Non-invasive approach of motor unit recording during muscle contractions in humans

Information about the structural and functional characteristics of the moto r unit (MU) is highly relevant for the diagnosis of neuromuscular disorders , Electromyography (EMG) is a suitable method for obtaining the information needed. The problem is the separation of the activity of one MU from other s which are simultaneously active. Such investigations of single MU activit y have commonly used invasive methods, e.g. employing a needle or a wire. C onventional surface-EMG methods have limited resolution and detect, at high contraction levels, multiple MU superimposed one on the other. The separat ion of the activity of a single MU can be achieved in a non-invasive way wh en highly specialised acquisition techniques are used. One approach, called high spatial resolution EMG (HSR-EMG), is based on the use of multi-electr ode arrays in combination with a two-dimensional Laplace filter. The HSR-EM G permits the completely non-invasive detection of single MU activity even during maximal voluntary contractions. First applications have shown that t he method provides a deeper insight into the functional and structural char acteristics of the MU. In this paper the application of HSR-EMG to the diag nosis of neuromuscular disorders will be presented, and the latest results will be given of its application in the evaluation of treatment of patients with plexus lesion.