Electrodiagnostic patterns in MGUS neuropathy.

Monoclonal gammopathies of undetermined significance (MGUS) are frequently associated with neuropathies, particularly in the elderly. To better characterize the electrodiagnostic findings in MGUS-associated neuropathies, we analyzed electrodiagnostic data from 35 patients with MGUS-associated neuropathies (mean age 70.6; 12 IgM, 19 IgG, 4 IgA) who had no other cause for their neuropathies. Data was also analyzed for 29 age-matched patients (mean age 69.8) with diabetic neuropathies. Using electrodiagnostic criteria, studies were classified as being consistent with demyelination; 9 patients had findings consistent with axonal injury; and, in 3 patients, criteria for both demyelination and axonal injury were present. However, 24 of the 35 patients with MGUS-associated neuropathies had dyssummetric findings. In contrast, only 4 of the 29 patients with only diabetes had a dyssymmetric process (p < 0.0001). In MGUS-associated neuropathies, dyssymmetry is the most common, definable abnormal electrodiagnostic pattern.