From the Research
Multifocal Motor Neuropathy (MMN) with conduction block is a distinct clinical entity that differs from Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) in its purely motor involvement, asymmetric weakness, and presence of conduction blocks in motor nerves. The key characteristics of MMN include progressive, asymmetric muscle weakness and atrophy without sensory involvement, primarily affecting distal upper limb muscles, and distinguished by the presence of conduction blocks in motor nerves on electrodiagnostic testing 1. In contrast, CIDP typically presents with symmetric weakness affecting both proximal and distal muscles, and importantly includes sensory symptoms like numbness and tingling, affecting both motor and sensory nerves 2. Treatment approaches also differ, with MMN responding well to intravenous immunoglobulin (IVIG) at doses of 2 g/kg initially, followed by maintenance therapy of 1 g/kg every 2-4 weeks, but showing minimal response to corticosteroids or plasma exchange 1. Some studies suggest that MMN with and without conduction block may be similar or distinct diseases, but they share similar clinical features and response to IVIg treatment 3. The presence of anti-GM1 antibodies in 30-80% of patients with MMN is a notable laboratory finding, whereas CIDP may show elevated cerebrospinal fluid protein without significant antibody markers 4, 5. Early diagnosis and treatment of MMN are crucial to prevent irreversible axonal damage and permanent disability, making the distinction between these conditions clinically significant for proper management. Some of the key differences between MMN and CIDP are:
- Clinical presentation: MMN presents with asymmetric, purely motor weakness, while CIDP presents with symmetric weakness and sensory symptoms.
- Electrophysiological findings: MMN is characterized by conduction blocks in motor nerves, while CIDP shows demyelination in both motor and sensory nerves.
- Treatment response: MMN responds well to IVIG, while CIDP responds to multiple immunomodulatory treatments including IVIG, corticosteroids, and plasma exchange.
- Laboratory findings: MMN often shows anti-GM1 antibodies, while CIDP may show elevated cerebrospinal fluid protein without significant antibody markers. Overall, MMN with conduction block is a distinct clinical entity that requires early diagnosis and treatment to prevent long-term disability, and its distinction from CIDP is crucial for proper management 1, 3.