Tetanus

An acute, potentially fatal neuroinfectious disease caused by the exotoxin tetanospasmin, produced by Clostridium tetani.

Aetiology

Causative Agent

  • Clostridium tetani:
    • Gram-positive, obligate anaerobic bacillus
    • Terminal spore gives characteristic “drumstick” appearance
    • Spores are highly resistant to:
      • Heat
      • Disinfectants
      • Environmental degradation
notion image
  • Produces two toxins:
    • Tetanospasmin (neurotoxin; responsible for clinical disease)
    • Tetanolysin (hemolysin; limited clinical relevance)

Modes of Transmission

  • Not transmitted person-to-person
  • Occurs through environmental exposure:
    • Contaminated wounds
    • Puncture injuries (e.g., nails, thorns)
    • Burns and crush injuries
    • Surgical wounds
    • Umbilical stump contamination
  • Anaerobic conditions favor spore germination.

Pathophysiology

  • Wound contamination → spore germination under anaerobic conditions
  • Vegetative bacteria produce tetanospasmin
  • Toxin enters:
    • Motor nerve terminals
    • Neuromuscular junctions
  • Retrograde axonal transport to:
    • Spinal cord
    • Brainstem
  • Tetanospasmin cleaves synaptobrevin II of Renshaw Cell, blocking release of:
    • GABA
    • Glycine
  • Results in:
    • Loss of inhibitory control
    • Sustained muscle contraction
    • Hyperexcitability of motor neurons

Clinical presentation

Early Symptoms

  • Trismus (lockjaw)
  • Facial muscle stiffness
  • Dysphagia
  • Neck and jaw pain

Progressive Features

  • Generalized rigidity of axial and limb muscles
  • Severe, painful muscle spasms triggered by:
    • Light
    • Noise
    • Touch
  • Opisthotonos
  • Risus sardonicus

Autonomic Dysfunction

  • Labile hypertension and hypotension
  • Tachycardia and bradycardia
  • Cardiac arrhythmias
  • Hyperthermia
  • Profuse sweating

Investigations

  • Primarily clinical
  • No reliable laboratory confirmation

Management

Elimination of Source

  • Surgical wound debridement
  • Removal of necrotic tissue and foreign bodies

Neutralization of Toxin

  • Human tetanus immune globulin (HTIG)/Anti Tetanus Serum (ATS)
    • ATS → 50.000 U IM, then 50.000 U IV
    • HTIG → 3000-6000 U IM SD
  • Prophylaxis
    • ATS → 1 amp = 1.500 U
    • HTIG → 1 pre-filled syringe = 250 U
  • Binds circulating unbound toxin
  • Does not reverse bound toxin effects

Antimicrobial Therapy

  • Metronidazole (first-line) 500mg/6-8hr/IV or 1gr/12hr for 7-10 days
  • Alternatives: Penicillin G 2.4 MU/4-6hr/IV for 7-10 days
  • Goal: prevent further toxin production

Control of Muscle Spasms

  • Benzodiazepines (e.g., diazepam, midazolam)
    • Diazepam 0.1-0.3mg/kg IV, slow injection in 3-5 minutes
    • Diazepam 0.5mg/kg IV or PO/6hr
  • Magnesium sulfate for autonomic instability
    • Loading: 5 g IV, then 2-3 gr/hour
  • Neuromuscular blockade in severe cases

Complications

  • Hyperkalaemia
  • Fluid overload (pulmonary oedema)
  • Severe acidosis (pH <7.15)
  • Uraemic pericardial effusion
  • Severe uraemia (Ur >40)