How to Interpret Needle EMG Study

Needle EMG is performed after nerve conduction studies (NCSs) to further localize various diseases from anterior horn cell to muscles.This Teaching Neurovisual is a visual aid to be used for teaching the interpretation of EMGs to medical students and neurology residents.Step 1 is the evaluation of spontaneous activity (muscle at rest) (Figure 1).Step 2 is the study of the motor unit action potentials (muscle contracted).Step 3 involves identification of patterns and localization, with the conjunction with NCS (Figure 2).Step 4 is the identification of the time course to better characterize the abnormalities previously seen.1,2