What is the role of antibody testing in the workup of multifocal motor neuropathy (MMN) with conduction block?

Updated: Nov 12, 2018
  • Author: Sasa Zivkovic, MD, PhD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Most studies report elevated titers of anti-GM1 antibodies in 50% of patients with multifocal motor neuropathy (MMN), but values and sensitivity depend on the methodology. Very high titers of anti-GM1 antibodies (>1:6400) have 80% specificity for MMN, but only 20-30% of patients with MMN have titers of 1:1800 and higher. Lower titers (1:400-800) are less specific and can be found with other neuropathies and amyotrophic lateral sclerosis (ALS).

Clinical features of MMN patients with high titers of anti-GM1 antibodies are typically indistinguishable from patients with negative titers.

The variable sensitivity of different methods of measuring anti-GM1 antibodies is well described. The highest yields and sensitivity of up to approximately 90% have been reported with covalent enzyme-linked immunosorbent assay (ELISA) methodology, while some commercially available assays for anti-GM1 antibodies may have sensitivity that is as low as 20-30%.

The sensitivity of testing may be further increased by adding anti-GM1/galactocerebroside antibodies, although this test may still not be available through commercial laboratories. [17]

Other autoantibodies

Various studies showed elevated titers of other antibodies in MMN including NS6S, neurofascin-186, and gliomedin antibodies. [18, 19] Clinical significance of these antibodies is still not well understood, and these assays are not widely comercially available.


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