Electrophysiology Testing of Movement Disorders

A battery of tools is used to provide neurophysiological characteristics of movement disorders, including EMG, EEG, EEG-EMG with back-averaging, evoked potentials, and long-latency EMG reflexes. Surface EMG forms the foundation of movement neurophysiology and can clarify muscle discharge timing and spatial relationships, as well as frequency information. This is useful for distinguishing tremor types, tremor versus myoclonus, and which muscles are involved in dystonia. Common modalities that are simultaneously recorded with EMG are EEG and motion detectors. Combined EMG with EEG recordings during myoclonus is useful for myoclonus classification and source localization. Evoked potentials and long-latency reflexes can assist with defining the myoclonus pathophysiology. These tests can distinguish between myoclonus of cortical versus subcortical origin, which affects treatment strategy decisions. EMG is useful for muscle localization for botulinum toxin injection. Chorea, tics, and psychogenic movement disorders mostly show nonspecific EMG patterns, limiting the usefulness of the technique in these situations.