Tetanus is caused by an infection with the bacterium Clostridium tetani. The bacterial spores are present in soil, dust and animal manure; they remain infectious in the environment for an extended period. Tetanus infection typically occurs through a dirty skin wound. Once in the body, the bacteria produce a nervous system toxin called tetanospasmin. The toxin blocks the release of neurotransmitters, leading to painful muscle spasms and contractions. Routine childhood immunizations include protection against tetanus, which has made the disease rare in the U.S. The Centers for Disease Control and Prevention reported 41 cases of tetanus nationally in 2006.
Facial Spasms and Trismus
The effects of the tetanus toxin usually begin with facial muscle spasms. Spasms of the muscles above the forehead and around the mouth can produce a characteristic facial expression known as risus sardonicus, which is characterized by raised eyebrows and an unnatural fixed smile. The jaw muscles typically become stiff, making it difficult to open the mouth. In the extreme, the mouth is stuck in a closed position--a condition known as trismus or more commonly, lockjaw.
Generalized Muscle Spasms
Painful muscles spasms can occur throughout the body, including the in neck, trunk, arms and legs. Spasms can last for several minutes and often create bizarre body postures that cannot be controlled. Opisthotonus is one such posture in which the neck and back arch backward giving the body the appearance of an archery bow. The muscles of the chest and the internal diaphragm muscle can be affected by spasms, making breathing difficult to impossible. Without medical intervention, such spasms may be fatal.
Localized Muscle Spasms
Localized tetanus is an uncommon form of the disease characterized by muscle spasms and rigidity that are limited to the area of the body where the injury and infection occurred. This form of the disease may progress to the more common generalized form of the illness.
Cranial Nerve Palsy
Cephalic tetanus is a rare variant of localized tetanus. It is characterized by cranial nerve palsies--weakness or paralysis of muscles of the face that are controlled by one or more specific nerves. Any of the cranial nerves can be involved, but the 7th cranial nerve--the facial nerve--is most commonly affected.
Neonatal Rigidity, Spasms and Poor Feeding
Babies born to mothers without tetanus immunity can contract the infection through the umbilical stump. The condition usually presents with failure to nurse and generalized weakness followed by the development of muscular rigidity and spasms. Neonatal tetanus is virtually unheard of in the U.S., but is common in some developing countries.
Fever and Sweating
Fever and sweating often accompany the muscle spasms of tetanus. An elevated heart rate is often observed on physical examination.
References
- "Principles and Practice of Infectious Diseases, Sixth Edition"; Gerald L. Mandell, M.D., John E. Bennett, M.D., Raphael Dolin, M.D., Editors; 2004
- Centers for Disease Control and Prevention, Pink Book: Tetanus
- Centers for Disease Control and Prevention, MMWR: Prevention of pertussis, tetanus, and diphtheria among pregnant and postpartum women and their infants
- Centers for Disease Control and Prevention, Yellow Book: Tetanus
- National Foundation for Infectious Diseases: Facts about tetanus for adults
