multifocal motor neuropathy

Epidemiology

• adults

Pathology

• disease of lower motor neurons

Clinical manifestations

• asymmetrical muscle weakness
• fasciculations (often)
• cramping
• weakness without objective sensory loss in the distribution of two or more of the following nerves:
  • median nerve
  • ulnar nerve
  • radial nerve
  • peroneal nerve
  • tibial nerve
• during the early stages of symptomatic weakness, diffuse, symmetric weakness excludes diagnosis
• absence of each of upper motor neuron signs
• diagnosis is a difficult one

Diagnostic procedures

• nerve conduction studies
  • definite conduction block present in 2 or more nerves outside of common entrapment sites
    • median nerve at wrist
    • ulnar nerve at elbow or wrist
    • peroneal nerve at fibular head
  • normal sensory nerve conduction velocity across the same segments with demonstrated motor conduction block.
  • normal results for sensory nerve conduction studies on all tested nerves, with a minimum of 3 nerves tested

More general terms

• motor neuropathy