Tetanus

Tetanospasmin Mechanism

• The tetanospasmin exotoxin is a zinc-dependent endopeptidase that cleaves SNARE proteins (specifically synaptobrevin/VAMP) at the presynaptic terminal
• This prevents the release of inhibitory neurotransmitters GABA (γ-aminobutyric acid) and glycine from interneurons in the spinal cord and brainstem
• Loss of inhibitory tone results in unopposed excitatory neurotransmission, causing sustained muscle contraction

Spinal Cord Pathology

• The toxin specifically targets inhibitory Renshaw cells and interneurons that normally provide reciprocal inhibition between agonist and antagonist muscles
• Without inhibitory input, simultaneous contraction of opposing muscle groups occurs, producing characteristic rigidity and spasms
• The toxin acts irreversibly; symptom resolution depends on sprouting of new nerve terminals and formation of new synapses (explains prolonged recovery period of weeks to months)

Brainstem and Autonomic Involvement

• Involvement of brainstem nuclei leads to trismus (jaw clenching), risus sardonicus (facial grimacing), and opisthotonus (severe back arching)
• Autonomic dysfunction results from toxin effects on brainstem centers regulating sympathetic and parasympathetic outflow, causing dysrhythmias, hypertension, hyperthermia, and profuse diaphoresis
• The toxin does NOT affect sensory nerves or consciousness; patients remain fully alert during spasms

Source of Infection

• Puncture wounds and traumatic injuries with soil/dust contamination (classic scenario: stepping on rusty nail)
• Burns and crush injuries with devitalized tissue providing anaerobic environment
• Surgical wounds and intra-abdominal infections
• Injection drug use with contaminated equipment (increasingly recognized in developed nations)
• Umbilical cord infection (neonatal tetanus in unvaccinated mothers; common in developing countries)
• Chronic wounds, decubitus ulcers, and gangrene
• Dental procedures and oral infections

Risk Factors for Development

• Incomplete or absent vaccination (most significant risk factor)
• Age >60 years with waning immunity
• Contamination of wound with soil, feces, or foreign material
• Delay in wound cleaning and debridement
• Foreign bodies retained in wound
• Crush injuries with tissue necrosis
• Intravenous drug use with non-sterile technique

Classic Triad of Tetanus

• Trismus (lockjaw): rigidity of masseter muscles preventing mouth opening; often the first sign
• Risus sardonicus: characteristic facial grimacing from contraction of facial musculature
• Opisthotonus: severe arching of back and neck from contraction of paraspinal muscles; patient may rest only on occiput and heels

Generalized Tetanus (70-80% of cases)

• Progressive muscle rigidity beginning in jaw and facial muscles, spreading to trunk and extremities over 24-72 hours
• Violent, painful spasms provoked by sensory stimuli (noise, light, touch) or occurring spontaneously
• Dysphagia and dysarthria from laryngeal involvement
• Respiratory compromise from intercostal and diaphragmatic rigidity
• Abdominal wall rigidity simulating acute abdomen
• Hyperreflexia and clonus
• Hyperthermia (often from sustained muscle contraction and autonomic dysfunction)
• Profuse diaphoresis and salivation

Localized Tetanus (rare, 5-10% of cases)

• Spasm and rigidity localized to muscles near the wound
• Better prognosis than generalized disease
• May progress to generalized form

Cephalic Tetanus (rare, <3% of cases)

• Follows head/face trauma or otitis media
• Facial paresis combined with risus sardonicus and trismus
• Highest mortality rate (15-30%)

Neonatal Tetanus

• Presents 3-10 days after birth in unvaccinated mothers
• Poor feeding, weak cry, difficulty sucking
• Progressive rigidity and spasms
• Mortality >80% without treatment

Autonomic Manifestations

• Severe hypertension and tachycardia alternating with hypotension and bradycardia
• Cardiac dysrhythmias (life-threatening)
• Sudden cardiovascular collapse
• Hyperthermia refractory to antipyretics

Clinical Diagnosis (Primary Method)

