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Trismus is difficulty opening the jaw. It occurs when scar tissue forms in the jaw muscles or jaw joint, which is called the temporomandibular joint, or TMJ. Trismus can also develop when the jaw muscles or joint are damaged.


Trismus may be caused by certain diseases such as tetanus or cancer. It can also be caused by cancer treatments such as radiation therapy and surgery for head and neck cancers. The risk of developing trismus is greater if you receive both of these treatments.

Trismus develops slowly after treatment has finished. It usually develops over a period of 12–18 months. Once trismus develops, it is irreversible.


Symptoms of trismus include:

  • stiff jaw
  • inability to open the mouth wide
  • pain when trying to open the mouth

Trismus can affect your quality of life. If you can’t open your jaw properly, your speech may be difficult to understand. You may only be able to put a very small amount of food in your mouth, which can lead to problems with nutrition. People with trismus may only be able to swallow liquids.

Not being able to fully open your mouth may make it difficult to brush and floss your teeth and to maintain good oral hygiene.

Preventing trismus

Because trismus is irreversible, the focus is on prevention.

Your healthcare team will give you exercises such as the following to help you prevent and manage trismus. It is important to do the exercises every day, 20–30 times a day. Your doctor may also prescribe a pain medicine if it is painful to do the exercises. Exercises may be started during radiation therapy. After surgery, the doctor may recommend when to start the exercises. This is usually after the tissues have healed, about 4–6 weeks after surgery.

  • Open the mouth against gentle pressure by pressing one hand underneath the lower jaw. Place a finger of one hand on the top front teeth, a finger from the second hand on the bottom teeth and pull the mouth open as wide as possible.
  • Use tongue blades, or stacked blades, to help you open your mouth as wide as possible. Your healthcare team may also recommend special devices such as TheraBite and corkscrew.
  • Open your mouth as if yawning. Keep it open for 2 minutes. Rest for 1 minute and then repeat.


Dr Darren Brenner The impact of lifestyle and the environment on cancer

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