Tetanus

Introduction

• 1 million cases per year worldwide; 20-30% mortality
• Elderly patients often have waning immunity and lack of boosters
• Diabetics and IVDU are at increased risk
• Puncture wounds account for 50% of cases in developed countries

Pathophysiology

• Acute, often fatal disease due to C. tetani anaerobic gram-positive rod
• Spores are ubiquitous in soil and animal faeces
• Usually introduced to wounds or injection sites as spore-forming non-invasive state but can germinate into toxin-producing vegetative form if oxygen tension drops i.e. crushed tissue, devitalised tissue, foreign body or infected wound
• Two exotoxins: tetanolysin (promotes replication) and tetanospasmin (all clinical sequelae)
• Tetanospasmin reaches nervous system via bloodstream to peripheral nerves and then retrograde neuronal transport
• Bloodborne tetanospasmin doesn’t cross BBB but retrograde neuronal transport allows it to reach CNS
• Tetanospasmin acts at motor end plates of skeletal muscle, spinal cord, brain and SNS
• Prevents release of inhibitory neurotransmitters glycine and GABA from presynaptic terminals leading to sympathetic overactivity, tetany and spasm
• No person-to-person transmission is possible

Clinical features

• Generalised muscular rigidity, violent muscular contractions and autonomic instability
• No wound is found in 10% of cases
• Can also develop from surgical procedures, otitis media, IVDU or umbilical stump infection in neonates
• Incubation period 24 hours to 1 month
• The shorter the incubation, the more severe the disease
• Generalised, cephalic and local variants

Clinical features

• Generalised tetanus
  • 80% of cases
  • Pain and stiffness in masster (lockjaw)
  • The shorter the axons, the earlier the muscle is affected (hence face)
  • Trismus leads to risus sardonicus
  • Dysphagia, opisthotonos flexing of arms, clenching of fists, extension of lower extremities
  • Mental status is normal
  • Laryngospasm and respiratory muscle spasm can be life threatening
    Hypersympathetic state occurs during second week and can be life-threatening
  • Spasms can last 3-4 weeks and recovery can take months with axonal regrowth
  • Complications include rhabdo and long-bone fracture, PE, pneumonia and sepsis (prolonged hospitalisation)

Clinical features

• Neonatal tetanus
  • Form of generalised tetanus in infants born to inadequately immunised mothers after unsterile treatment of umbilical stump
  • Weak, irritable, weak suck and deterioration in 2nd week of life
• Cephalic tetanus
  • Follows injuries to head or otitis media with CN dysfunction (mostly CN VII)
  • Poor prognosis
• Local tetanus
  • Focal spasticity/hypertonia near wound
  • Resolves over weeks to months
  • Can progress to generalised form

Diagnosis

• Clinical diagnosis
• No lab diagnosis
• C. tetani can be cultured from wounds without tetanus disease
• DDx
  • Strychnine poisoning
  • Dystonic reaction
  • Hypocalcaemia tetany
  • Neuroleptic malignant syndrome
  • Serotonin syndrome
  • Stiff man syndrome
  • Peritonsillar abscess
  • Peritonitis
  • Meningeal irritation
  • Rabies
  • TMJ disease

Treatment

• Admit to ICU
• Respiratory compromise requires paralysis and RSI
• Minimise environmental stimuli to limit reflex convulsive spasms
• Tetanus IG
  • Neutralises circulating tetanospasmin and toxin in wound but NOT toxin fixed in nervous system already
  • Thus reduces mortality without improving symptoms
  • 3000-6000IU IM once only (half-life 28 days)
• Wound management (debridement)
• Metronidazole 500mg IV BD
• IV midazolam for muscle relaxation (often large doses)

Treatment

• Autonomic dysfunction
  • Magnesium sulphate
  • Labetalol
  • Morphine
  • Clonidine
• Active immunisation
  • Disease does not confer immunity
  • ADT if over 10yo or DTPa if under 7

Prevention

• Only 60% of patients receive appropriate tetanus wound prophylaxis
• Everyone needs primary series of 3 vaccinations plus 2 boosters; after that do NOT need 10 yearly boosters

Tetanus-prone wounds

• Compound fractures
• Deep penetrating wounds
• Wounds containing foreign bodies
• Wounds with pyogenic infection
• Wounds with extensive tissue damage
• Contaminated wounds
• Reimplantation of avulsed tooth

Prevention

Last Updated on October 2, 2020 by Andrew Crofton