Electrodiagnostic Studies

Abstract

Electrodiagnostic studies include electromyography (EMG), electroneurography (ENG), and the study of late response. EMG is a diagnostic methodology that studies the electric activity of muscles. ENG (sensory and motor conduction studies) measures how fast the nerve conducts impulses. These studies are helpful in identifying and distinguishing muscle versus nerve disorders, mono- or multiple neuropathy versus polyneuropathy, and axonal neuropathy versus demyelinating neuropathy. The most important test in leprosy is electroneurography. Early leprosy neuropathy is characterized by ENG signs of mainly demyelinating damage, while late leprosy neuropathy produces different ENG signs in relation to the seriousness of the clinical picture and the sequelae of previous lesions. ENG confirms the diagnosis of neuropathy, and detects the affected nerve as well as early nerve involvement prior to clinical evidence. The localization of the lesion is necessary to facilitate further investigations such as echography and nuclear magnetic resonance or surgical interventions.