The Masseter Reflex: Postprocessing Methods and Influence of Age and Gender

Objectives: Normative values of the masseter reflex are scarce. We studied the latencies, amplitudes and side differences of the masseter reflex in 105 healthy volunteers between the ages of 5 and 78 years. Methods: Latencies were calculated as the mean of 10 single sweeps and, simultaneously, measured from the summation curve. Short-term reproducibility was determined in 33 volunteers by retesting the reflex after 1 week. Results: There was a positive correlation between age and latencies and a negative correlation between age and amplitude. Maximal normal latencies were 8.3 ms for men and 7.9 ms for women in the age group below 50 years and 9.1 and 9.2 ms for the age group above 50 years. Latency differences between the right and left sides of >0.4 ms for subjects aged below 50 years and >0.5 ms for subjects aged above 50 years exceeded the 95% confidence interval. Amplitudes did not depend on gender. Calculated as a percentage of the side with higher amplitude, differences above one third could be accepted as abnormal. Conclusion: The masseter reflex appears to be a stable and robust clinical test, if age and gender differences are taken into account.