Trismus in head and neck cancer patients

Trismus, a restricted mouth opening, is common among head and neck cancer patients. Head and neck cancer patients experience trismus as one of the three most burdensome side-effects after their cancer treatment. Patients are most likely to experience a restriction in functioning if the mouth opening is 35 millimeter or less.
The development of trismus is most likely, when the mouth opening before treatment is small already, when risk structures (such as the masticatory muscles and the temporomandibular joint) are affected, and when the treatment is extensive (for instance a combination of treatment modalities or a high radiation dose) . Especially during the first six to twelve months after cancer treatment, the chance of developing trismus is high.
To prevent or treat trismus, exercise therapy using stretching devices (such as the TheraBite® Jaw Motion Rehabilitation System™ and the Dynasplint Trismus System®) is often given. However, it seems that exercise therapy using these stretching devices is challenging, because of negative side-effects of stretching, the intensive and burdensome exercise protocol, and limitations of the stretching devices.
In order to improve therapy for trismus or to prevent trismus in the future, factors negatively influencing mouth opening should be minimized, and the effectiveness of therapy for trismus should be optimized.