Cardinal Rules of EMG 3: When in Doubt, Re-Examine the Patient

J Korean Assoc EMG Electrodiagn Med 2003;5(2):134-140.
Published online May 10, 2003.

Abstract

The Electrodiagnostic (EDX) studies must be planned according to the clinical context. Every EDX evaluation should begin with a brief history and directed physical examination. The EDX evaluation should maintain a proper balance between collecting the necessary data to answer the clinical question and minimizing patient discomfort. Sufficient nerve conduction studies (NCSs) and needle electromyography (EMG) can usually be performed within 1.0 1.5 hours to arrive at an accurate electrophysiologic diagnosis. Electromyographer should begin the study with the area of most interest. By planning ahead and considering which NCS should be performed first and which muscle should be sampled on needle EMG, an accurate diagnosis may be reached in many patients, even when only few NCSs or muscles are examined. The EDX studies may identify minor abnormalities that may suggest subclinical disease or may be irrelevant. Clinically insignificant findings occur partly because of the wide range of normal values. A diagnosis based on minor EDX abnormalities that do not correlate with the clinical manifestations may be hazardous. An unexpected abnormal finding on NCS or needle EMG that does not fit the clinical examination should always raise the possibility of a technical problem. One can usually be certain of a diagnosis only when the clinical findings, NCSs, and needle EMG abnormalities all correlate well.

Key Words: History, Physical examination, EDX, EMG, NCS