Different patterns of sensory nerve involvement in chronic inflammatory demyelinating polyneuropathy subtypes

Abstract

Introduction/Aims: Among subtypes of chronic inflammatory demyelinating polyneuropathy (CIDP), different immune pathophysiologies have been proposed. In this study, sensory nerve conduction studies were compared among clinical subtypes to attempt to better understand the underlying pathophysiology. Methods: A total of 138 patients with CIDP was classified into clinical subtypes: typical CIDP (N = 68), multifocal CIDP (N = 27), or other (N = 2). Patients with immunoglobulin M (IgM) neuropathy anti-myelin-associated glycoprotein neuropathy (MAG; N = 19) were also included as disease controls. Sensory nerve action potentials (SNAPs) were recorded in the median, ulnar, and superficial radial and sural nerves.Results: SNAP amplitudes (P < .05) and conduction velocities (P < .01) in the median nerve and conduction velocities (P < .05) in the ulnar nerve were lower in typical CIDP than in multifocal CIDP, whereas those in the radial and sural nerves were comparable in each group. Low median and normal sural SNAP amplitudes were more common in typical CIDP (P < .005) than in multifocal CIDP, suggesting predominant involvement at terminal portions of the nerves.Discussion: Terminal portions of sensory nerves are preferentially affected in typical CIDP compared with multifocal CIDP. These findings might be partially explained by the hypothesis of antibody-mediated demyelination in typical CIDP at the regions where the blood-nerve barrier is anatomically deficient, whereas multifocal CIDP predominantly affects the nerve trunks, largely due to cell-mediated demyelination, with disruption of the blood-nerve barrier.

Electrophysiology to identify disease mechanisms in CIDP: Reliability and value

“…11 Third, the electrophysiological findings in the current study of sensory conductions, may, according to the authors, be due to myelin thickness variation and vulnerability at entrapment sites. 7 However, this is not supported by previous analyses which failed to show demyelination at entrapment sites in CIDP, 12 as opposed to the findings in anti-MAG neuropathy. 13 If an antibody-mediated process were predominant in typical CIDP, similar to that in anti-MAG neuropathy, slowing in the same nerve segments may have been expected.…”

“…Furthermore, published data on treatment response in multifocal CIDP has been heterogeneous and contradictory, some favoring steroids, 5 others describing deterioration on steroids, 10 and still others favoring immunoglobulins, 4 or not 11 . Third, the electrophysiological findings in the current study of sensory conductions, may, according to the authors, be due to myelin thickness variation and vulnerability at entrapment sites 7 . However, this is not supported by previous analyses which failed to show demyelination at entrapment sites in CIDP, 12 as opposed to the findings in anti‐MAG neuropathy 13 .…”

“…We have ourselves found the Overall Neuropathy Limitation Scale 8 (a more sensitive tool than the HDS for chronic dysimmune neuropathy), of little value in this setting and routinely use the Rasch‐built Overall Disability Scale for multifocal motor neuropathy (MMN‐RODS), 9 which is more adapted to the deficits in multifocal CIDP (unpublished data). As such, it is therefore difficult to conclude that there is similar efficacy of steroids but poorer efficacy of immunoglobulins and plasma exchange in multifocal CIDP than in typical CIDP, as described in their first study, 5 and as cited in the current discussion 7 . Furthermore, published data on treatment response in multifocal CIDP has been heterogeneous and contradictory, some favoring steroids, 5 others describing deterioration on steroids, 10 and still others favoring immunoglobulins, 4 or not 11 .…”

“…In the current issue of the journal, the same group from Chiba, Japan, describes the findings of a further electrophysiological analysis, exploring exclusively sensory conduction studies in a cohort of 138 patients meeting the recently updated European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) guidelines for CIDP. 7 Sixtyeight subjects had a typical form and 27 a multifocal form. Nineteen subjects with anti-MAG neuropathy were included as disease controls.…”

“…As such, it is therefore difficult to conclude that there is similar efficacy of steroids but poorer efficacy of immunoglobulins and plasma exchange in multifocal CIDP than in typical CIDP, as described in their first study, 5 and as cited in the current discussion. 7 Furthermore, published data on treatment response in multifocal CIDP has been heterogeneous and contradictory, some favoring steroids, 5 others describing deterioration on steroids, 10 and still others favoring immunoglobulins, 4 or not. 11 Third, the electrophysiological findings in the current study of sensory conductions, may, according to the authors, be due to myelin thickness variation and vulnerability at entrapment sites.…”