on late stages and allow to differentiate slowly progressive MND and BMND in the single as well as in repeated study after a short period of time.