口腔咽頭領域の悪性腫瘍と開口困難

抄録

Trismus, by which we understand a tonic contraction of the jaw-closing muscles, has received broader application in usage, including all conditions characterized by inability to open the mouth adequately. Recognition of trismus and confirmation by a measured interincisal opening of less than 35 mm enables the clinician to focus rapidly on the differential diagnosis of trismus. Malignant diseases in the oral cavity and pharynx may cause trismus either by growing directly into the masticator muscles or the temporomandibular joint (TMJ), or by spasm of the muscles initiated by a response of somatic afferent fibers as a result of tumor growth or concomitant stomato-pharyngitis. Moreover, fibrosis may arise in the muscles or at the capsule of the TMJ after irradiation.
The charts of 60 patients with malignant tumors in the oro-pharyngeal region seen and treated at Tokyo University Branch Hospital between April 1983 and March 1991 were reviewed. Nine of these patients had trismus. Two out of the nine showed the sign at the time of first examination. Three patients developed trismus due to the tumor extension. In four others, trismus was considered to be a result of irradiation.
In most cases of trismus other than radiation-induced, CT revealed no evidence for direct invasion into the masticator space by the tumor when trismus occurred, which suggests that trismus was caused either by reflex spasm or by microinvasion of muscles too small to be visible in CT scans. However, tumors tend to extend into the masticator space afterwards. Thus, trismus may be an early sign of masticator space involvement.