A Practical Guide to Identify Patients With Multifocal Motor Neuropathy, a Treatable Immune-Mediated Neuropathy

Multifocal motor neuropathy (MMN) is a rare immune-mediated motor neuropathy characterized by asymmetric weakness that preferentially affects distal upper limb muscles. The clinical features of MMN may be difficult to differentiate from motor neuron disease. Other conditions that may be mistaken for MMN include inclusion body myositis, chronic inflammatory demyelinating polyradiculoneuropathy, hereditary neuropathy with liability to pressure palsy, focal neuropathies, and radiculopathies. A key distinguishing electrophysiologic feature of MMN is the motor nerve conduction block located at noncompressible sites. MMN is a treatable neuropathy; therefore it is important that primary care physicians are aware of the features of the disease to identify potential patients and make referrals to a neuromuscular specialist in a timely manner. This review provides an overview of the disease, highlights key differential diagnoses, and describes available treatment options for patients with MMN.