Chronic inflammatory demyelinating polyneuropathy (CIDP) is a slowly progressive disabling neuropathy characterized by subacute onset of muscle weakness, distal sensory deficit, elevated spinal fluid protein, and slow nerve conduction velocity with or without conduction block. A monoclonal gammopathy is at times present in the serum of some patients. Because immune-mediated mechanisms against peripheral nerve myelin are thought to be primarily responsible for the clinical manifestations of CIDP, the treatment of choice is with corticosteroids, plasmapheresis or immunosuppressive drugs. Although many patients initially respond to these agents, a large number of them become resistant or develop unacceptable side effects that necessitate their discontinuation. The need for a more effective and safe immunotherapy in CIDP patients prompted the present study using high-dose intravenous immunoglobulin (IVIg). IVIg is an immunomodulating agent which has been recently shown to be effective and safe in the treatment of a number of patients with immune-related neuromuscular diseases.

This is a double blind, randomized, placebo controlled, trial involving 60 patients, half of which will receive IVIg and the other half placebo (D5/W). Because IVIg is prohibitively expensive, a controlled trial is needed to provide convincing evidence of efficacy, and ensure that the benefit is not due to spontaneous improvement or to observer bias. The dose of IVIg is 2 GM/Kg divided into two daily doses administered monthly for six months. The drug will be considered effective if patients experience an increase of more than 25% in their baseline muscle strength. Muscle strength will be assessed with a series of objective dynamometric measurements performed before and after each monthly infusion.