Trismus is a condition of restricted opening of the mouth. The term was initially used in the setting of tetanus. 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 an inability 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. 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 painful restriction in opening the mouth due to a muscle spasm, however it can also refer to limited mouth opening of any cause. Another definition of trismus is simply a limitation of movement.
Normal mouth-opening ranges from 35 to 45 mm. and normal protrusive movement is approximately 10 mm. 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 Greek word trigmos/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).
- Myositis ossificans.
- Inflammation of muscles of mastication.
History
Historically, the term trismus was used to describe the early effects of tetany, also called "lockjaw".