Multifocal motor neuropathy (MMN) is a neuromuscular disease that usually presents with asymmetric weakness in a limb. The clinical pattern is that of mononeuropathy multiplex. The condition is treatable.
 

Clinical features:

• Asymmetric weakness, usually upper limbs, spares cranial nerves, reflexes may be preserved, fasciculations may occur
• Note this is a form of mononeuropathy multiplex

Investigations:

• Serum Anti-GM1 IgM positive, titre >1:350
• Nerve conduction studies NCS:
  • Multifocal motor demyelination
  • Conduction block
  • Normal sensory response

Pathology/Nerve biopsy:

• In some cases evidence of demyelination & remylination
• In some cases: inflammatory cells

Treatment options:

• Intravenous immunoglobulin (IVIg)
• In refractory cases Cyclophosphamide intravenously may be considered
• There appears to be no benefit from Mycophenolate mofetil.

Related articles:

• Neuromuscular disease patterns, mononeuropathy,