Abstract

Previous issues of The Guides Newsletter have presented overviews of electrodiagnostic evaluation, including electromyography, nerve conduction studies, and somatosensory-evoked responses. This article contains suggestions for nonelectromyographers who read reports and identify questionable uses of electrodiagnosis, specifically for the evaluation of radiculopathy and focal neuropathy (eg, nerve entrapments), the two most common presentations. Some subtle abnormalities (eg, changes in motor unit recruitment pattern, changes in firing rate, or reduction in motor units recruited) often are overinterpreted by poorly trained or inexperienced electromyographers. Nerve conduction studies often are overused and may accompany the electromyogram without apparent indication, but they are nearly useless in diagnosing radiculopathy and should be included only for nerve entrapment or differential diagnosis of plexus injury. Nerve conduction studies often are accompanied by F waves and H reflexes. The F wave helps assess proximal portions of nerves and is used primarily in the diagnosis of Landry-Guillain-Barré syndrome but has poor sensitivity and specificity in evaluation of radiculopathy or entrapment neuropathy. The H reflex is used primarily in S1 radiculopathy evaluation. The article includes six questions a clinician should bear in mind while interpreting the electrodiagnostic report. Improperly trained physicians may report false positive or negative results, so examiners should be aware of the qualifications of physicians to whom they refer their patients.

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