[Changes of motor innervation in myasthenic muscles in relation to age (author's transl)]

The motor innervation in muscle biopsies from 45 myasthenic patients was studied by intravital staining with methylene blue. The enzymatic pattern and fibre type distribution was analysed in 12 cases. Quantitative data including the proportion of elongated motor endings and the terminal innervation ratio (TIR) of motor axons, were compared to histochemical data and to clinical data including age of patients. The incidence of elongated motor endings tends to be greater in younger patients, whereas an increased collateral ramification of motor axons occurs only after the age of 50. Small type III fibers suggesting denervation are also found in elderly patients only. The significance of these morphological differences in relation to age is discussed.