[Clinical diagnosis of movement disorders--evoked potentials]

As a clinical diagnostic approach, the evoked potential has been used to differentiate movement disorders, especially myoclonic movements, Giant somatosensory evoked potentials (SEPs) and long-loop reflex to electrical stimulation of the peripheral nerve are commonly employed in the evaluation of patients with myoclonus. Recently, abnormality in a specific component of SEP frontal N30 has been reported in focal dystonia. Jerk locked back averaging has been applied to cortical reflex myoclonus, minipolymyoclonus, cortical tremor, simple tics, chorea-acanthocytosis, Huntington's chorea, etc. Silent period locked averaging is also used for asterixis. With these new electrophysiological techniques, evaluation of functional mechanisms in movement disorders may be expected, with fruitful results.