eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease
Tetanus
Updated: Jan 23, 2009
Introduction
Background
Tetanus is an intoxication characterized by increased muscle tone and spasms caused by the release of the neurotoxin tetanospasmin by Clostridium tetani following inoculation into a human host. Tetanus occurs in several clinical forms, including generalized, cephalic, localized, and neonatal disease.
Pathophysiology
Most cases of tetanus are caused by direct contamination of wounds with clostridial spores. Wounds with low oxidation-reduction potential, such as those with dead or devitalized tissue, a foreign body, or active infection, are ideal for germination of the spores and release of toxin. Infection by C tetani results in a benign appearance at the portal of entry because of its inability to evoke an inflammatory reaction (unless co-infection with other organisms develops).
Tetanospasmin, a zinc metalloprotease, is released in the wound and binds to the peripheral motor neuron terminal, enters the axon, and, via retrograde intraneuronal transport, reaches the nerve cell body in the brainstem and spinal cord. The toxin migrates across the synapse to presynaptic terminals where it blocks the release of the inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA) by cleaving proteins crucial for the proper functioning of the synaptic vesicle release apparatus. One of these important proteins is synaptobrevin. This diminished inhibition results in an increase in the resting firing rate of the motor neuron, which is responsible for the observed muscle rigidity.
The lessened activity of reflexes limits the polysynaptic spread of impulses (a glycinergic activity). Agonists and antagonists may be recruited rather than inhibited, with consequent production of spasms. Loss of inhibition may also affect preganglionic sympathetic neurons in the lateral gray matter of the spinal cord and produce sympathetic hyperactivity and high levels of circulating catecholamines. Finally, tetanospasmin can block neurotransmitter release at the neuromuscular junction, causing weakness and paralysis.
Localized tetanus develops when only the nerves supplying the affected muscle are involved. Generalized tetanus develops when the toxin released at the wound spreads through the lymphatics and blood to multiple nerve terminals. The blood-brain barrier prevents direct entry of toxin to the CNS.
Frequency
United States
Neonatal tetanus is rare. Tetanus affects nonimmunized persons, partially immunized persons, or fully immunized individuals who do not maintain adequate immunity with periodic booster doses. The risk for development of tetanus and for the most severe form of the disease is highest in the elderly population. Most cases follow an acute injury, such as a puncture wound, a laceration, or an abrasion.
Tetanus can be acquired outdoors as well as indoors. The injury is usually trivial, and, often, no initial medical treatment is sought. Tetanus can also develop as a complication of some chronic conditions, such as decubitus ulcers, abscesses, and gangrene. Finally, it may complicate burns, frostbite, middle ear infections, surgery, abortion, childbirth, and intravenous or subcutaneous drug use. Fewer than 50 cases of tetanus per year have been recorded since 1995. The infection has not been transmitted from person to person.
International
C tetani is found worldwide in soil, on inanimate objects, in animal feces, and, occasionally, in human feces. The disease is common in areas where soil is cultivated, in rural areas, in warm climates, during summer months, and among males. In countries without a comprehensive immunization program, tetanus predominantly develops in neonates and young children.1
Mortality/Morbidity
A rating scale for the severity and the prognosis of tetanus is described below.2
- Score one point for each of the following:
- Incubation period less than 7 days
- Period of onset less than 48 hours
- Acquired from burns, surgical wounds, compound fractures, septic abortion, umbilical stump, or intramuscular injection
- Narcotic addiction
- Generalized tetanus
- Temperature greater than 104°F (40°C)
- Tachycardia greater than 120 beats per minute (>150 beats per minute in neonates)
- Total score indicates the severity and the prognosis as follows:
- Score of 0-1 indicates mild severity with less than a 10% mortality rate.
- Score of 2-3 indicates moderate severity with a 10-20% mortality rate.
- Score of 4 indicates severe tetanus with a 20-40% mortality rate.
- Score of 5-6 indicates very severe tetanus with greater than a 50% mortality rate.
- Cephalic tetanus is always severe or very severe.
- Neonatal tetanus is always very severe.
Race
No particular racial predilection has been reported.
Sex
No sex predilection has been reported, except to the extent that males may have more soil exposure in some cultures.
Age
Neonatal tetanus is most common in countries without comprehensive vaccination programs. Otherwise, most severe disease develops in elderly people. Age predilection is mostly governed by soil exposure patterns.
