Length dependence in polyneuropathy associated with IgM gammopathy
Article first published online: 25 JAN 2006
Copyright © 2006 American Neurological Association
Annals of Neurology
Volume 59, Issue 2, pages 365–371, February 2006
How to Cite
Franssen, H. and Notermans, N. C. (2006), Length dependence in polyneuropathy associated with IgM gammopathy. Ann Neurol., 59: 365–371. doi: 10.1002/ana.20785
- Issue published online: 25 JAN 2006
- Article first published online: 25 JAN 2006
- Manuscript Accepted: 21 NOV 2005
- Manuscript Revised: 3 NOV 2005
- Manuscript Received: 16 AUG 2005
In polyneuropathy associated with monoclonal IgM gammopathy, nerve conduction studies may show disproportionate distal slowing consistent with segmental demyelination. This was suggested to represent a length-dependent demyelinating process, starting in distal and proceeding to proximal segments. Because the evidence for this is incomplete, we assessed whether length dependence occurs in IgM neuropathy.
In 22 patients with IgM neuropathy, 20 disease controls with chronic inflammatory demyelinating polyneuropathy (CIDP) and 36 normal controls, we investigated motor conduction, sensory conduction, and needle electromyography for nerves with short, intermediate-length, and long axons as well as conduction in short segments of the ulnar nerve from proximal to distal. To compare variables in nerves of different length, we normalized individual values with respect to the median in normal controls.
In IgM neuropathy, distal slowing and features of axon loss increased with nerve length, and ulnar nerve conduction became gradually slower from proximal to distal when the elbow segment was excluded. In CIDP, no clear length dependence was found except for distal amplitude.
The disproportionate distal slowing in IgM neuropathy may be part of a length-dependent process, assuming that this process is randomly distributed due to a generalized exposure to IgM. Ann Neurol 2006;59:365–371