ESSENTIALS OF DIAGNOSIS
History of wound and possible contamination.
Jaw muscle stiffness (“lock jaw”), then spasms (trismus).
Stiffness of the neck and other muscles, dysphagia, irritability, hyperreflexia.
Finally, painful convulsions precipitated by minimal stimuli.
Tetanus is caused by the neurotoxin tetanospasmin, elaborated by C tetani. Spores of this organism are ubiquitous in soil and may germinate when introduced into a wound. The vegetative bacteria produce tetanospasmin, a zinc metalloprotease that cleaves synaptobrevin, a protein essential for neurotransmitter release. Tetanospasmin interferes with neurotransmission at spinal synapses of inhibitory neurons. As a result, minor stimuli result in uncontrolled spasms, and reflexes are exaggerated. The incubation period is 5 days to 15 weeks, with the average being 8–12 days.
Most cases occur in unvaccinated individuals. Persons at risk are older adults, migrant workers, newborns, and injection drug users. While puncture wounds are particularly prone to causing tetanus, any wound, including bites or decubiti, may become colonized and infected by C tetani.
The first symptom may be pain and tingling at the site of inoculation, followed by spasticity of the muscles nearby. Stiffness of the jaw, neck stiffness, dysphagia, and irritability are other early signs. Hyperreflexia develops later, with spasms of the jaw muscles (trismus) or facial muscles and rigidity and spasm of the muscles of the abdomen, neck, and back. Painful tonic convulsions precipitated by minor stimuli are common. Spasms of the glottis and respiratory muscles may cause acute asphyxia. The patient is awake and alert throughout the illness. The sensory examination is normal. The temperature is normal or only slightly elevated.
The diagnosis of tetanus is made clinically.
Tetanus must be differentiated from various acute central nervous system (CNS) infections such as meningitis. Trismus may occasionally develop with the use of phenothiazines. Strychnine poisoning should also be considered.
Airway obstruction is common. Urinary retention and constipation may result from spasm of the sphincters. Respiratory arrest and cardiac failure are late, life-threatening events.
Tetanus is preventable by active immunization (see Table 30–7). For primary immunization of adults, Td (tetanus and diphtheria toxoids vaccine) is administered as two doses 4–6 weeks apart, with a third dose 6–12 months later. For one of the three doses, Tdap (tetanus toxoid, reduced-dose diphtheria toxoid, acellular pertussis vaccine) should be substituted for Td. Booster Td doses are given every 10 years or at the time of major injury if it occurs more than 5 years after a dose; a single dose of Tdap is preferred to Td for wound management if the patient has not been previously vaccinated with Tdap. Women should receive Tdap with each pregnancy, preferably between 27 and 36 weeks, with immunization at 27–30 weeks associated with the highest antibody concentrations.
Passive immunization should be used in nonimmunized individuals and those whose immunization status is uncertain whenever a wound is contaminated or likely to have devitalized tissue; tetanus immune globulin, 250 units, is given intramuscularly. Active immunization with tetanus toxoid vaccine is started concurrently. Table 33–2 provides a guide to prophylactic management.
Table 33–2.Guide to tetanus prophylaxis in wound management. ||Download (.pdf) Table 33–2. Guide to tetanus prophylaxis in wound management.
|History of Absorbed Tetanus Toxoid ||Clean, Minor Wounds ||All Other Wounds1 |
|Tdap or Td2 ||TIG3 ||Tdap or Td2 ||TIG3 |
|Unknown or < 3 doses ||Yes ||No ||Yes ||Yes |
|3 or more doses ||No4 ||No ||No5 ||No |
Human tetanus immune globulin, 500 units, should be administered intramuscularly within the first 24 hours of presentation. Whether intrathecal administration has any additional benefit is controversial. An unblinded, randomized trial comparing intramuscular tetanus immune globulin to intramuscular plus intrathecal tetanus immune globulin found clinical benefit in the intrathecal group. However, the exact immunoglobulin preparation was not specified and the total dose was 4000 units. Tetanus does not produce natural immunity, and a full course of immunization with tetanus toxoid should be administered once the patient has recovered.
Debridement of wounds should be undertaken if implicated as the source. Metronidazole, 7.5 mg/kg administered intravenously or orally every 6 hours (maximum 4 g daily), is preferred and should be administered to all patients. Penicillin, 20 million units intravenously daily in divided doses, is an alternative. Minimal stimuli can provoke spasms, so the patient should be placed at bed rest and monitored under the quietest conditions possible. Sedation, paralysis with curare-like agents, and mechanical ventilation are often necessary. Enteral nutritional support should be given early.
High mortality rates are associated with a short incubation period, early onset of convulsions, and delay in treatment. Contaminated lesions about the head and face are more dangerous than wounds on other parts of the body.
et al. Association between third-trimester Tdap immunization and neonatal pertussis antibody concentration. JAMA. 2018 Oct 9;320(14):1464–70.