What is Trismus

Trismus or ‘lockjaw’ has been used to describe any restriction to mouth opening, including restrictions caused by trauma, surgery, or radiation. In the past, this word was often used to describe the effects of tetanus.

Trismus can dramatically affect the quality of life in a variety of ways. Communication is more complicated, oral hygiene is compromised, chewing, and swallowing is more difficult, and there is an increased risk of aspiration.

This limitation in the ability to open the mouth can have serious health implications, including reduced nutrition due to impaired chewing, difficulty in speaking.

It is prevalent among people who are undergoing treatment for cancer of the head and neck. Let’s delve in together in this article to learn more about Trismus.

What is Trismus?

Trismus or ‘lockjaw’ is a painful condition in which the chewing muscles of the jaw become contracted and sometimes inflamed, preventing the mouth from fully opening.

While Trismus is not widespread in the population, it’s sometimes commonly seen in certain groups, particularly in those who –

  • Have had oral surgery to remove their wisdom teeth.
  • Have had head and neck cancer in a region involving structures that influence mouth movements.
  • Have undergone surgery or radiation treatment to the head and neck. (1)

Causes of Trismus

Trismus can occur when there is damage or injury to the muscles of the jaw. Traditionally, causes of Trismus are divided into intraarticular (factors within the temporomandibular joint) and extra-articular (factors outside the joint).

Intra-articular

  • Internal derangement of TMJ/ meniscus displacement
  • Fractured mandibular condyle or intracapsular fracture (2)
  • Traumatic synovitis
  • TMJ dislocation
  • Osteoarthritis
  • Inflammation arthritis (e.g., rheumatoid or psoriatic)
  • Ankylosis
  • Osteophyte formation

Extra-articular

  • Trauma not involving the mandibular condyle
  • Post-surgical Edema
  • Recent prolonged dental treatment (3)
  • Following administration of inferior alveolar nerve block with local anesthesia
  • Hematoma of medial pterygoid
  • Acute infections of the oral tissues especially involving muscles of mastication
  • Tetanus
  • Tetany
  • Local malignancy
  • Myofascial pain/ TMJ dysfunction
  • Radiation fibrosis
  • Fibrosis from burns
  • Submucous fibrosis
  • Systemic sclerosis
  • Myositis ossificans
  • Coronoid hyperplasia
  • Malignant hyperpyrexia
  • Epidermolysis bullosa
  • Drug-associated dyskinesia
  • Psychotic disturbances

Signs and symptoms of Trismus

The most apparent effect of Trismus is difficulty in opening the mouth. Other symptoms may include:

  • Pain in the jaw, even without movement
  • Difficulty or discomfort performing activities that involve opening the mouth wide
  • Inability to chew or swallow certain foods
  • Cramping in the jaw

In the case of Trismus caused by radiation treatment, patients also frequently present with xerostomia, mucositis, and pain as a result of radiation burns.

There may also be associated with symptoms such as headache, jaw pain, earache, deafness, or pain on moving the jaw.

Risk factors for Trismus

Around 10-40 % of people receiving radiation to the head and neck region will develop Trismus. The severity of the condition varies with the placement of the radiation, the amount of radiation received, and the patient’s own ability to tolerate the treatment.

Radiation that affects the TMJ, the pterygoid muscles, or the masseter muscle, is most likely to result in Trismus. (4)

Patients who have been previously irradiated, and who are being treated for a recurrence, appear to be at higher risk of Trismus than those who are receiving their first treatment.

Some patients who have not received radiation treatment may develop Trismus secondary to scarring and edema after surgery.

How is Trismus diagnosed?

Your doctor will perform a thorough medical examination, especially looking for signs of oral cancer, bone, and joint abnormalities or any other abnormal tissues in your jaw that may lead to Trismus.

Your doctor will also perform the following tests:

  • Measure how wide you can open your mouth.
  • Ask about any recent dental treatments or procedures.
  • Ask about any possible injuries to your jaw.
  • Ask about the history of prior surgery or radiation therapy to your head and neck.
  • Order imaging studies such as CT scan or an MRI scan to help determine whether your Trismus is stemming from a problem with your joints or tissues.

Treatment for Trismus

It is better to start treatment early for Trismus for a higher chance at recovery. Trismus is more commonly a temporary problem. Some of the treatment options available are:

  • Use of a jaw-stretching device- a physical therapist will tell you which stretches to perform and how often. These devices help increase the mouth opening by 5-10mm. (5)
  • Medication- your doctor may prescribe a muscle relaxant, pain reliever, or anti-inflammatory medication.
  • Physical therapy that involves massage and jaw stretching. (6)
  • A change to a predominantly soft food diet until symptoms improve.

Managing Trismus at home

There are things you can do at home that can relieve Trismus or prevent it from worsening. You can try the following two or three times during the day:

  • Find the areas of your jaw that are painful, and moving your fingers in a circular motion, massage the area for about 30 seconds.
  • Move your jaw from left to right, hold for a few seconds, and then move it right to the left.
  • Move your jaw in a circular motion. Make five circles to the left and 5 to the right.
  • Open your mouth as wide as you can, holding the position to stretch it for a few seconds.
  • Stretch your neck, tuck your chin into your chest, and hold for 30 seconds. Then bring your head back and hold for another 30 seconds. Similarly, move your head to the left and then to the right. Finally, move your head in a circular motion.

Take away message

Trismus or lockjaw is a temporary condition, which responds well to both medication and physical therapy. Your dentist can advise you on the best ways to avoid developing Trismus.

In case you are going to start chemotherapy or radiation therapy, it is better to visit your dentist before that and let them know how your mouth is feeling.

It is best to follow your dentist’s directions regarding the prevention and management of Trismus.