Neuropathie motrice multifocale avec blocs de conduction persistants

Multifocal motor neuropathy

PURPOSE OF REVIEW

Multifocal motor neuropathy (MMN) remains a difficult issue for neurologists, as its clinical and electrophysiological presentation may be atypical, and because no alternative treatment to periodic immunoglobulin infusions has been assessed in its long-term management. This review intends to summarize the most recent advances in the diagnosis and treatment of MMN.

RECENT FINDINGS

Recent reports have focused on atypical onset and unusual clinical presentation. Several sophisticated electrophysiological techniques, as triple stimulation, may help establish the presence of conduction blocks, as well as MRI findings. A recent immunological study focused on the detection of serum IgM binding to NS6S heparin disaccharide. In another research article, it was proposed that the use of combinatorial glycoarray or ELISA may increase the diagnostic sensitivity of antiglycolipid antibody testing. Subcutaneous immunoglobulin may represent an interesting alternative option to intravenous immunoglobulin. Lastly, recently reported open-label clinical trials with complement inhibitors and anti-CD20 monoclonal antibody may constitute a first step for further developments.

SUMMARY

Diagnostic criteria for MMN are well established, but challenging situations still occur. Progresses in neurophysiologic and other laboratory tests may help in clarifying doubtful diagnoses. Current research into the pathophysiology of MMN is required to determine the future treatment targets.

Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a chronic immune-mediated neuropathy that is particular for its asymmetric, multifocal, purely motor clinical presentation, often related to the distribution of individual nerves. Upper limbs are usually primarily and more severely affected, but lower limbs may be involved during the course of the disease. The hallmark of the disease is the presence, in electrophysiological studies, of persistent conduction blocks in the affected motor nerves, located outside the usual sites of nerve compression, contrasting with normal sensory nerve conduction velocities. The most typical laboratory finding is the presence of high levels of serum IgM antibodies to the ganglioside GM1, and less frequently to asialo-GM1, GD1a or GM2. These striking features may help distinguishing this neuropathy from both motor neuron disease and other chronic immune-mediated neuropathies. Several randomized controlled trials (RCT) have established the efficacy of high-dose intravenous immunoglobulin (IVIg), as well as subcutaneous immunoglobulin (SCIg). However, this therapy has a short-lasting effect, and need to be maintained with periodic infusions. This disappointing status has led to the search of other immune therapies whose efficacy has not been so far confirmed in RCT. This review intends to summarize current contents in the diagnosis and the treatment of MMN.

Efficacy of Intravenous Immunoglobulin in Multifocal Motor Neuropathy

Multifocal motor neuropathy is a distinct entity, whose treatment differs from that of other chronic immune-mediated neuropathies, mainly chronic inflammatory demyelinating polyradiculoneuropathy, and its variant, multifocal acquired demyelinating sensory and motor neuropathy, although they share some electrophysiological characteristics. From the first descriptions, intravenous immunoglobulins (IVIg) have been considered to be the gold standard of treatment for multifocal motor neuropathy. However, if the effectiveness of IVIg has been confirmed by several randomized, double-blind, placebo-controlled trials, only a few patients experience persistent improvement after a single or few courses of therapy, and the long-term efficacy of IVIg in this disease is currently debated. Consequently, there is a need for new therapeutic strategies that focus on the effects and the costs of this therapy over long-term follow-up.

Plasma exchange for systemic lupus erythematosus

Efficacy of plasma exchange in patients with systemic lupus erythematosus has not been supported by the results of the first non-controlled and retrospective studies. Nonetheless, they remain relevant for some selected patients with life-threatening manifestations and/or severe therapy-resistant manifestations. They can be used as an adjuvant therapy in combination with corticosteroids and, when required, other immunosuppressant(s) for refractory renal disease, alveolar hemorrhage, some neuropsychiatric manifestations, thrombotic thrombocytopenic purpura, catastrophic antiphospholipid syndrome, hyperviscosity syndrome or symptomatic cryoglobulinemia. The use of newer technologies, like immunoadsorption, possibly in combination with recent biologics, might, in the future, offer some new perspectives for extracorporeal therapy of systemic lupus erythematosus.