Trismus is a restriction in the ability to open the mouth. Trismus can occur 
following trauma, surgery, radiation therapy, infection, inflammatory diseases, 
temporomandibular disorders (TMD) or less commonly as a result of malignancy. 
Following two cases of delayed diagnosis of carcinoma presenting with features 
of TMD to a specialist clinic, a checklist was developed for completion in cases 
of trismus, to alert the clinician to suspicious features suggesting a possible 
non-TMD cause. The use of this checklist, together with an increased awareness, 
has improved early recognition of atypical features in patients presenting with 
trismus and has contributed to the early diagnosis of a further case of 
malignancy presenting to this clinic. This article discusses the presentation of 
malignancy with trismus, the relevance of imaging in these cases, and the 
implementation of a checklist to reduce the risk of future misdiagnosis.