Invited Review: Multifocal Motor Neuropathy: A Narrative Review-Article

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Multifocal Motor Neuropathy (MMN) is a rare, autoimmune polyneuropathy that primarily affects motor neurons, yet sparing the sensory ones. Predominantly manifesting in middle-aged males, MMN is characterized by asymmetric, progressive weakness, notably affecting the distal upper limbs. Occasionally, minor sensory issues may occur in the lower extremities. It is marked by specific motor conduction blocks, and electrodiagnostic criteria are crucial for its diagnosis, although criteria themselves remain debated for precision.<br /><br />Diagnostic testing shows that about 30-40% of MMN patients exhibit elevated anti-GM1 antibodies. Detection methods are evolving, attempting to capture more accurate serological evidence. Radiological assessments, particularly involving MRI and ultrasound, reveal nerve enlargements, but these findings aren't unique to MMN. Thus, differentiating MMN from other neuropathies—like Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) or Amyotrophic Lateral Sclerosis (ALS)—remains challenging, with nerve conduction studies being a pivotal part of the diagnostic process.<br /><br />Immunoglobulin therapy, primarily intravenous (IVIG) and subcutaneous (SCIG), is the mainstay treatment, offering symptomatic relief and temporary halting of disease progression. Yet, its long-term effectiveness wanes, calling for alternative or adjunctive therapies. Emerging evidence suggests complement inhibitors potentially as a future alternative therapy for MMN, targeting underlying pathogenic mechanisms.<br /><br />Despite treatment with IVIG, MMN patients continue to experience progressive muscle weakening over time. Hence, ongoing research emphasizes the need for earlier diagnosis, more effective and sustainable therapies, and a better understanding of the disease's pathophysiology to potentially offer lasting remission or even a cure. Comprehensive clinical frameworks and further trial findings may refine diagnostic accuracy and treatment efficacy in managing MMN.

Keywords

Multifocal Motor Neuropathy

autoimmune polyneuropathy

motor neurons

anti-GM1 antibodies

nerve conduction studies

ncs

IVIG therapy

complement inhibitors

diagnostic criteria

pathophysiology

treatment efficacy

nerve conduction studies

nerve conduction study

ncs