Surface EMG Examination of Amyotrophic Lateral Sclerosis

Electromyogram signals were recorded and analyzed from subjects with Amyotrophic Lateral Sclerosis. In contrast to routine needle clinical examinations, we used surface electrodes (High Density surface EMG, HDsEMG) in an attempt to show the feasibility of muscle assessment using a non-invasive approach. The study started by examining Fasciculation Potentials, a crucial electrodiagnostic feature of ALS. The feasibility of the proposed surface recording for their detection was soon established, so the fasciculation potentials were then further explored in order to understand the nature of their spontaneous discharges, when compared with regular motor unit discharges.. Due to a lack of software applications to analyze the signals from HDsEMG electrodes, a number of new techniques were designed and implemented to extract these potentials from raw EMG, and to classify them based on their shapes. Taking advantage of advanced multi-channel recording technologies, we explored Fasciculation Potentials with respect to the ‘Innervation Zones’ of their sites of origin, where signs of muscle reorganization were observed. In addition to their non-invasive nature and their comfort for the patients, HDsEMGs were proposed as potentially more suitable in monitoring the progress of the disease. Preliminary results were presented on this theme. Muscle functional capacity was also assessed, by measuring the slope of the EMG-force relation. Abnormal EMG-force slopes in some of the ALS subjects were recorded. In addition to global EMG analysis, single motor units were also extracted in a collaborative project which provided EMG decomposition outcome. We studied discharge behavior of single motor units in hand muscles of ALS subjects, during isometric voluntary contractions. Overall, we concluded that HDsEMG can substitute for many electrodiagnostic practices in clinics, and can provide supplementary information about the muscle which is not attainable using single needle recording.