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Trismus (sometimes called lockjaw) is a condition that makes it hard to open the mouth fully. It can happen anytime during treatment, soon after treatment, or years later. Trismus can be mild or severe.
Trismus can be caused by:
Tell your medical team right away if your child has:
If your child has radiation to the head and neck, they might see a speech therapist when radiation starts. The therapist can teach exercises to help prevent trismus.
Most people can open their mouth about 3 fingers wide. To test for trismus, have your child hold their 3 middle fingers sideways. Then, have them put all 3 in their mouth with fingernails pointing toward the throat. If all three fingers fit between the top and bottom front teeth, your child has a normal mouth opening. If your child cannot put 3 fingers in their mouth, they might have trismus.
Trismus can affect your child’s comfort and quality of life. It can also cause:
The earlier your child begins treatment for trismus, the more likely it is to help. Treatments for trismus include:
Your child’s health care provider can tell you if your child needs these treatments and how to do them.
To learn more about trismus, talk with your care team.
Reviewed: October 2022