MRI of the brachial plexus in polyneuropathy associated with monoclonal gammopathy

On magnetic resonance (MR) imaging of the brachial plexus increased signal intensity and swelling of the brachial plexus has been found in chronic inf lammatory demyelinating polyneuropathy (CIDP). Whether these proximal abnor malities are also present in the distal polyneuropathy associated with mono clonal gammopathy is unknown. Therefore, we performed MR imaging of the bra chial plexus in 21 patients with polyneuropathy associated with IgM monoclo nal gammopathy (11 IgM with anti-MAG antibodies, 10 IgM without anti-MAG an tibodies). For comparison we studied 9 patients with polyneuropathy associa ted with IgG monoclonal gammopathy and 8 patients with CIDP. Among the 30 p atients with monoclonal gammopathy, 24 patients had demyelinating polyneuro pathy. Among these 24 patients, there was increased signal intensity of the brachial plexus on the T2-weighted images regardless of whether clinical d eficits were generalized or purely distal in location. No association was f ound with the isotype of the monoclonal gammopathy. Of the 8 patients with CIDP, 5 had brachial plexus abnormalities. None of the 6 patients with axon al polyneuropathy associated with monoclonal gammopathy had such abnormalit ies. Thus, MR imaging of the brachial plexus shows that the distal demyelin ating polyneuropathy associated with monoclonal gammopathy is more generali zed than presumed. (C) 2001 John Wiley & Sons, Inc.