Masticatory muscle spasm is one of the early symptoms of the onset of Clostridium tetani infection. Clostridium tetani (clostridiumtetani) is the pathogenic bacterium that leads to tetanus, which exists in large quantities in the intestinal tract of humans and animals, and is contaminated with soil by feces and causes disease by wound infection. Cause: When tetanus spasm toxin is produced locally, it causes generalized transverse muscle spasm. After local production, the toxin is absorbed through the motor end plate, along the nerve fiber gap to the nerve cells in the anterior horn of the spinal cord and up to the brainstem, or it can be absorbed lymphatically and reach the central nervous system through the bloodstream. The toxin binds to gangliosides in the nerve tissue, closing the inhibitory synaptic terminals of the spinal cord and preventing the release of glycine and gamma;aminobutyric acid, which disrupts the transmission of normal inhibitory impulses between the upper and lower neurons, resulting in hyperreflexia (abnormally high excitability) and transverse muscle spasm. Tetanus is mostly seen in battle wounds. In addition to traumatic infections, unclean umbilical cord during delivery and poorly sterilized surgical instruments can cause morbidity. Neonatal tetanus (commonly known as umbilical wind) is particularly common. Differential diagnosis: Facial muscle twitching: Facial muscle twitching is also called facial muscle spasm, and its common clinical manifestation is primary facial muscle twitching. When the disease starts, it is mostly intermittent twitching of the orbicularis oculi muscle, which gradually and slowly spreads to other facial muscles on one side of the face. The twitching of the corners of the mouth muscle is the most noticeable, and in severe cases, it may even involve the ipsilateral broad neck muscle. The degree of twitching varies, and can be aggravated by fatigue, nervousness, or voluntary movement, but cannot be imitated or controlled by itself. The incubation period of tetanus is variable, ranging from 1~2 days to 2 months, with an average of 7~14 days. The shorter the incubation period, the higher the death rate. Early onset of the disease there are fever, headache, discomfort, muscle pain and other prodromal symptoms, local muscle twitching, difficulty in opening the mouth, chewing muscle spasm, the patient’s teeth closed, a bitter smile face. Then the neck, trunk and limb muscles contract tonicly, the body is corkscrew, facial purple pincers, breathing difficulties, and finally can die due to asphyxia. The death rate is about 50%, especially in newborns and the elderly.