• Diagnosis is entirely clinical; no pathognomonic laboratory test exists
• Based on clinical presentation and history of inadequate vaccination/wound
• C. tetani is rarely isolated from wound cultures; culture-negative disease is the norm
• Diagnosis should NOT be delayed pending culture results

Diagnostic Criteria

• Onset of symptoms 3 days to 3 weeks after injury (or no visible wound)
• Characteristic presentation: trismus progressing to generalized rigidity and spasms
• Preserved sensory and mental status
• Normal CSF and neuroimaging (helps exclude mimics)

Laboratory Studies (to exclude differential diagnoses)

• CSF analysis: normal glucose, protein, and cell count (excludes meningitis)
• Blood cultures: obtained but usually negative
• Wound culture: low sensitivity; may grow C. tetani but absence does not exclude diagnosis
• Electrolytes: may show hypokalemia and hyperkalemia during spasm-induced rhabdomyolysis
• Creatine kinase (CK): markedly elevated from sustained muscle contraction and hyperthermia
• Myoglobin: elevated; monitor for rhabdomyolysis-induced acute kidney injury
• ABG/pH: metabolic acidosis from hyperthermia and rhabdomyolysis

EMG (Electromyography)

• Shows continuous motor unit action potentials at rest (pathognomonic finding for tetanus)
• Demonstrates persistent electrical activity even during apparent relaxation
• Useful for confirming diagnosis if clinical presentation is atypical

Imaging

• CT/MRI brain and spine: normal (helps exclude other causes of rigidity and spasms)
• Chest X-ray: assess for aspiration pneumonia and respiratory status

Diagnostic Criteria (Modified Pässler and Stoehr)

1. 1.Onset of symptoms 3 days to 3 weeks after known injury
2. 2.History of intravenous drug use, surgical procedures, or specific wound type
3. 3.Any one of: trismus, risus sardonicus, or generalized spasticity
4. 4.Spasms provoked by sensory or spontaneous stimuli
5. 5.Normal CSF
6. 6.Preserved consciousness and sensation

Immediate Stabilization

• Airway management: obtain early tracheal intubation and mechanical ventilation before spasms compromise airway; approximately 50% of patients require intubation
• Tetanic spasm management: muscle relaxants and sedation are cornerstone of treatment
• Continuous cardiac monitoring and ICU-level care
• Avoid triggers of spasms (minimize noise, light, unnecessary stimulation)

Pharmacologic Therapy

1. Muscle Relaxants and Sedation (First-line)

• Benzodiazepines (e.g., lorazepam 2-10 mg IV Q2-4H, or diazepam 5-20 mg IV Q2-4H): GABA receptor agonists that increase inhibitory neurotransmission; provide both spasm control and sedation; can be used as continuous infusion
• Neuromuscular blockade agents (e.g., vecuronium, pancuronium): required if sedation/benzodiazepines inadequate to control spasms or if mechanical ventilation needed; produce paralysis allowing ventilatory support
• Typical ICU regimen: combination of benzodiazepines with neuromuscular blocking agents and opioids (morphine or fentanyl)

2. Tetanospasmin Neutralization

• Human tetanus immunoglobulin (HTIG): 3000-5000 IU IM (single dose); binds unbound circulating toxin in bloodstream, preventing central nervous system penetration
• Equine tetanus antitoxin: less preferred due to serum sickness risk; used only if HTIG unavailable
• Critical timing: efficacy diminishes after toxin has entered CNS; should be given as early as possible
• Does NOT reverse toxin effects on already-internalized toxin (explains ongoing symptoms despite antitoxin)

3. Antimicrobial Therapy

• Metronidazole: 500 mg IV Q6-8H for 7-10 days (preferred agent; excellent CNS penetration and anaerobic coverage)
• Penicillin G: 2-4 million units IV Q4-6H (historical first-line; lower CNS penetration than metronidazole)
• Clindamycin: 600 mg IV Q6-8H (alternative)
• Fluoroquinolone (e.g., levofloxacin): alternative if β-lactam allergy
• Antimicrobials eliminate bacteria from wound; they do NOT inactivate toxin already produced

