Toxin-mediated neuromuscular disease caused by Clostridium tetani — prevention is vaccination; treatment is wound care, antitoxin, and supportive ICU care.
Also known as: tetanus, lockjaw, Clostridium tetani
Overview
Acute, often fatal disease caused by the neurotoxin tetanospasmin produced by Clostridium tetani, a gram-positive spore-forming obligate anaerobe. Characterized by rigidity and reflex spasms of skeletal muscle and autonomic instability.
Epidemiology
Rare in the US (<50 cases/year) due to widespread vaccination. Worldwide ~25,000-50,000 deaths annually, predominantly neonatal tetanus in low-income countries. US cases concentrate in unvaccinated or under-vaccinated adults and IV drug users.
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IV drug use (subcutaneous heroin injection — 'skin popping')
Puncture wounds, burns, deep contaminated wounds with devitalized tissue
Neonatal tetanus (umbilical stump contamination in non-sterile delivery)
Diabetes mellitus
Pathophysiology
Tetanospasmin is taken up by motor neurons and transported retrograde to the spinal cord, where it blocks release of inhibitory neurotransmitters (glycine and GABA) from Renshaw cells. The resulting loss of inhibition causes uncontrolled motor neuron firing → sustained muscle rigidity and reflex spasms. Sympathetic autonomic dysregulation produces hypertension, tachycardia, arrhythmias.
Clinical presentation
Symptoms
Incubation 3-21 days (shorter incubation = worse prognosis)
Trismus ('lockjaw') — earliest sign, masseter rigidity (~75% of cases)
Risus sardonicus (sustained facial grin from facial muscle spasm)
Neonatal tetanus: poor sucking, generalized rigidity, opisthotonus in days 4-14 of life
Classic findings
Trismus, risus sardonicus, opisthotonus, and reflex spasms in a patient with an unattended wound and incomplete vaccination history — clinical diagnosis.
Differential diagnosis
Strychnine poisoning — Glycine receptor antagonism produces near-identical presentation; toxicology screen and history
Dystonic reaction (neuroleptic, metoclopramide) — Recent dopamine antagonist; resolves with diphenhydramine or benztropine
Clinical: trismus, generalized muscle rigidity, reflex spasms, autonomic dysfunction in a patient with consistent exposure (wound, IV drug use) and inadequate vaccination.
Labs
Clinical diagnosis — no specific lab confirms tetanus
Wound culture insensitive (positive in only ~30%) and not diagnostic
Routine CBC, CMP, CK (elevated from muscle activity)
Anti-tetanus antibodies — adequate level virtually excludes diagnosis but not always feasible acutely
Imaging
Imaging used to evaluate alternative diagnoses
CT/MRI brain to rule out central causes of trismus
Diagnostic algorithm
Wound Type
<3 doses or unknown
≥3 doses — booster due
≥3 doses — booster not due
Clean, minor
Td/Tdap; no TIG
Td/Tdap if last dose >10 yr
No vaccine, no TIG (last dose ≤10 yr)
Dirty, major, puncture, burn
Td/Tdap PLUS TIG 250 IU IM
Td/Tdap if last dose >5 yr
No vaccine, no TIG (last dose ≤5 yr)
Tetanus post-exposure prophylaxis based on wound type and vaccination history (CDC).
Treatment
First-line
ICU admission with quiet, dimly lit environment to minimize stimuli
Wound debridement to eliminate spore reservoir
Human tetanus immune globulin (HTIG) 500 units IM (some use 3,000-6,000 IU) — neutralizes circulating toxin; toxin already bound is not neutralized
Tetanus toxoid (Td or Tdap) at a different site — clinical disease does not produce protective immunity
Antibiotics: metronidazole 500 mg IV q6-8h (preferred) × 7-10 days; alternative penicillin G but GABA antagonism may worsen spasms
Benzodiazepines (diazepam, midazolam, lorazepam) for muscle spasms and sedation
Magnesium sulfate infusion for autonomic instability
Intubation and neuromuscular blockade (vecuronium) for severe spasms or respiratory failure
Baclofen (intrathecal in refractory cases)
Beta-blockers (labetalol) or alpha-blockers for autonomic storm
Second-line / adjunct
Dantrolene for refractory muscle rigidity
Tracheostomy for prolonged ventilation
Nutritional support, DVT prophylaxis
Complications
Respiratory failure from laryngospasm or sustained chest wall rigidity
Aspiration pneumonia
Autonomic storm with arrhythmias, cardiac arrest
Vertebral compression fractures and long-bone fractures from violent spasms
Rhabdomyolysis, AKI
Death (10-20% even with optimal care; >40% in elderly and neonates)
PANCE pearls
Wound management for tetanus prophylaxis: clean minor wound + ≥3 prior doses → Td if last dose >10 years ago. Dirty/major wound + ≥3 doses → Td if >5 years. Any wound + <3 doses or unknown → Td plus TIG (250 units IM) for dirty/major wounds.
Use Tdap rather than Td if the patient has not received Tdap previously (single Tdap, then Td boosters).
Tetanus disease does NOT produce immunity — always give toxoid even after recovery.
Metronidazole is preferred over penicillin (penicillin is itself a GABA antagonist and may worsen spasms).
Magnesium reduces both autonomic instability and spasm intensity; target serum Mg 2.5-4 mmol/L.
References
CDC — Pinkbook: Tetanus — Epidemiology and Prevention of Vaccine-Preventable Diseases (chapter)
ACIP — Updated Recommendations for Use of Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine (MMWR)
WHO — Current recommendations for treatment of tetanus during humanitarian emergencies
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