Electrophysiological Techniques for Motor Unit Number Estimation

Various neurological diseases involving motor neurons damage lead to a decrease in the number of functioning motor units (MUs). Accurate estimation of the number of intact MUs plays significant role in evaluating motor neuron death. Quantitative analysis of MUs by methods of routine electromyography is usually not possible. Therefore, electrophysiological techniques for MU number estimation (so-called motor unit number estimation, MUNE), have been rapidly developing over the past decades. The first article on MUNE was published in 1971. Promising, accurate, and less time-consuming modifications have been developed since, and new methods for counting MU have been proposed. In recent years, one can see increasing interest in MUNE explained by the ongoing research on new possibilities of motor neuron disease treatment, and evaluation of their effectiveness, dynamic control of the disease. Today, MUNE is considered to be a potential biomarker in many clinical trials involving patients with motor neuron disease. This review provides in sights on available MUNE techniques, describes their comparative characteristics, advantages and disadvantages of each method and their application perspectives.