The trigeminocardiac reflex is a rare occurrence in patients undergoing maxillofacial surgery, with a reported incidence of 1-2%. Clinical signs and symptoms include bradycardia, nausea, with further stimulation potentially leading to cardiac dysrhythmias, ectopic beats, atrioventricular blocks and asystole. Most maxillofacial procedures, including temporomandibular joint procedures, are considered low risk. We report the first case of a tender temporomandibular joint synovial cyst whose management was complicated by severe trigeminocardiac reflex resulting in asystole. We suggest that in such cases communication between surgeons and the anaesthesia team is of paramount importance and informing the anaesthetist intraoperatively prior to the manipulation of the capsule or temporomandibular joint meniscus is recommended in the prevention or successful treatment of this condition.