Abstract

INTRODUCTION

During the 1980s, patients were reported with a slowly evolving asymmetrical motor syndrome, often initially affecting the distal upper limbs. These patients were viewed as distinct from either spinal muscular atrophy or more typical chronic inflammatory neuropathies by the presence on clinical electrophysiological testing of very focal areas of conduction block in the motor fibres of peripheral nerves, with sparing of sensory fibres in the same nerve segments. It was subsequently demonstrated, first of all in case reports and then in larger series of patients, that a proportion of these cases had serum IgM antibodies to GM1 ganglioside. Thus the syndrome of multifocal motor neuropathy with conduction block (MMN) was born. Since then, the literature on this uncommon disease has grown considerably, particular highlights being its frequent and dramatic response to infusions with intravenous immunoglobulin (IVIg), its pathophysiological basis, and its nosological relationship with similar clinical syndromes (Nobile-Orazio 2001).