What is the role of electrodiagnostic testing in the workup of brachial neuritis (BN)?

Updated: Oct 13, 2020
  • Author: Nigel L Ashworth, MBChB, MSc, FRCPC; Chief Editor: Milton J Klein, DO, MBA  more...
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  • Electrodiagnosis [12, 40, 41, 7, 42]

    • Electrodiagnosis should be considered initially to confirm neuropathic diagnosis and to rule out various other conditions (eg, radiculopathy, neuropathy, amyotrophic lateral sclerosis).

    • Specific localization can be made to various nerves.

    • Loss of sensory and motor amplitudes with relatively normal conduction velocity is frequent. Note, however, that this finding only begins to fall beyond the reference range after approximately 1 week.

    • Somatosensory evoked responses are not reliable for distinguishing radiculopathy from brachial plexus neuropathy, and F-waves are generally less helpful than routine conduction studies in localization.

    • Needle electromyogram (EMG) shows denervation (fibrillations, positive sharp waves, and/or motor unit potential changes) in affected muscles 2-3 weeks after onset; however, clinically uninvolved muscles also may show abnormalities. Approximately 50% of patients with unilateral clinical involvement demonstrate bilateral EMG abnormalities. EMG results for the paraspinal muscles usually are within the reference range. Electromyographic exclusion of a radiculopathy may be challenging. In addition, strict anatomic localization often is difficult.

    • Proximal conduction block has been reported in brachial neuritis; however, this finding should suggest focal forms of inflammatory demyelinating diseases. Proximal slowing also may occur from loss of large fibers, regenerating fibers, and/or segmental demyelination.

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