Etiology and Epidemiology
The causative agent of the disease is Clostridium tetani. It is a large motile rod, which is an obligate anaerobe capable of forming spores. The bacterium is ubiquitous, meaning it is widely distributed in the environment. The main reservoir of infection is soil, where spores are excreted along with the feces of herbivores.
Infection occurs via contact transmission. The portal of entry for the infection includes any breaches in the skin or mucous membranes: burns, frostbite, wounds. Deep puncture and lacerated wounds carry the greatest epidemiological threat because they provide the oxygen-free environment ideal for the anaerobic organism to thrive. Neonatal tetanus is a separate category that develops when the umbilical stump becomes infected due to a failure to follow asepsis and antisepsis rules.
Pathogenesis: mechanism of toxin action
Once in the wound, the microbe begins actively producing a specific exotoxin. This neurotoxin has a high tropism for nervous tissue. Via the bloodstream, as well as ascending along endoneurial and perineurial lymphatic spaces, it reaches the reticular formation of the brainstem and spinal cord.
The toxin firmly binds to gangliosides located in the myoneural synapses of skeletal muscles and on neuronal membranes. The primary pathogenetic strike consists of complete blockade of inhibitory impulses in motor neurons. As a result, the absence of inhibitory signals causes continuous tonic tension in the skeletal musculature, against which severe clonic convulsions erupt.
Clinical presentation of the generalized form
The shorter the incubation period, the more acutely the disease manifests and the more severe its course (this pattern is especially pronounced in pediatric practice). The convulsive syndrome is generalized in nature. Any external stimulus, no matter how minor, triggers a seizure due to pronounced hyperesthesia and hyperreflexia. A crucial differential criterion is that the patient's consciousness remains fully preserved during seizures.
Symptoms develop in a strictly descending order:
- Trismus. Tonic spasm of the masticatory muscles. This is the very first sign, which prevents the patient from opening the mouth, speaking, and eating.
- Sardonic smile (risus sardonicus). Spasm of the facial musculature that gives the patient's face a specific expression—a grimace resembling both crying and smiling at the same time.
- Opisthotonos. As the process becomes generalized, the muscles of the limbs and trunk are involved. A sharp contraction of the back extensors occurs, causing the patient to arch, resting on the bed only with their heels and occiput.
Complications and diagnostics
The diagnosis is established primarily based on the characteristic clinical picture. Differential diagnosis is carried out with hysterical seizures, hypokalemic tetany, and strychnine poisoning. The prognosis for tetanus is always regarded as serious. Recovery is extremely slow: in a favorable course, clinical improvement occurs only after 2–8 weeks.
Life-threatening complications are divided into two groups:
- Fatal: development of asphyxia due to spasm of the vocal cords, diaphragm, and respiratory muscles, as well as direct paralysis of the respiratory center. Involvement of the cranial nerves in the process is an extremely unfavorable sign.
- Traumatic: the colossal force of muscle overstrain leads to spontaneous muscle ruptures and severe compression fractures of the spine.
Principles of intensive care
The patient is subject to immediate hospitalization in the intensive care unit. Treatment is comprehensive:
- Focal debridement. Mandatory surgical treatment of the wound to remove the source of toxin production.
- Toxin neutralization. Administration of specific drugs: human tetanus immunoglobulin or equine serum (the latter is administered strictly according to Besredka's method). Simultaneously, tetanus toxoid is administered to stimulate active immunity.
- Cessation of convulsions. Tranquilizers (diazepam) and neuroleptics (chlorpromazine) are prescribed. In severe cases, the patient is transferred to mechanical ventilation using curare-like muscle relaxants, which block the cholinergic receptors of synapses and relieve spasms.
- Antibacterial therapy. Metronidazole is used to suppress the vegetative forms of the bacterium in the wound.
Prevention
The basis of protection is the creation of artificial active immunity. Routine vaccination starts from the age of 3 months according to the National Immunization Schedule (combined vaccines DTaP, Td, multi-component preparations like Pentaxim).
In case of injury, emergency prophylaxis is performed. If the person is vaccinated, only adsorbed tetanus toxoid is administered. Unvaccinated individuals require active-passive immunization as soon as possible: the toxoid is combined with preformed antibodies (serum or immunoglobulin). Nonspecific measures include injury prevention, early surgical wound debridement, and adherence to aseptic rules during childbirth.
The chronology of symptoms of the generalized form can be remembered as moving "from top to bottom": Face (trismus of the masticatory muscles, then sardonic smile) ➔ Trunk (arching into opisthotonos) ➔ Limbs.
Class and exam questions
Why is tetanus particularly dangerous in puncture and lacerated wounds?
The infectious agent is an obligate anaerobe. Deep wound channels create ideal conditions without oxygen access, which is necessary for bacterial reproduction and active exotoxin production.
Does the patient lose consciousness during severe convulsive seizures?
No, the most important differential diagnostic sign of tetanus is the fully preserved, clear consciousness of the patient even during the most severe generalized clonic seizures.
Why is metronidazole included in the tetanus treatment regimen?
This antibacterial drug is necessary for the direct destruction of vegetative forms of clostridia directly at the focus (in the wound), which halts the further synthesis and release of neurotoxin into the blood.
What is the essence of emergency prophylaxis in unvaccinated individuals?
An active-passive immunization strategy is used: the administration of preformed antibodies (serum or immunoglobulin) for the immediate neutralization of the toxin in the blood is combined with the administration of toxoid to trigger the production of one's own long-term immunity.
What else to study on this topic
- Features and clinical picture of the localized (focal) form of tetanus
- Differential diagnosis with strychnine poisoning and hypokalemic tetany
- Neonatal tetanus: epidemiological factors and course features
- Rules for administering anti-tetanus equine serum according to Besredka's method
- Emergency injury prophylaxis regimens depending on vaccination history
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