General
- CNS disorder leading to muscle spasms caused by Clostridium tetani (soil) toxin
- Controlled in most countries due to childhood tetanus toxoid vaccination
Incidence
- Rare in developed countries
- Slightly more common in developing countries
Risk Factors
- Unimmunised with dirty infected wounds with unhealthy tissue and FB
- Inadequate vaccination
- Penetrating injury with c.tetani inoculation
- Bacterial coinfection
- Devitalised tissue
- FB
- Localised ischaemia
- Patient groups
- Neonates (infected umbilical stump)
- Obstetric (septic abortion)
- Post-surgical pts (necrotising infections)
- Dental infections
- IVDU
- Infected DM foot ulcers
Microbiology
- Clostridium tetani = obligate anaerobe
- Spores found in mammalian GIT and soil
- Enters damaged human tissue (dirty wounds) = inoculation
- Transforms into a vegetative bacilli
- Produces Exotoxin
- metalloproteinase tetanus toxoid (tetanospasmin)
- Enters CNS (retrograde axonal transport)
- Blocks inhibitory interneuron transmission = DISINHIBITION of anterior horn and AN system
- Increased muscle tone
- Painful spasms
- Widespread autonomic instability
- Hypersympathetic state - sweating, tachy, HTN (via loss of adrenal medulla control SNS)
- Effects = long lasting because recovery involves new axon nerve terminal growth
Clinical
- Incubation = 3-21 days
- Presents in 4 ways
- Generalized
- Local (rare)
- Cephalic e.g. CN only and can mimic stroke
- Neonatal - poor aseptic technique and mum unimmunised
- Symptoms
- Apnea, AW obstruction - thoracic, glottic, pharyngeal
- Trismus
- Painful tonic contraction of skeletal muscle
- Autonomic overactivity - sweating, tachycardia, HTN
- Stiff neck, sardonic smile, rigid abdo
- Fists clenched, back arched, flex and abduct arms, extend legs and apneic during episode
- Duration of sx usually 4-6 weeks
Investigations
- Clinical dx
- R/O mimic pathologies
Differential diagnosis
- Drug induced dystonias
- Dental infection - trismus
- Rat poison ingestion
- Malignant neuroleptic syndrome
Management
- Goals
- Supportive care
- Stop toxin production
- Neutralize unbound toxin
- Protect airway
- Control muscle spasms
- Management of autonomic nervous system dysfunction
- What to do
- Admit to ICU for intubation, early trache, sedation and NM blockade
- Wound debridement
- Abx - IV Metronidazole
- Give tetanus antitoxin - 500 units IM one off (human tetanus immune globulin)
- Dual BB (labetalol, Morphine, Mg sulfate for ANS sx)
- Immunise - 3 doses of DTaP
- Supportive care
- ICU admission
- Aggressive and early airway management
- Muscle relaxant
- Relaxation
- Sedatives - benzos (10mg diazepam)
- NM blockade - vecuronium
- Autonomic dysfunction
- For hypertension and tachycardia
- Mg sulf, Labetalol, Morphine, clonidine
- Stop toxin production
- Wound debridement
- Abx
- Metronidazole 500mg IV TDS 10/7
- Neutralize Unbound Toxin
- Neutralization of Toxin
- HTIG = human tetanus immune globulin = tetanus antitoxin
- 500 units IM single dose (around wound and elsewhere)
- (Tetanus toxin irreversibly binds tissues, so target unbound toxin)
- Immunisation
Immunisation
- 3 doses
- Normally part of vaccine schedule in NZ
- DTaP
- Don’t get immune when get infection so still need full imms
Prognosis
- Neonatal - usuall fatal
- Undeveloped - high mortality rate up to 50%
- Developed - usually survive with modern technology and access to care