Trismus: Classification, Causes, Symptoms, Diagnosis and Treatment

It is commonly associated with tetanus infection, but it can also be the result of some other causes.

Trismus is the medical term for ” jaw block, ” a condition that causes the muscles of the jaw, known as the muscles of mastication, to spasm or contract uncontrollably.

Those affected by tourism usually cannot open their mouth, which makes it difficult to eat, perform speech and maintain proper oral hygiene.

There are temporary and permanent cases of trismus development. However, most patients tend to fall into the former. The typical variation of the opening of the mouth falls in the range of 40 to 60 mm.

Similar to the amplitude of approximately two fingers to the width of three fingers, some variations were found between the sexes.

The classification of tourism

This can be called the distance between the upper and lower front teeth (incisors) when the mouth is completely open:

  • Living: 30 mm.
  • Moderate: 15-30 mm.
  • Grave: 15 mm.

A more precise definition of trismus would be the difficulty opening the mouth due to a muscle spasm due to an alteration in the trigeminal nerve.


Although this cranial nerve is responsible for several other facial functions, its alteration causes a limited mouth opening in cases of trismus.

What causes tourism?

The muscles of the mastication consist of the temporal, the masseter, the internal pterygoid, and the lateral pterygoid, and each one plays a vital role in allowing us to chew our food.

Damage to any of these muscles can cause limitations in the opening of the mouth and the inability to chew due to pain. This pain reflex is often referred to as “muscle protection.”

It develops when the muscle fibers cause pain when they stretch. The pain causes the muscles to contract, resulting in a decreased range of motion that the patient can not control.

The causes of trism include:


Maybe related to the teeth (odontogenic) or not related to the teeth (not odontogenic). The odontogenic infection can be of pupal, periodontal, or pericoronal origin.

Oral infections around the third molar are the most common. Severe oral conditions, if left untreated, often present with trismus.

Non-odontogenic infections include tonsillitis, tetanus, meningitis, parotid abscesses, and brain abscesses that lead to the development of trismus.


Fractures of the jawbones can cause a limited jaw opening with a degree of limitation that depends on the type of injury and the direction of the traumatic force.

The trauma can result from a sports injury or even a complex dental procedure, such as removing a tooth.

Accidental injuries that lead to external penetration of a foreign object can also cause trismus, but it is relatively rare.

Disorder of the temporomandibular joint. This disorder is characterized by unbearable pain or tenderness of the jaw.

We use our jaw muscles every day to chew our food, talk, and even breathe through our mouths. All these actions are based on a joint called the temporomandibular joint.

This sliding hinge can be the source of pain felt in the joint itself and the muscles that control the movement of the jaw.

The exact reasons for the development of TMJ disorders may be challenging to determine, but they may result from several factors, including genetics, arthritis, or jaw injury.

Drug therapy:

The side effects of some medications can lead to the development of trismus. Medications may include succinylcholine, phenothiazines, and tricyclic antidepressants.

Some of the most common causes related to drugs are considered.

Radiation therapy / chemotherapy:

The cells of the oral mucosa have a high growth rate. They are susceptible to the toxic effects of chemotherapy, which leads to the development of stomatitis, an inflamed or sore mouth.

This condition can cause severe discomfort, pain, trismus, and difficulty swallowing.

The use of radiotherapy can lead to the development of osteoradionecrosis, Bone death due to radiation, which can cause pain, trismus, pus formation, and occasionally lousy smell wounds.

Oral tumors and neoplasms:

Primary or secondary neoplastic disease in the epipharyngeal region, the parotid gland, the jaws, or the TMJ may cause trismus.

Fibrosis of the submucosal tissue causes whitening of the mucosa and can affect speech by restricting the tongue and soft palate movements.

Congenital / developmental causes:

The hypertrophy (enlargement) of the coronoid process that causes interference of the coronoids against the anteromedial edge of the zygomatic arch occasionally reports accompanying trismus.

Trismus-pseudo-camptodactyly syndrome is a rare condition that may also be associated with this development of trismus.

Symptoms of trism

The limitations with the opening of the mouth cause a series of additional complications. It can chew food well, which causes drastic changes in the diet, leading to inadequate nutrition.

The cause of your tourism will also bring additional presentations. The following are the most commonly observed trismus symptoms:

  • Fever (in infections).
  • Rigidity, intense or dull pain, sensitivity, or swelling in the chewing muscles.
  • Grid, cracks, clicks during movements of the lower jaw.
  • Decreased range of motion in the temporomandibular joint.
  • Reduced ability to chew, talk, sing, yawn, and brush your teeth.
  • Difficulty swallowing or choking.
  • Deviation of the jaw to the affected side.
  • Headache.
  • Difficult breathing


A complete medical history will be taken to evaluate any possible predisposing event that may have led to the development of trismus.

Your doctor may feel the need to request images in the form of a CT scan or an MRI.

Treatment for trism

Treatment will depend on the underlying cause and, in general, should be implemented promptly before the condition worsens.

Mild cases of pain and dysfunction can be managed with heat therapy, analgesics, muscle relaxants, and a soft diet, if necessary, until an exam can be scheduled.

These are the most common initial guidelines for the treatment of trismus. Heat therapy involves placing a warm, wet towel over the affected area for approximately 15 to 20 minutes every hour.

Medications such as aspirin and other anti-inflammatory drugs may be helpful in cases of trismus. For severe pain and discomfort, narcotic analgesics can be used at the discretion of the prescribing physician.

When the acute phase ends, patients are advised to begin physiotherapy to open and close the jaws.

Chewing gum without sugar is another way of providing lateral movement of the temporal-mandibular joint. A dentist should treat cases of infected and painful teeth.