Recent progress in the diagnostic use of surface EMG for neurological diseases

The different techniques to measure and analyze surface EMG are summarized with an emphasis on the clinician's point of view. The application of surfa ce EMG in neurological disease is hampered by many inherent problems, espec ially the difficulties in extracting features of single motor units. Howeve r, the evolution of surface EMG from single bipolar recordings via a linear array of multiple electrodes to densely packed, multi-channel electrode ar rays could in principle solve this problem. The added value of using multip le channels (up to 128) with an interelectrode distance of a few millimetre s to obtain more spatial information is emphasized. At least for some muscl es it is now possible to extract information from the surface EMG, conventi onally thought to belong to the domain of needle EMG (for example the "elec trical size" of motor units). The use of analysis techniques such as the es timation of muscle fiber conduction velocity has already proven to be of di agnostic value in several myopathies characterized by a disturbed membrane function and in metabolic myopathies with abnormal fatigue profiles. Future research should be directed at the development of analysis techniques enab ling the extraction of more relevant motor unit variables from surface EMG signals. (C) 2000 Elsevier Science Ltd. All rights reserved.