Pathophysiology and Management of Tetanus

A Neuromuscular Condition Secondary to a Bacterial Toxin

Feb 23, 2009 Anthony Lee

Tetanus is one of the conditions that a person can be vaccinated for. What exactly is it?

When one hears about tetanus, he or she might recognize it as a condition for which a vaccine is available. Tetanus is like other diseases that vaccines protect against, such as measles, polio, and chickenpox, in that the cause is an infectious microorganism and the consequences without treatment are often serious. Almost all cases of tetanus occur in people who are not fully immunized against it.

Cause and Pathophysiology

Tetanus is caused by the mobile anaerobic gram-positive bacterium Clostridium tetani. It is ubiquitously found over human skin and within dust, manure, soil, clothing, and some human gastrointestinal tracts. The bacterium forms spores that germinate under environments without oxygen, such as wounds. It then forms and releases a pathological toxin called tetanospasmin.

In the human nervous system, there are motor neurons that run from the spinal cord to skeletal muscles in order to stimulate muscle contraction. There are also neurons in the spinal cord called inhibitory neurons that modulate nerve conduction to the muscle. Tetanospasmin makes its way to the spinal cord in the central nervous system, either along peripheral nerves or through the bloodstream. From there, it blocks release of neurotransmitter from the inhibitory neurons, causing excessive nerve conduction to muscle.

Symptoms and Signs

Tetanus is characterized by hypertonic muscle contraction. It may be localized at the site of innoculation of Clostridium tetani or may be more diffuse as the toxin acts in the spinal cord. This can result in stiffness of muscles in the jaw (lockjaw), neck, back, abdomen, arms, and/or legs. In severe cases of tetanus, the patient is unable to breathe because of rigidity of muscles in the diaphragm and chest wall that are responsible for voluntary respiration. The late stage of tetanus may also involve fluctuations in heart rate and blood pressure.

Treatment and Prevention

After diagnosis of tetanus based on the clinical presentation, treatment is delivered promptly. Any present wounds are cleaned and/or cut out (debrided) to remove the source of infection, and human tetanus immune globulin is administered to neutralize any tetanus toxin that has not reached the central nervous system. Antibiotics, such as metronidazole (Flagyl), penicillin G, and doxycycline, may be given but not as sole therapy. Other measures are supportive and address the consequences of tetanus, such as mechanical ventilation for respiratory failure.

Vaccination against tetanus is effective as a preventive measure. It comes in the form of tetanus toxoid that is often injected as part of a vaccine combining diphtheria, tetanus toxoid, and acellular pertussis (DTaP vaccine). Tetanus vaccination is given as a series during childhood and booster shots administered every 10 years. Patients with wounds may be given tetanus vaccination if his or her vaccination history is unknown or reports incomplete immunization against tetanus.

References

The copyright of the article Pathophysiology and Management of Tetanus in General Medicine is owned by Anthony Lee. Permission to republish Pathophysiology and Management of Tetanus in print or online must be granted by the author in writing.

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