Clinical
History
The etiologic agent of tetanus, C tetani, is an anaerobic, motile, gram-positive rod that forms an oval, colorless, terminal spore and assumes a shape that resembles a tennis racket or a drumstick. The organism is found worldwide. The spores may survive for years in some environments and are resistant to disinfectants and to boiling for 20 minutes. Vegetative cells are easily inactivated and are susceptible to several antibiotics. Patients sometimes remember an injury, but, many times, the injury goes unnoticed.
- Generalized tetanus: Generalized tetanus is the most commonly found form of tetanus in the United States, accounting for 85-90% of cases. The extent of the trauma varies from trivial injury to contaminated crush injury. The incubation period is 7-21 days, largely depending on the distance of the injury site from the CNS. Trismus is the presenting symptom in 75% of cases; a dentist or an oral surgeon often initially sees the patient. Other early features include irritability, restlessness, diaphoresis, and dysphagia with hydrophobia, drooling, and spasm of the back muscles. These early manifestations reflect involvement of bulbar and paraspinal muscles, possibly because they are innervated by the shortest axons. The condition may progress for 2 weeks despite antitoxin therapy because of the time needed for intra-axonal antitoxin transport.
- Localized tetanus: Localized tetanus involves an extremity with a contaminated wound and widely varies in severity. This is an unusual form of tetanus and the prognosis for survival is excellent.
- Cephalic tetanus: Cephalic tetanus generally follows head injury or develops with infection of the middle ear. Symptoms consist of isolated or combined dysfunction of the cranial motor nerves (most frequently the seventh cranial nerve). It may remain localized or progress to generalized tetanus. This is an unusual form of tetanus with an incubation period of 1-2 days. The prognosis for survival is usually poor.
- Tetanus neonatorum: This is generalized tetanus that results from infection of a neonate. It primarily occurs in underdeveloped countries and accounts for up to one half of all neonatal deaths. The usual cause is the use of contaminated materials to sever or dress the umbilical cord in newborns of unimmunized mothers. The usual incubation period after birth is 3-10 days, which is why it is sometimes referred to as the disease of the seventh day. The newborn usually exhibits irritability, poor feeding, rigidity, facial grimacing, and severe spasms with touch. The mortality rate exceeds 70%.
Physical
- Generalized tetanus: Sustained trismus may result in the characteristic sardonic smile (risus sardonicus) and persistent spasm of the back musculature may cause opisthotonus. Waves of opisthotonus are highly characteristic of the disease. With progression, the extremities become involved in episodes of painful flexion and adduction of the arms, clenched fists, and extension of the legs. Noise or tactile stimuli may precipitate spasms and generalized convulsions. Involvement of the autonomic nervous system may result in severe arrhythmias, oscillation of the blood pressure, profound diaphoresis, hyperthermia, rhabdomyolysis, laryngeal spasm, and urinary retention. In most cases, the patient remains lucid.
- Localized tetanus: In mild cases, patients may have weakness of the involved extremity, presumably due to partial immunity. In more severe cases, intense painful spasms occur and usually progress to generalized tetanus.
- Cephalic tetanus: Cranial nerve findings and rapid progression are typical. This form may remain localized or progress to generalized tetanus.
- Tetanus neonatorum: Physical examination findings are similar to generalized tetanus findings.
Causes
- Causes of tetanus include underimmunization and the use of contaminated materials in newborn care.
More on Tetanus |
 Overview: Tetanus |
| Differential Diagnoses & Workup: Tetanus |
| Treatment & Medication: Tetanus |
| Follow-up: Tetanus |
| References |
| Further Reading |
| Next Page » |
References
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Further Reading
An interesting online case is available at the Gorgas Course in Clinical Tropical Medicine.
Keywords
tetanus, abscesses, airway obstruction, burns, cephalic tetanus, Clostridium tetani, C tetani, compound fractures, contaminated crush injury, decubitus ulcers, disease of the seventh day, frostbite, gangrene, generalized tetanus, hyperreflexia, hyperthermia, laryngeal spasm, localized tetanus, lockjaw, middle ear infections, neonatal tetanus, opisthotonus, rhabdomyolysis, septic abortion, synaptobrevin, tetanospasmin, tetanus neonatorum, trismus, urinary retention
