The strategy of the electromyographic test of muscles is based on anatomic sampling. Each muscle examined represents a specific peripheral nerve, and usually several nerve roots. Based on the distribution of involved muscles, the examiner tries to infer the neurologic structure common to their innervation. This serves to localize the lesion. The following charts represent the innervation of the muscles of the upper and lower extremities. The myotomes are primarily based on clinical and pathologic information. An overview chart is presented first, followed by charts of one or two individual roots. The latter permit the examiner to select a group of muscles with a significant contribution from the indicated root. A major contribution is indicated by a capital X, and minor involvement by a lowercase x. Minimal involvement is signified by an x in parentheses. This same information is repeated in the second (newer) charts. The latter charts, however, include the electromyographic data, signified by capital O.
Keywords: electromyographic test; peripheral nerve; nerve roots; neurologic structure; innervations; myotomes; muscles
Chapter. 491 words. Illustrated.
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