4. Autonomic Management

• β-blocker (e.g., propranolol 10-20 mg PO TID or IV): manage tachycardia and hypertension
• Labetolol: combined α/β blockade for hypertension
• Morphine/fentanyl: provide analgesia and reduce autonomic outbursts
• Dantrolene or baclofen: may provide additional muscle relaxation in refractory cases
• Avoid vasodilators alone (risk of sudden hypotensive episodes)

Supportive Care

• Mechanical ventilation: often required for days to weeks; prolonged courses common
• Parenteral or enteral nutrition: high metabolic demands; caloric requirements may exceed 5000 kcal/day
• Catheterization: urinary catheter for fluid management during paralysis
• DVT prophylaxis: sequential compression devices and pharmacologic prophylaxis (LMWH) during immobility
• Stress ulcer prophylaxis: H2-blocker or PPI
• Temperature management: cooling blanket for hyperthermia; avoid salicylates (risk of rhabdomyolysis complications)
• Physiotherapy: after acute phase resolves, passive range of motion to prevent contractures

Wound Management

• Primary wound debridement: remove devitalized tissue, foreign bodies, and contamination
• Serial wound inspection: source control essential, though bacteremia rare
• Delayed primary closure if significant contamination; do not close contaminated wounds acutely

Post-Recovery Tetanus Vaccination

• Critical point: tetanus disease does NOT confer immunity (tetanospasmin levels insufficient to stimulate immune response)
• Initiate tetanus toxoid vaccination during convalescence before discharge
• Complete primary series and booster as indicated

Respiratory Complications (Most Common Cause of Death)

• Airway obstruction from trismus and risus sardonicus; may occur before spasms begin
• Aspiration pneumonia from impaired swallowing and protective reflexes
• Hypoxic episodes during spontaneous spasms if inadequate sedation/ventilation
• Ventilator-associated pneumonia in patients on prolonged mechanical ventilation (common; impacts mortality)
• Tetanic apnea: severe spasm of respiratory muscles causing complete cessation of breathing

Cardiovascular Complications

• Autonomic dysrhythmias: sudden cardiac dysrhythmias from brainstem dysfunction (atrial fibrillation, bradycardia, asystole)
• Sudden cardiovascular collapse: catastrophic hypotension or hypertensive crisis with myocardial infarction
• Myocarditis: rare but documented
• Cardiac dysrhythmias triggered by intubation or suctioning

Rhabdomyolysis and Renal Complications

• Rhabdomyolysis: massive sustained muscle contraction releases myoglobin
• Acute kidney injury: from myoglobinuria and hyperthermia; requires aggressive fluid resuscitation and monitoring
• Compartment syndrome: rarely develops from sustained muscle contraction
• Hyperkalemia: from rhabdomyolysis; life-threatening dysrhythmia risk

Metabolic Complications

• Severe hyperthermia: unresponsive to antipyretics; from sustained muscle contraction and autonomic dysfunction
• Metabolic acidosis: from hyperthermia, muscle breakdown, and hypoxia
• Fractures: from violent spasms; notably vertebral compression fractures and long bone fractures
• Dental damage: from jaw clenching and trismus

Secondary Infections

• Nosocomial pneumonia (major cause of prolonged ICU stay and mortality)
• Urinary tract infections: from prolonged catheterization
• Line infections: from central lines and prolonged hospitalization

Prolonged ICU Sequelae

• Nosocomial infections (primary driver of mortality in modern era, not tetanus toxin)
• Prolonged mechanical ventilation dependence: may require tracheostomy
• Psychological trauma: from prolonged paralysis with full consciousness
• Contractures and muscle atrophy: from immobility during acute phase

