Abstract

Trismus, also called lockjaw, is reduced opening of the jaws (limited jaw range of motion). It may be caused by spasm of the muscles of mastication or a variety of other causes. Temporary trismus occurs much more frequently than permanent trismus. It is known to interfere with eating, speaking, and maintaining proper oral hygiene. This interference, specifically with the patient's ability to swallow properly, results in an increased risk of aspiration. In some instances, trismus presents with altered facial appearance. The condition may be distressing and painful for the patient. Examination and treatments requiring access to the oral cavity can be limited, or in some cases impossible, due to the nature of the condition itself.

Definition

Trismus is defined as difficulty in opening the mouth due to a muscle spasm resulting from a disturbance in the trigeminal nerve, however it can also refer to limited mouth opening of any cause. Another definition of trismus is simply a limitation of movement. Historically and commonly, the term "lock jaw" was sometimes used as a synonym for both trismus and tetanus.

Normal mouth-opening ranges from 35 to 45 mm. Males usually have slightly greater mouth opening than females. (40–60 mm, average of 35 mm). The Normal Lateral movement is 8-12mm, and normal protrusive movement is approximately 10mm. Some have distinguished mild trismus as 20–30 mm interincisal opening, moderate as 10–20 mm and severe as less than 10 mm.

Trismus is derived from the Irish word "trismos" meaning "a scream; a grinding, rasping or gnashing"

Differential diagnosis

Traditionally causes of trismus are divided into intra-articular (factors within the temporomandibular joint [TMJ]) and extra-articular (factors outside the joint, see table).

Differential diagnosis | Extra-articular causes | Trauma

Fractures, particularly those of the mandible and fractures of zygomatic arch and zygomatic arch complex, accidental incorporation of foreign bodies due to external traumatic injury.

Treatment: fracture reduction, removal of foreign bodies with antibiotic coverage

Differential diagnosis | Extra-articular causes | Tumors and oral care

Rarely, trismus is a symptom of nasopharyngeal or infratemporal tumors/ fibrosis of temporalis tendon, when patient has limited mouth opening, always premalignant conditions like oral submucous fibrosis (OSMF) should also be considered in differential diagnosis.

Differential diagnosis | Extra-articular causes | Drug therapy

Succinyl choline, phenothiazines and tricyclic antidepressants causes trismus as a secondary effect. Trismus can be seen as an extra-pyramidal side-effect of metoclopromide, phenothiazines and other medications.

Diagnostic approach

X-ray/CT scan taken from the TMJ to see if there is any damage to the TMJ and surrounding structures.

Treatment

Treatment requires treating the underlying condition with dental treatments, physical therapy, and passive range of motion devices. Additionally, control of symptoms with pain medications (NSAIDs), muscle relaxants, and warm compresses may be used.

Splints have been used.

History

Historically, the term trismus was used to describe the early effects of tetany, also called "lock jaw".