Suffice it to say, if you woke up one morning and your jaw was locked shut, you’d be very frightened. That’s one of the symptoms of lockjaw, which is clinically known as trismus.
Every year I see many patients who experience that very thing. What’s worse, it can happen at any time and for seemingly unknown reasons. The first thing I’m asked is, “Why is this happening to me and what can I do to prevent it?”
Before I answer those questions, I want to explain how your jaw works. It is truly a miraculous joint.
Your jaw is essentially a hinge that is controlled by four muscles: the masseter, the temporalis, the internal pterygoid and the external pterygoid. The names may sound like extinct dinosaur species, but they are, in fact, very delicate muscles that perform the important job of opening and closing your jaw and moving it from side to side.
What Causes Lockjaw?
What causes lockjaw are jaw muscle spasms or when they become impaired, incapacitated, or shortened. It then becomes difficult or even impossible to open your mouth. That’s when the symptoms of lockjaw can occur.
(If you want to determine if your jaw is opening normally, try this test: open your mouth and insert three full fingers placed horizontally with your fingertips facing into your mouth. If they fit easily, you’re in good shape.)
8 Reasons That Lockjaw Symptoms Can Occur
Here are the most common reasons that someone can experience lockjaw symptoms:
1. Daytime Behavior Risk Factors
Your jaw muscles are just like most of the other muscles in your body in that when over-used they can fatigue and go into spasm which results in pain, limited motion, or both. If you’re a gym rat, you have probably experienced the same sensation after over-working a hamstring or calf muscle. You end up with limited motion, pain, or both. Your jaw muscles behave exactly the same way.
Many types of daytime behavior can cause jaw muscles to fatigue such as excessive gum chewing, prolonged contact between your upper and lower teeth, ceaseless nail-biting, and keeping your teeth clenched for long periods of time.
Prolonged tension in your upper neck can also cause your jaw muscles to shorten and make it impossible for you to fully open your mouth. Being under a tremendous amount of stress, feeling anger, discontent, worry, anxiety, or fear over a long period of time can compromise your jaw and neck muscles and precipitate the onset of lockjaw symptoms.
But millions of people chew gum, clench their teeth, and bite their nails without developing the symptoms of lockjaw. In the field of orofacial pain, we consider those behaviors risk factors – as opposed to being the cause of the problem.
2. TM Joint Problems
Your jaw joints (your TM joints) are literally the hinges that allow your top teeth and your bottom teeth to move independently of each other. Problems that arise in the TM joints can lead to jaw pain, jaw clicking, and lockjaw, to name just a few. Lockjaw symptoms in these cases are a result of pain, muscle tightening, spasms, or mechanical interferences in the hinge itself.
3. Jaw Trauma
Trauma (such as from an auto accident or sports mishap) that causes fracture, inflammation, muscle bruising, hematoma formation, a sprain in the TM joint, or a change in the joint’s anatomy can lead to lockjaw symptoms.
4. Cancer Therapy
Cancer therapy, such as radiation to address head or neck cancer, can cause jaw and neck muscles to become less flexible and lead to symptoms of lockjaw.
5. Head or Neck Tumors
Certain tumors in jaw muscles and/or in the TM joint could cause lockjaw symptoms. But we also know that tumors in the throat, larynx, pharynx, thyroid, parotid gland, or ear can also be the culprit.
Tetanus is a bacterial infection characterized by muscle spasms that most often start in the jaw then progress to the rest of the body. Thankfully, tetanus-caused lockjaw is rare today in the United States because of the Tetanus vaccine.
7. Other Infections
Other types of infections such as those associated with impacted wisdom teeth, infected tonsils, or infected salivary glands can also cause symptoms of lockjaw.
8. Dental Work
Dentists often need to give what is called a mandibular block injection with local anesthetic in order to comfortably treat a lower molar tooth or remove a lower wisdom tooth for instance. Mandibular block injections are performed millions of times a day with no problems, but on a rare occasion, we see a patient who wakes up unable to open his or her mouth sometimes with jaw pain within a few days after the injection. This is usually the result of trauma to a nearby muscle, bleeding, too much anesthetic, or a slow-developing infection.
How Lockjaw Symptoms Are Diagnosed
First, your doctor must be able to find the cause or risk factors associated with your lockjaw symptoms. Since all lockjaw situations are accompanied by some degree of limited jaw motion, the degree of limitation is one of the keys to finding the reason for it in the first place. The most important element in getting to a correct diagnosis is to tell your doctor what happened before your symptoms emerged. Some lockjaw symptoms include pain and soreness. Sometimes there is no pain at all…just restricted motion. A clicking jaw joint that suddenly doesn’t click anymore can be a clue, too. The evaluation can include x-rays, a CAT scan, or an MRI of your TM joints, head, and/or neck depending upon what clues are in your history and exam.
How Lockjaw Is Treated
Your doctor will develop a treatment plan that’s tailored for you based upon the reasons for your lockjaw symptoms. The plan may include jaw exercises, warm moist heat applications, anti-inflammatory medications and /or antibiotics for a short period of time, and/or physical therapy. It’s important to be patient. A full recovery can take several months.
Note: If the lockjaw symptoms are a result of trauma, radiation, tumors or other more serious causes, some level of jaw motion deficit may be permanent.