Temporal evolution of nerve conduction study abnormalities in anti‐myelin‐associated glycoprotein neuropathy

Abstract

Background A distal‐predominant demyelinating symmetric pattern is most frequent in patients with neuropathy associated with anti‐myelin‐associated glycoprotein (MAG) antibodies. The literature however lacks longitudinal data to describe whether this is consistent over time. Methods From the Ottawa Neuromuscular Center database, we identified 23 patients with both immunoglobulin M gammopathy and anti‐MAG antibodies. For median, ulnar and fibular motor conduction studies, we analyzed distal latency and amplitude, negative peak duration, terminal latency index (TLI), and conduction velocity. For median, ulnar, sural, and superficial fibular sensory conduction studies, we analyzed distal latency and amplitude. Results were compared for the earliest and the latest data sets. Results The mean time interval between the two assessment points was 6.5 years. Median and ulnar motor nerve conduction studies did not show a significant change for any of the parameters tested. There was disproportionate prolongation of median distal motor latency and reduction in TLI, compared to the ulnar nerve. Deep fibular motor conduction studies showed a marked reduction in amplitudes over time. Sensory potentials were recordable in the upper limb in less than 50% at the first study and less than 25% on the most recent study. There was an even larger attrition of recordable sural and superficial fibular sensory potentials. Conclusions Our results highlight the stability of median and ulnar motor conduction study results over a mean observation period of 6.5 years. In contrast, lower limb motor and all sensory potentials show a marked trend toward becoming unrecordable.

Efficacy of rituximab in anti‐myelin‐associated glycoprotein demyelinating polyneuropathy: Clinical, hematological and neurophysiological correlations during 2 years of follow‐up

“…Although Bourque et al recently reported a marked trend towards lower limb motor and sensory potentials becoming unrecordable [44], we did not observe any worsening, but stabilization of these values. The change in SNAP amplitude in the sural nerve, even if only partially significant, seem to be in line with other findings.…”

Antibody testing in neuropathy associated with anti-Myelin-Associated Glycoprotein antibodies: where we are after 40 years

“…MAG neuropathy can present with mild clinical deficit, and remain stable or only slowly progressive for many years, but can then enter a more rapidly progressive course that can lead to disability, probably resulting from cumulative nerve damage [14,15 ▪ ,16]. There is no correlation between antibody titers and severity of the neuropathy, although increasing antibody titers are probably indicative of expansion of the monoclonal gammopathy.…”

Anti-MAG neuropathy: historical aspects, clinical-pathological correlations, and considerations for future therapeutical trials

“…Disability is more closely correlated with a reduction of CMAP amplitudes indicative of axonal loss. 43 The lower limb motor and sensory potentials show a marked trend to become unexcitable over time, 45 so that the studies may not meet EFNS/PNS demyelinating criteria, with the percentage of patients meeting the criteria reported as ranging from 20.9 to 91%. 29 30 42 45 In the study reporting 20.9% however, at least 1 nerve in all patients showed demyelinating range abnormalities.…”