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Multifocal Motor Neuropathy — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularMultifocal Motor NeuropathySCE Neurology

A 58-year-old woman presents with progressive asymmetric weakness and wasting affecting the left hand intrinsic muscles. NCS show motor conduction block at non-entrapment sites in multiple nerves. Sensory studies are normal. Anti-GM1 IgM antibodies are positive. What is the diagnosis?

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Correct answer: D — Multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is characterised by asymmetric, predominantly distal motor weakness without sensory involvement, conduction block in motor nerves at non-entrapment sites, and anti-GM1 IgM antibodies (present in ~50% of cases). It is important to distinguish from ALS as MMN is treatable. A: ALS does not have conduction block and has UMN signs. B: CIDP affects both motor and sensory nerves. D: Hereditary motor neuropathies do not show conduction block. E: IBM is a myopathy with characteristic pattern of weakness.

Reference: EAN/PNS MMN Guidelines (2010)