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Are multifocal motor neuropathy patients underdiagnosed? An epidemiological survey in Japan

Ai Miyashiro, Naoko Matsui, Yoshimitsu Shimatani

    Muscle & Nerve
    |April 18, 2014
    PubMed
    Abstract

    Insights

    Multifocal motor neuropathy (MMN) is diagnosed in approximately 1 in 20 amyotrophic lateral sclerosis (ALS) patients in Japan. Some centers may be underdiagnosing MMN, highlighting the need for increased awareness.

    Area of Science:

    • Neurology
    • Epidemiology

    Background:

    • Epidemiologic survey comparing multifocal motor neuropathy (MMN) and amyotrophic lateral sclerosis (ALS) patients in Japan.
    • Focus on the relative prevalence and diagnostic considerations for MMN versus ALS.

    Purpose of the Study:

    • To conduct an epidemiologic survey comparing MMN and ALS patients in Japan.
    • To estimate the prevalence of MMN in relation to ALS.

    Main Methods:

    • Retrospective study of 46 MMN and 1,051 ALS patients from 2005-2009.
    • Diagnosis based on European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) and revised El Escorial criteria.
    • Inclusion of intravenous immunoglobulin (IVIg) efficacy in MMN diagnosis.

    Main Results:

    • The MMN to ALS patient ratio varied by center, averaging 0.05.
    • Estimated prevalence: 0.29 MMN cases and 6.63 ALS cases per 100,000 population.

    Conclusions:

    • MMN occurs in approximately 5% of ALS cases in Japan.
    • Potential underdiagnosis of MMN in certain Japanese medical centers.

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