Differentiating Multifocal Motor Neuropathy from Entrapment Neuropathy—A Diagnostic Challenge

TOUCH MEDICAL MEDIA 17 Multifocal motor neuropathy (MMN) is a rare, immune-mediated neuromuscular condition characterized by impairment of the peripheral motor nerves, leading to muscle weakness, affecting the arms more than the legs. The disease was formerly known as MMN with conduction block (MMNCB), since a predominant feature is CB at multiple sites along the motor nerves, although at early stages the axons are not affected. Entrapment neuropathy (EN) occurs when single nerves in various body locations become chronically compressed or mechanically injured as a result of various factors, including anatomical structures, fibro-osseous tunnels, ligaments, local edema, tumors, diabetes, medications, arthritis, hypothyroidism, obesity, or repetitive movements. Nerve compression causes sensory symptoms, such as paresthesias, numbness, dysesthesias, muscle weakness, and atrophy (if untreated), in the affected anatomical area. The involvement of a single or more than one nerve can resemble some of the motor symptoms of MMN, and consequently, in its early stages, it is possible to confuse the two conditions, which can have serious clinical consequences.