What Is Lockjaw?

Lockjaw (trismus) is when the jaw muscles spasm and affect jaw movement. If you develop this condition, your jaw may be "frozen" in position and you might not be able to open your mouth wide.

Lockjaw can be painful and cause complications such as choking. Medication side effects, cancer treatment, and tetanus are a few of the possible causes.

This article explains the symptoms, causes, diagnosis, and treatment of lockjaw.

Symptoms of Lockjaw

Lockjaw affects the whole jaw and is usually experienced equally on both sides. It can occur suddenly and reaches peak intensity in a matter of hours.

While an inability to open the mouth fully is the most common symptom of lockjaw, several others can occur as well. Within just a few hours, lockjaw results in:

• Headaches
• Jaw pain
• Earaches

Because you can't control your mouth, your speech may be difficult for others to understand. In addition, you can have trouble swallowing.

After about a day, lockjaw can affect your oral health because you can't swallow saliva. This can cause:

• Xerostomia (dry mouth)
• Mucositis (sore and inflamed mouth)

Complications

Lockjaw that lasts for longer than a few days can affect your overall health. Complications of persistent lockjaw include:

• Tooth decay and ulcers in your mouth due to an inability to effectively brush your teeth and floss
• Bruxism (teeth grinding), which can cause your tooth enamel to wear away and even cause your teeth to crack
• Malnutrition due to difficulty eating
• Muscle stiffening, which does not respond to treatment as quickly as a muscle spasm

Causes

Lockjaw occurs because of a muscle spasm, which is when a muscle remains in its active position and cannot relax. The muscle spasm that occurs with lockjaw can result from many things.

For example, it might occur due to an injury to the muscle, nerve, bone, tendon, or ligament. It may also arise from health conditions, infections, and medications.

Temporomandibular Joint (TMJ) Disorders

Your temporomandibular joint (TMJ) is located at the sides of your face, below your eyes, and toward your ears. This joint is where the muscles, bones, tendons, and ligaments that control your jaw meet.

TMJ disorders commonly result in lockjaw. TMJ can develop for multiple reasons, including:

• Arthritis
• Inflammatory disease
• Facial trauma

Infections

Infections around your mouth or jaw muscles, such as a peritonsillar abscess, can affect the jaw's movement. When this happens, lockjaw can occur.

In rare instances, your nerve or muscle can become permanently damaged from an infection. If it does, you may be more likely to experience recurrent episodes of lockjaw.

Medication

Some medications can affect nerve function and lead to lockjaw. The most common culprits are anti-nausea medications, such as Reglan (metoclopramide) and some antipsychotic medications.

More rarely, anesthetics can cause a rare complication called malignant hyperthermia. This complication is a severe reaction involving high body temperature and rapid heart rate. In addition, it can involve muscle spasms, including lockjaw.

Cancer

Cancer and some cancer treatments (surgery, radiation) can cause injuries to parts of the jaw that control movement. The following are risk factors for developing lockjaw:

• Head or neck cancer
• Surgery for head or neck cancer
• Radiation treatment for head or neck cancers

If you have head or neck cancer or have had treatment for these types of cancers, you have about a 30% chance of developing lockjaw.

Tetanus

Tetanus occurs from exposure to a life-threatening neurotoxin released by Clostridium tetani, a bacterium commonly present in the environment.

Tetanus toxin can cause muscle spasms. These spasms may affect several muscles throughout the body, including:

• Heart muscles
• Chest muscles (impairing breathing)
• Facial muscles, including those of the jaw
• Any voluntary muscles in the body

Tetanus is a significant risk factor for lockjaw—so much so that those with tetanus almost always experience it. In fact, lockjaw used to be called tetanus.

However, tetanus is extremely rare in most parts of the world because immunizations and booster shots that protect against the infection are routine.

Other Medical Conditions

Hypocalcemia (low calcium levels) is another common cause of lockjaw. This complication can sometimes occur during thyroid surgery.

Sometimes, nerve or muscle diseases can cause muscle spasms. For example, stiff person syndrome, a rare autoimmune disorder, can cause spasms in any voluntary muscle.

Diagnosis

Doctors diagnose lockjaw based on your medical history and a physical examination.

However, the effects of lockjaw can make it difficult for you to explain your symptoms to your medical team. Most people have to describe their medical history by writing it down.

Physical Examination

Typically, people can open their mouths between 35 to 55 millimeters (mm) or 1.4 to 2.2 inches wide. However, if you have lockjaw, you may only be able to open your mouth as much as 35 mm (1.4 inches). That's less than three fingers in width.

In addition, if you have lockjaw, your doctor will look for the following:

• Your ability (or inability) to close your mouth all the way
• Trouble moving your jaw
• Stiffness and tightness of your jaw muscles
• Clenched teeth
  

Tests

If there is a concern that you could have an injury, infection, or tumor affecting your mouth, face, or jaw, you may need diagnostic testing.

Imaging studies can often identify lesions in and around the jaw. They might include:

• X-rays
• Computerized tomography (CT)
• Ultrasound
• Magnetic resonance imaging (MRI)

In some instances, you may need to have a piece of a tumor removed so that it can be examined more closely. This is called a biopsy.

Treatment

Treatment for lockjaw often involves medication and physical therapy. Any underlying problems often require additional treatment.

For example, if you also have an infection, your treatment will include antibiotics.

Specialists who treat lockjaw include:

• Otolaryngologists (ENTs)
• Dentists
• Oral surgeons

Spasm Relief

Oral and injected muscle relaxants are typically helpful. Common examples of oral medications that relax muscles include:

• Flexeril (cyclobenzaprine)
• Skelaxin (metaxalone)

These medications may cause side effects such as drowsiness.

Targeted injections, including botulinum toxin (Botox) or anti-inflammatory steroids, can relax the muscle, relieving the spasm.

Injections do not cause the kind of body-wide side effects seen with oral medications.

Physical Therapy

In addition to medical management, you may need physical therapy or speech therapy. Your therapist may also suggest at-home exercises so you can improve control of your jaw muscles.

Treating the Underlying Problem

What this might involve varies, given the range of medical conditions that can cause lockjaw. Treatment may include:

• Oral or intravenous (IV) antibiotics (for infections)
• Anti-inflammatory treatment (for TMJ)
• Radiation or surgery (for tumors)

If radiation therapy or surgery is the cause of your lockjaw, then physical therapy might be the most effective treatment approach. Know, however, that longstanding lockjaw after radiation therapy can be very challenging to reverse.

Summary

Lockjaw, as the name suggests, is a condition where the muscles in the jaw affect its movement. The mouth isn't able to open as widely as usual, which can affect speech and swallowing.

Infections, health conditions, injury, and reactions to medications can cause lockjaw.

Treatment is aimed at relaxing the muscles and getting the moving normally again, as well as addressing the root cause. Physical therapy and medication are common components of a treatment plan.

A Word From Verywell

If you have experienced lockjaw, you may be at risk of developing it again. So, it is important to discuss prevention with your healthcare provider.

Preventative strategies may include avoiding medications that trigger it, getting treatment for TMJ, and maintaining regular exercise of your jaw muscles.

But, most importantly, if you notice the symptoms, seek medical attention promptly to avoid complications.