[Signs of aging of the peripheral motor neurons based on electromyographic studies]

Sixty healthy subjects of either sex aged from 15 to 75 years were examined. Electromyographic records were obtained by the one-step automatic histogram analysis method according to Hausmanowa-Petrusewicz and Kopeć, and by the classic method of quantitative electromyography. In each case 4 muscles were examined: deltoid (Dlt), rectus m. of thigh (RF), short abducens m. of thumb (APB), short extensor of fingers (EDB). In both methods the mean duration of motor unit potential, the amplitude of single motor unit potential, the amplitude of effort record and the density of potentials were determined and correlated with age. The duration of motor unit potentials in the classic EMG record was correlated statistically significantly with the age in all muscles (in agreement with Buchthal). The number of parameters correlating with age and the significance of this correlation were highest in the records from lower extremity muscles, particularly in EDB. This could depend on age-related summation of subclinical signs of peroneal nerve damage, since this nerve is exposed to frequent microtraumas. However, in 4 examined healthy muscles the intensity of changes in EMG parameters correlating significantly with age seems to be related to the length of the muscles innervating them, and to the processes of ageing of the neuromuscular apparatus and blood vessels supplying it. Extensor muscle (EDB) innervated by motor neurons with longest axons may be the most sensitive indicator of the processes of ageing of peripheral motor neurons.