Ultrasonic diagnosis of masseteric hypertrophy.

Masseteric hypertrophy may present a diagnostic dilemma, its confirmation frequently being by exclusion of other conditions. The literature relating to this syndrome is reviewed. A study to confirm the suitability of ultrasound in diagnosis, and to establish a normal range, is described. Sixty-two masseter muscles were measured using a standardized technique and the derived normal range for transverse dimension was 8.5-13.5 mm. Three instances of clinically diagnosed masseteric hypertrophy were examined; in each case measured transverse masseteric dimension was significantly greater than the normal range. Direct ultrasonic measurement of masseteric bulk should replace computed tomography as the definitive investigation in suspected cases.