Tetanus affects skeletal muscle, a type of striated muscle used in voluntary movement. The other type of striated muscle, cardiac or heart muscle, cannot be tetanized because of its intrinsic electrical properties. Mortality rates reported vary from 40% to 78%. In recent years, approximately 11% of reported tetanus cases have been fatal.
The highest mortality rates are in unvaccinated people and people over 60 years of age. In general, the further the injury site is from the central nervous system, the longer the incubation period.
The shorter the incubation period, the more severe the symptoms. In neonatal tetanus, symptoms usually appear from 4 to 14 days after birth, averaging about 7 days. On the basis of clinical findings, four different forms of tetanus have been described.
Local tetanus is an uncommon form of the disease, in which patients have persistent contraction of muscles in the same anatomic area as the injury. The contractions may persist for many weeks before gradually subsiding. Local tetanus is generally milder; only about 1% of cases are fatal, but it may precede the onset of generalized tetanus.
Cephalic tetanus is a rare form of the disease, occasionally occurring with otitis media (ear infections) in which ''C. tetani'' is present in the flora of the middle ear, or following injuries to the head. There is involvement of the cranial nerves, especially in the facial area.
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