Use of QTRAC Technique to Measure Axonal Excitability in Anti-MAG Neuropathy (EXCIMAG)

The QTRAC method is an electrophysiological technique that assesses peripheral nerve axonal excitability, using computerized analysis of the muscular response of musculus abductor pollicis brevis, to series of electrical stimulations of the median nerve. Because of its high sensitivity to small changes in axonal excitability, QTRAC may help improve the follow-up of patients suffering from peripheral neuropathy caused by anti-myelin-associated-glycoprotein antibodies (anti-MAG neuropathy), as axonal excitability is early affected in this disease. The main aim of the study is to compare QTRAC results in anti-MAG neuropathy patients, with QTRAC results in healthy persons (matched for sex and age). A secondary aim is to determine whether or not the disease's clinical severity (measured by quantitative clinical scores) is correlated with the results of the QTRAC and could be predicted by a model based on the several parameters measured in the QTRAC exploration. 100 anti-MAG neuropathy patients will undergo a QTRAC exploration and a thorough neurological examination with clinical scoring. The results will be compared with data (matched by sex and age) from the reference database on healthy subjects, that is provided with the QTRAC software. The investigators expect to prove that QTRAC results are modified in anti-MAG neuropathy patients, and that the clinical severity of the disease can be predicted by a combination of QTRAC-measured parameters.

Peripheral Neuropathy Associated With Anti-myelin Associated Glycoprotein Antibodies (Anti-MAG Neuropathy)

Computerized analysis of the muscular response of musculus abductor pollicis brevis, to series of electrical stimulations of the median nerve

Clinometric assessment using RT-MRC, Martin vigirometer, RT-mISS, T25W, 9 hole peg test, and ataxia scale

the duration of the refractory period of the median nerve (expressed in milliseconds) is automatically measured by the QTRAC system, using a series of double electrical stimulations (the first being supra-maximal and the second, sub-maximal) and progressively increasing the time between the two stimuli.

Inclusion Criteria: Anti-MAG neuropathy (peripheral neuropathy and IgM monoclonal gammopathy with anti-MAG activity superior to 1000 BTU) Exclusion Criteria: current treatment with a medication that modifies peripheral nerve excitability (e.g. anticonvulsivants)