Polyneuropathy

Basics

Description

  • A peripheral nerve disorder in which many nerves throughout the body malfunction simultaneously
  • Typically affects distal nerves most prominently
  • Acute polyneuropathy causes:
    • Infectious:
      • Toxin-producing bacteria
      • Viruses
    • Autoimmune:
      • Guillain–Barré
    • Toxic (heavy metals):
      • Lead
      • Mercury
    • Drugs:
      • Anticonvulsants (phenytoin)
      • Antibiotics (chloramphenicol, nitrofurantoin, sulfonamides)
      • Chemotherapy (vinblastine, vincristine)
      • Sedatives (hexobarbital and barbital)
    • Cancer:
      • Multiple myeloma
  • Chronic polyneuropathy causes:
    • Diabetes (most common)
    • Alcohol abuse
    • Nutritional deficiencies:
      • Thiamine
      • B12
    • HIV
    • Hypothyroidism
    • Liver failure
    • Kidney failure
    • Lung cancer
    • Chronic inflammatory demyelinating polyneuropathy (CIDM)

Epidemiology

Incidence and Prevalence Estimates
  • In the U.S., the prevalence of polyneuropathy is ∼2% in the general population
  • It is 8% in patients >55 yr of age
  • The most common cause in the U.S. is diabetes and it occurs in ∼50% of diabetics on insulin

Etiology

  • Myelin dysfunction:
    • Parainfectious immune response triggered by antigens that cross-react with antigens in the peripheral nervous system:
      • Encapsulated bacteria:
        • Campylobacter sp.
        • Diphtheria
      • Viruses:
        • Enteric
        • Influenza viruses
        • HIV
      • Vaccines:
        • Influenza
    • Guillain–Barré syndrome:
      • Acute onset due to myelin dysfunction
      • Rapidly progressive weakness and may lead to respiratory failure
    • CIDM:
      • Chronic illness of myelin dysfunction
      • Symptoms may recur or progress over months and years
  • Vasa nervosum compromise:
    • Vascular supply to nerves compromised leading to nerve infarction
    • Causes:
      • Chronic atherosclerosis
      • Vasculitis
      • Infections
      • Hypercoagulable states
      • Axonopathy
    • Primary dysfunction of the axon
    • Most often the result of toxic–metabolic disorders:
      • Diabetes
      • Nutritional deficiencies
      • Drugs/chemicals

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