Is needle exam in nerve conduction studies useful in the diagnosis of Guillain-Barre syndrome (GBS)?

Updated: Jul 14, 2021
  • Author: Michael T Andary, MD, MS; Chief Editor: Milton J Klein, DO, MBA  more...
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The needle examination is of limited value in GBS. Reduced motor unit recruitment and absent denervation help to support the suggestion of a demyelinating mechanism, although the same changes can be observed in early axonal damage with pending wallerian degeneration. In severe cases, denervation changes may be observed later in the disease course.

In the axonal variant of the disease, absent or markedly reduced distal CMAP is observed on NCS. On needle examination, profuse and early denervation potentials (fibrillations) also support the conclusion that there has been axonal injury.

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