Tetanus is a rare disease in developed countries. The incidence of tetanus ranges from 10,000 to 1 million cases per year globally, with only 50–100 of those cases occurring in the United States. Success in prevention of tetanus is largely due to vaccination programs. In developed countries, tetanus is most commonly seen in older persons, recent immigrants, and IV drug users who have not maintained adequate tetanus immunization. Tetanus is caused by an exotoxin produced by Clostridium tetani, an anaerobic, spore-forming, gram-positive rod found widely in soil and in the GI tract.
The toxin tetanospasmin is produced in wounds by C. tetani under anaerobic conditions. The toxin travels by retrograde axonal transport through peripheral motor nerves to synapses in the CNS. There, it inhibits the release of the presynaptic inhibitory neurotransmitters gamma-aminobutyric acid (GABA) and glycine. The loss of inhibitory transmission results in intense muscle spasms.
Tetanospasmin is an extremely potent toxin. Fatal tetanus can result from a minor puncture wound in a susceptible individual.
The incubation period between the initial wound and the development of symptoms averages 1–2 weeks (range, 2–56 days). The wound is not apparent in about 5% of cases. Wound cultures are positive for C. tetani only about one-third of the time. There are several different clinical forms of tetanus; generalized, localized, cephalic, and neonatal.
Generalized tetanus is the most common form of tetanus. The most common initial complaint is pain and stiffness of the jaw, progressing to trismus, risus sardonicus ("sardonic grin"), and opisthotonus over several days. Uncontrollable and painful reflex spasms involving all muscle groups are precipitated by minimal stimulation and can result in fractures, rhabdomyolysis, hyperpyrexia, and asphyxia. The patient remains awake during the spasms, which may persist for days or weeks.
A syndrome of sympathetic hyperactivity often accompanies generalized tetanus, with hypertension, tachycardia, arrhythmias, and diaphoresis that may alternate with hypotension and bradycardia.
Localized tetanus occurs when circulating anti-toxin prevents systemic spread of the toxin. This causes similar painful muscle contractions, but only in the region of the wound.
Cephalic tetanus has been associated with head wounds and involves only the cranial nerves. CN VII is the most commonly affected, though any cranial nerve with motor function can be affected.
Neonatal tetanus can occur as a result of inadequate maternal immunity or poor hygiene, especially around the necrotic umbilical stump.
Is based on the finding of characteristic muscle spasms in an awake person with a wound and an inadequate immunization history. Strychnine poisoning produces identical muscle spasms and should be considered in the differential diagnosis. Other considerations include hypocalcemia, neuroleptic malignant syndrome, seizures, stiff-man syndrome, and dystonic reactions.
Specific levels. There are no specific toxin assays. A ...