The aim of this study is to establish an experimental system for scanning electromyography (EMG) to visualize the electrical activity of the motor unit (MU) territory in investigating the alterations in MU size in Juvenile Myoclonic Epilepsy (JME). MU is the basic unit of the skeletal muscle. Conventional EMG has already been used in routine clinical examinations to diagnose neuromuscular diseases. It provides information in terms of the amplitude and the duration. It reflects only a limited part of the MU. Scanning EMG method gives temporal and spatial information about the MU providing a map for the entire motor unit. An experimental system consisting of an EMG instrument, an actuator, a data acquisition system and a notebook for scanning EMG was designed and set up. The measurements are achieved by two concentric needle electrodes (CNE). An M-File in MATLAB 7.2 is used to construct 3-D plots of the MU territory. Measurements have been performed with seven JME patients and two healthy volunteers. The genetic origin of the JME suggested the subclinical anterior horn cell involvement in JME. Some evidences were found on the preponderance of the normal 'large' MUs using several electrophysiological methods. Scanning EMG system is used to confirm the presence of these large MUs. 3-D maps of the MU territories are constructed using the data acquired from the subjects. It has been demonstrated that the experimental system can be used to examine the motor unit territory different groups of diseases for clinical studies. This study will be extended to ten JME and to ten healthy volunteers, and by including three spinal muscular atrophy cases (SMA)
