However, needle electrode evaluation is not usually useful until 3 weeks after an injury, when active denervation features may become apparent, so if a single study is requested, it should be done 3 weeks after the onset of neurologic deficits.Ĭarpal tunnel syndrome is one of the most common peripheral nerve disorders and can cause significant pain and dysfunction. A repeat study at least 10 days after the injury is usually necessary to assess for maximal deterioration of sensory and motor responses, at which time wallerian degeneration should be complete, and a response from distal stimulation will be absent with complete axonal injuries. Nerve conduction studies may be useful during the acute phase of an injury (within the first 24–72 hours) if nerve trunk stimulation can be performed above and below the lesion site to assess for conduction block or discontinuity.

Electrodiagnosis can assess nerve continuity, injury severity, and prognosis, which may be especially helpful if peripheral nerve surgery is being considered. Peripheral nerves may be injured by blunt or penetrating trauma, stretch injury, and secondary ischemia (eg, from compartment syndrome). This article reviews common indications for these tests, their limitations, and how to interpret the results, focusing on how they may best contribute to patient evaluation. Electrodiagnostic testing helps to precisely locate disease processes affecting the peripheral nervous system (including peripheral nerves, neuromuscular junctions, and muscles) and has limited use in the evaluation of central nervous system disorders.Įlectrodiagnostic studies can help establish if a patient is likely to have a muscle disease, a disorder of neuromuscular junction transmission, axon loss, or a demyelinating disease.Įlectrodiagnostic testing should be done by physicians who have appropriate training in it, as there are potential pitfalls in performing and interpreting the studies.Įlectrodiagnostic testing (traditionally but less accurately called electromyography) consists of 2 distinct but related procedures typically performed together to interrogate the peripheral nervous system: nerve conduction studies and needle electrode examination.

Nerve conduction test on lower back