Risk structures for radiation-induced trismus in head and neck cancer

Treating head and neck cancer (HNC) is challenging as the tumors are located in a critical area where many essential functions originate. Amongst the late appearing side effects after radiotherapy (RT) for HNC, restricted mouth opening (trismus) occurs in more than one third of patients and have been described as persisting or even worsening five years after completed RT [1–3]. Trismus can lead to difficulties in eating, chewing, maintaining oral hygiene, and potentially to malnutrition and weight loss [2–6]. Irradiation of the temporomandibular joint (TM joint) and muscles of mastication, especially doses to the masseter and the pterygoid muscles, have been reported to be associated with radiation-induced trismus [7–11]. However, available data diverge as to which anatomical structure is more critical for trismus after RT in HNC. The aim of this prospective study was, therefore, to investigate if the use of both objectively and subjectively determined trismus can shed further light on this issue.