Prognostic Factors

Poor Prognostic Factors

• Short incubation period (<7 days from wound to symptom onset): indicates high toxin load; mortality 15-40%
• Short period of onset (<48 hours from first symptom to generalized spasms): rapid progression
• Age >60 years: mortality increases significantly with age
• Neonatal tetanus: highest mortality without treatment (>80%)
• Cephalic tetanus: mortality 15-30% (highest among tetanus subtypes)
• Delayed presentation for medical care: worse outcomes
• Severe autonomic involvement: indicates CNS involvement and worse prognosis
• Comorbid cardiopulmonary disease
• Secondary infections during hospitalization

Favorable Prognostic Factors

• Long incubation period (>10 days): lower toxin load
• Localized tetanus: mortality <5% (rarely progresses to generalized form)
• Young age with good baseline health
• Early treatment: early antitoxin, wound debridement, and ICU support improve outcomes
• Adequate vaccination history: partial immunity may reduce severity

Mortality and Outcomes

• Overall case fatality rate: 5-15% in developed countries with ICU care; >50% in untreated cases or developing nations
• Mortality increases dramatically in:
• Patients >60 years: up to 25-40% mortality
• Patients requiring mechanical ventilation: 10-15% mortality
• Nosocomial infections: significantly increases mortality
• Untreated cases: >50% mortality
• ICU length of stay: typically 2-6 weeks if uncomplicated; longer with secondary infections
• Recovery: full neurologic recovery expected in survivors; autonomic symptoms resolve within 1-2 weeks of onset, but muscle rigidity may persist for weeks to months
• Relapse: does NOT occur; immunity develops with appropriate vaccination post-recovery

Natural History

• Progression phase: symptoms worsen over first 3-10 days after onset
• Plateau phase: most severe symptoms persist for 1-2 weeks; spasms provoked by minimal stimuli
• Recovery phase: gradual improvement over 2-4 weeks as new neurom

Buzzwords that clinch the diagnosis

• Triad: trismus (lockjaw) → risus sardonicus → opisthotonus in a fully alert patient with normal sensation and normal CSF. Preserved consciousness during agonizing spasms is the detail examiners love.
• Organism: Clostridium tetani, an obligate anaerobe with terminal spores giving a drumstick or tennis racket appearance; wound cultures are usually negative, so never wait on micro to treat.

Mechanism the stem will test

• Retrograde axonal transport: tetanospasmin travels up motor neurons to the spinal cord and cleaves the SNARE protein synaptobrevin/VAMP in inhibitory interneurons (Renshaw cells), blocking GABA and glycine release → spastic paralysis. Botulinum toxin cleaves SNAREs at the peripheral NMJ instead, blocking acetylcholine → flaccid paralysis. Same toxin family, opposite phenotype.

Single best next steps

• Airway first: intubate early — laryngospasm and respiratory muscle rigidity, not the toxin itself, kill these patients.
• Human tetanus immune globulin: neutralizes only unbound circulating toxin, so give it immediately; it cannot reverse toxin already internalized in neurons.
• Metronidazole is the preferred antibiotic; penicillin G is a GABA-A antagonist and is generally avoided as first choice.

Prophylaxis algorithm (CDC/ACIP) — the most testable table in the topic

• Clean, minor wound: tetanus toxoid–containing vaccine (Td or Tdap) only if <3 lifetime doses or ≥10 years since last dose. No TIG, ever.
• Dirty/puncture/crush wound: vaccine if <3 doses or ≥5 years since last dose; add TIG only when the primary series is incomplete or unknown, injected at a separate site with a separate syringe.
• Pregnancy: ACIP and ACOG recommend Tdap in every pregnancy at 27–36 weeks; maternal antibody also prevents neonatal tetanus from umbilical stump contamination.

Distractors to avoid

• Surviving tetanus does not immunize — start the toxoid series before discharge.
• Mimics: strychnine poisoning (glycine receptor antagonist, near-identical picture), acute dystonic reaction from antipsychotics or metoclopramide (responds to diphenhydramine/benztropine), hypocalcemic tetany (*Chvostek*/*Trousseau*), and peritonsillar abscess causing isolated trismus.