Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a chronic and often disabling sensory motor neuropathy postulated as caused by an immune attack against peripheral nerve myelin. In addition to a classic sensory-motor polyneuropathy, other phenotypes of CIDP have been described including the Lewis-Sumner syndrome, distal acquired demyelinating symmetric (DADS) neuropathy, pure motor CIDP, pure sensory CIDP including chronic immune sensory polyradiculopathy (CISP), and focal CIDP. These phenotypes are currently considered to be variants of CIDP, even if the possibility that they represent different demyelinating neuropathies cannot be fully excluded also considering that there may be some differences in the response to therapy. The possible role of the immune system in the pathogenesis of CIDP is supported by sevarl data even if the precise targets and actors (antibodies and lymphocytes) of this immune response remain uncertain. More recently a small proportion of patients (up to 10%) was reported to have antintibodies, mostly of IgG4 isotype, against some proteins at the node of Ranvier inccludig contacti-1, neurofascin 155 and, less freferequently Neurofascin 155/186 and conontactin-associated protein 1 (Caspr1). Several immune therapies have been reported to be effective in CIDP including steroids, plasma exchange, high-dose intravenous immunoglobulin (IVIg), and more recently subcutaneous immunoglobulins (SCIg). It is therefore difficult for the clinician to decide when to start treatment in CIDP and what therapy to first use. This decision should consider the efficacy, cost and side effects of these therapies. A recent randomized controlled trial comparing the six-month efficacy of IVIg and intravenous methylprednisolone showed that IVIg were more frequently effective and tolerated than steroids during the first six month of treatment, although, when effective, steroids were less frequently associated with deterioration than IVIg after therapy discontinuation. Even if similarly effective to IVIg, plasma exchange is usually considered the third choice since it is more invasive for the patients and has an higher prevalence of side effects. A number of immunosuppressive agents have been also reported to be useful in CIDP even if their efficacy was not so far confirmed in randomized trials. SCIg were recently proved to be effective as maintenance therapy after improvement with IVIg.
Multifocal motor neuropathy (MMN) is a purely motor neuropathy characterized by the presence of multifocal partial motor conduction blocks, frequent association with anti-GM1 IgM antibodies and usually good response to therapy. The pathogenesis of MMN is still unknown but there is some evidence mostly based on the response to immune therapies and association with anti-glycolipids antibodies, that the disease is immune mediated. Antibodeis to the ganglioside GM1 are usually found in 40-50% of the patients even if their prevalence increases to 70-80% of MMN patients when GM1 is tested in addition to galactocereroside. Almost 80% of patients improve with IVIg whose efficacy was confirmed in five randomized controlled trials. IVIg induces a rapid improvement usually lasting a few weeks that needs to be maintained with periodic infusions for long period of time. The response to IVIg often declines however after several years concurrently with the progressive reduction of distal CMAP amplitude. SCIg were also shown to be effective in MMN as maintenance therapy after improvement with IVIg. Steroids and plasma exchange are usually ineffective in MMN and were sometime associated with clinical worsening. Other immune therapies have been used in MMN either as adjunctive therapy to reduce IVIg infusions or to treat non-responsive patients. High doses intravenous cyclophosphamide was reported to be effective in 50% of the patients but has relevant side effects. Occasional patients were reported to improve or stabilize with other immune suppressive agents but none of them proved to useful in randomized controlled studies so that their use should be only considered in MMN patients non responding to IVIg.
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