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Role of electromyography in amyotrophic lateral sclerosis
Author(s) -
Behnia Mehrdad,
Kelly John J.
Publication year - 1991
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880141217
Subject(s) - amyotrophic lateral sclerosis , medicine , electromyography , denervation , compound muscle action potential , snap , physical examination , nerve conduction study , fibrillation , nerve conduction velocity , physical medicine and rehabilitation , cardiology , nerve conduction , surgery , electrophysiology , disease , atrial fibrillation , computer graphics (images) , computer science
Abstract We reviewed the role of electrodiagnostic testing in amyotrophic lateral sclerosis (ALS) in a large ALS clinic. Over 31 months, 133 patients with a clinical diagnosis of ALS were tested. In most, nerve conduction studies were normal, and needle electrode examination showed active denervation in the upper and lower limbs or the limbs and bulbar muscles (Lambert's criteria). However, 50 of 133 patients did not fulfill Lambert's criteria at presentation because of abnormal nerve conduction studies (11 patients), abnormal F‐wave latencies (6 patients), or insufficiently distributed fibrillation potentials (40 patients). This study reveals that a large proportion of patients with a clinical diagnosis of ALS fail to have classical findings on initial electrodiagnostic studies, and reveals several caveats of electrodiagnostic testing in these patients: (1) Conduction studies may be unreliable in motor nerves with markedly low compound muscle action potential (CMAP) amplitudes. (2) Sensory nerve action potential (SNAP) amplitudes may be abnormal in a small percentage of otherwise typical ALS patients. However, better controls for elderly subjects are needed. (3) Needle electrode examination may not show widespread active denervation early in the disease. (4) Some patients may have a mild polyneuropathy. (5) The classic diagnostic criteria may need to be modified to allow earlier acceptance of many ALS patients into therapeutic trials.