Nerve conduction studies and their clinical applications

Abstract

Nerve conduction studies provide the most sensitive and accurate account of peripheral neuropathophysiology. Though nerve conduction studies should never be performed in lieu of a clinical examination, the electrodiagnostic evaluation provides an optimal adjuvant to the clinical examination. Indications for nerve conduction studies are many, including evaluation of the nature of the pathophysiology, quantification of the severity of involvement, detection of the level of a neurologic deficit, and determining prognosis. Among other indications, limitations of the study should also be acknowledged, such as its confined evaluation of large myelinated peripheral nerve fibers. It should be understood that nerve conduction studies are conventionally performed with EMG studies, typically performed consecutively in order to provide a comprehensive evaluation of suspected neuromuscular impairment. It is imperative to emphasize that utilization of nerve conduction findings is limited and potentially misdirected without a thorough knowledge of peripheral neuropathophysiology and related conditions. Parameters by which the studies are evaluated are outlined in detail within this article and discussed in terms of clinical and neurophysiological significance. Reference tables are provided on the normal values of individual peripheral nerves, as established by various investigators. Nerve conduction findings and their clinical significance relative to various pathophysiological conditions are reviewed. Radiculopathies, lesions of the lumbosacral plexus, polyneuropathies, as well as mononeuropathy multiplex and simplex, are also discussed relative to their various etiologies, and respective forms of pathogenesis. Finally, nerve conduction studies may be effectively used to select the most beneficial therapy. Appropriate consultative referral is addressed with regard to primary pathologic conditions requiring neurosurgical, neurologic, rheumatologic, and immunologic care, among other disciplines relative to the underlying pathologic process. Local therapy may invariably be gauged in terms of various modes of medical, orthopedic, and surgical intervention, depending on the degree, nature, and distribution of involvement of the neuropathy, as ultimately determined by the nerve conduction studies. In conclusion, nerve conduction studies provide a reliable index of measurement in the diagnosis, treatment, and prognosis of the patient.