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Lockjaw: Causes, Symptoms, and Treatment for Trismus

Lockjaw, also known as trismus, is a jaw muscle spasm that makes it hard to open your mouth and swallow. It can cause complications when ignored. Read on to learn why your jaw locks and find out how to treat lockjaw.

Trismus (or lockjaw) is the contraction of the muscles used to chew. In this disorder, your chewing muscles become rigid, reducing their range of motion. This makes it hard or impossible to fully open your mouth.

Normally you can open your jaw wider than 1.18 to 1.57 inches (30 to 40 millimeters). In trismus, your mouth may not be able to open more than 0.78 inches (20 millimeters).

Doctors use three levels of severity to describe trismus:

  • Mild — The range of motion of your jaw is decreased, but you are still able to eat.
  • Moderate — The range of motion of your jaw is more decreased, requiring you to eat purees, soft foods, and small bites.
  • Severe — The range of motion of your jaw is severely decreased, and you’re not able to eat or drink.

Lockjaw can have serious health implications because of the reduced movement of the mouth. These include reduced nutrition because you’re not able to chew, bad oral hygiene, and trouble speaking. Radiation therapy to the neck and head area can sometimes cause trismus along with trouble swallowing.

One of the most common symptoms of lockjaw is trouble opening your mouth. For people with cancer, lockjaw often results from the formation of scar tissue due to surgery or radiation therapy, damage to the nerves, or a combination of other factors. People who have had a stroke may not have a properly functioning central nervous system, which can also cause lockjaw. 

Lockjaw tends to get worse gradually, and some people may not notice it until it becomes severe. You can take the “three-finger test” to find out whether you have trismus or not. If you can fit three fingers between your incisors (front teeth), then the range of motion of your jaw is normal. If you aren’t able to insert three fingers, then you may have lockjaw.

Some other symptoms of lockjaw are:

  • Pain in the jaw
  • Headache
  • Deafness
  • Painful jaw movement
  • Earache

Trismus can occur as a result of damage to the nerves and/or muscles that are responsible for chewing and closing and opening the mouth. Some conditions that can cause trismus are:

  • Dislocation or fracture of the lower jaw bone
  • Injury of the temporomandibular joint
  • Direct injury or trauma to the chewing muscles
  • Fibrosis (hardening) of soft tissue
  • Osteoarthritis
  • Scleroderma (an autoimmune disease in which the connective tissues harden and tighten)
  • Rheumatoid arthritis
  • Osteomyelitis (an infection of the bone) of the lower jaw bone
  • Pyogenic arthritis (infectious arthritis)
  • Tonsillitis
  • Peritonsillar abscess (collection of pus near the tonsils)
  • Tetanus
  • Mumps
  • Parotid (salivary gland) abscess
  • An odontogenic abscess (dental abscess)
  • Trismus-pseudocamptodactyly syndrome (a rare inherited disorder in which the person has short tendons and muscles, resulting in limited movement of the mouth, legs, and hands)
  • Pierre-Robin sequence (a condition in which a baby is born with a smaller than usual lower jaw, difficulty breathing, and a tongue that falls back in their throat)
  • Tumors of the parotid gland
  • Pharyngeal cancer
  • Status epilepticus (continuous seizure that lasts for longer than 30 minutes)
  • Parkinsonism
  • Poisoning from phenothiazine or strychnine
  • Adverse effects of certain medicines (for instance, phenothiazines, tricyclic antidepressants, and metoclopramide)
  • Respiratory alkalosis (an acid–base imbalance from hyperventilation)
  • Hypomagnesemia (low levels of serum magnesium)
  • Hypocalcemia (low levels of serum calcium)
  • Radiotherapy for cancer of the neck and head
  • Perioperative inflammation (inflammation that occurs around the time of surgery)

Prompt treatment of lockjaw can help minimize or prevent further complications.

Your doctor will diagnose the condition and may suggest treatment depending on the cause of trismus. They may also refer you to a physiotherapist or speech therapist to help manage the symptoms of lockjaw. Your doctor may suggest or prescribe pain relievers such as nonsteroidal anti-inflammatory drugs, muscle relaxers, or heat therapy to treat trismus.

You may also need stretching exercises if your trismus was caused by surgery or an injury, especially if you’ve been having symptoms for more than one week. These exercises usually involve trying to open your mouth against resistance. You have to do them multiple times per day.

For chronic trismus from ongoing radiotherapy or fibrosis, your doctor may recommend intense physiotherapy. Physical therapy may include exercises for range of motion, electrotherapy, and mobilization. Your doctor may recommend physical therapy with or without medication.

When applied multiple times a day, passive motion (movement done by another person) has been found to be more effective than static stretching (stretching in a comfortable but challenging position for a certain period of time). According to recent clinical research from the University of Pittsburgh, passive motion can result in a significant reduction in lockjaw pain and inflammation.

Specific rehabilitation devices for jaw motion may be especially helpful. Your doctor may suggest such a device if other treatments for your lockjaw aren’t working.

Your doctor may suggest extraoral or intraoral surgeries or minimally invasive procedures using endoscopy to treat your lockjaw. During surgery, the surgeon may remove the temporalis muscle (one of your chewing muscles) from its point of insertion. This can help improve the joint’s range of motion because this is the muscle that helps close your mouth.

Trismus is a common side effect of receiving treatment for cancer of the head and neck. Unfortunately, doctors don’t yet know how to prevent or treat this particular side effect of cancer treatment safely and effectively. However, not everyone receiving radiation therapy to their neck and head area will develop lockjaw.

Trismus can significantly affect your routine, and if you know you’re prone to lockjaw, it is best to begin exercises before you develop symptoms. Your doctor can suggest exercises to prevent and manage it. They can also help you find out whether your insurance provider will cover the cost of your treatment.






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