We hypothesize that segregation of mutations into the different EMG patterns depended on the underlying pathophysiological mechanisms. Results allow us to suggest EMG guidelines for the molecular diagnosis, which can be used in clinical practice.

SummaryLewis-Sumner syndrome (LSS) is a dysimmune peripheral nerve disorder, characterized by a predominantly distal, asymmetric weakness mostly affecting the upper limbs with sensory impairment, and by the presence of multifocal persistent conduction blocks. The nosological position of this neuropathy in relation to multifocal motor neuropathy (MMN) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is still debated. We report the clinical, biological and electrophysiological features, the course and the response to treatment in 23 LSS patients. The initial symptoms started in the distal part of an upper limb in 70% of patients. They were sensorimotor in 65% and purely sensory in 35% of patients. A cranial nerve involvement was observed in 26% of patients and a distal limb amyotrophy in 52%. The CSF protein level was normal in 67% of patients and mildly elevated in the remainder. None had serum anti-GM1 antibodies. There were multiple motor conduction blocks (average of 2.87/patient), predominantly located in the forearm, whereas demyelinating features outside the blocked nerves were rare. Abnormal distal sensory potentials were found in 87% of patients. The electrophysiological pattern suggests a very focal motor fibre demyelination sparing the nerve endings, whereas sensory fibre involvement was widespread. The course was chronic progressive in 71% ofpatientsand relapsing-remitting inthe others. During the follow-up study (median duration of 4 years), half of the patients progressed with a multifocal pattern and the distribution of the motor deficit remained similar to the initial presentation. The other patients showed a progression to the other limbs, suggesting a more diffuse process. Fifty-four percent of the patients treated with intravenous immunoglobulin showedanimprovement, compared with 33% of the patients treated with oral steroids. Overall, 73% of patients had a positive response to immune-mediated therapy. LSS may be distinguished from MMN by the presence of sensory involvement, the absence of serum anti-GM1 antibodies and, in some cases, a positive response to steroids. In some of the patients in our study, LSS evolved into a more diffuse neuropathy sharing similarities with CIDP. Others had a clinical course characterized by a striking multifocal neuropathy, which suggests underlying mechanisms different from CIDP. Overall, whatever the clinical course, LSS responded to immunemediated treatment in a manner similar to CIDP.Keywords: Lewis-Sumner syndrome; multifocal acquired demyelinating sensory and motor neuropathy; multifocal motor neuropathy; chronic inflammatory demyelinating polyradiculoneuropathy Abbreviations: CB = conduction block; CIDP = chronic inflammatory demyelinating polyradiculoneuropathy; CMAP = compound muscle action potential; CV = conduction velocity; DL = distal latency; IVIg = intravenous immunoglobulin LSS = Lewis-Sumner syndrome; MMN = multifocal motor neuropathy; SNAP = sensory nerve action potential

We retrospectively analyzed 146 patients fulfilling the European Federation of Neurological Societies and the Peripheral Nerve Society (EFNS/PNS) criteria for definite chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) to (1) evaluate the relevance of these criteria, (2) assess the frequency of CIDP variants, and (3) determine the response to treatment and the prognosis. We found that 75% of these patients fulfilled the main EFNS/PNS clinical and electrophysiological criteria (type I). The remaining patients were diagnosed using laboratory tools as supportive criteria. The common form of CIDP represented 51% of patients. We observed a high frequency of the sensory variant (35% of patients) and the rapid onset form (18%). A positive response to treatment was observed in 87% of patients, with a similar efficacy of prednisone and IVIg. However, in the long term, 40% of treated patients remained dependent on treatment. The IVIg dependency rate was higher than the prednisone or plasma exchange dependency rate (55%, 18%, and 23%, respectively; p = 0.0054). Severe handicap was observed in 24% of patients.

Objective: To determine whether rituximab 375 mg/m 2 was efficacious in patients with immunoglobulin M (IgM) anti-myelin-associated glycoprotein antibody demyelinating neuropathy (IgM anti-MAG demyelinating neuropathy).Methods: Fifty-four patients with IgM anti-MAG demyelinating neuropathy were enrolled in this randomized, double-blind, placebo-controlled trial. The inclusion criteria were inflammatory neuropathy cause and treatment (INCAT) sensory score (ISS) $4 and visual analog pain scale .4 or ataxia score $2. The primary outcome was mean change in ISS at 12 months.Results: Twenty-six patients were randomized to a group receiving 4 weekly infusions of 375 mg/m 2 rituximab, and 28 patients to placebo. Intention-to-treat analysis, with imputation of missing ISS values by the last observation carried forward method, showed a lack of mean change in ISS at 12 months, 1.0 6 2.7 in the rituximab group, and 1.0 6 2.8 in the placebo group. However, changes were observed, in per protocol analysis at 12 months, for the number of patients with an improvement of at least 2 points in the INCAT disability scale (p 5 0.027), the self-evaluation scale (p 5 0.016), and 2 subscores of the Short Form-36 questionnaire. Within the spectrum of chronic immune-mediated neuropathies, demyelinating neuropathy associated with immunoglobulin M (IgM) monoclonal gammopathy and antibodies against myelin-associated glycoprotein (MAG) is a distinct entity that typically presents with progressive sensory ataxia and painful paresthesias.1-8 Patients present with a striking immunochemical profile, suggesting the possibility of an autoimmune mechanism: monoclonal IgM recognizes a carbohydrate MAG epitope, which is shared with a number of other glycoconjugates involved in cell adhesion, including the Po glycoprotein of myelin, peripheral myelin protein-22, sulfated sphingolipid, and other related glycolipids.9,10 The disease may progress slowly over many years in some patients, whereas others develop significant disability mostly due to dysesthesias and ataxia; thus, there is a need to develop effective treatments.