Tetanus-induced Trismus: Improvement on a Daily Basis

An 85-year-old man, who usually grew vegetables with his bare hands, presented to our hospital with the inability to open his mouth to eat. A physical examination revealed trismus and masseter muscle tenderness. No apparent wound was observed. The findings of orofacial computed tomography, brain magnetic resonance imaging, and a blood analysis were normal. A surface electromyogram of the masseters with mechanical tap to the jaw showed the absence of the masseteric silent period and continuous background muscle activity (1) (Picture 1). The patient was clinically diagnosed with tetanus and treated with human tetanus immunoglobulin and intravenous metronidazole. The patient’s trismus gradually improved from three days after admission (Picture 2), and he could eventually eat. Although the differential diagnoses of trismus are numerous, it is a typical symptom of tetanus (2). This case illustrates the importance of