Significance of Time-Domain Measurements of Heart Rate Variability in Burning Mouth Syndrome

Burning mouth syndrome (BMS) is characterized by oral burning or painful sensations without pathological changes; its real cause is unknown. We previously reported that autonomic lability was probably associated with the pathogenesis of BMS based on the results of frequency analysis of heart rate variability (HRV). HRV is composed of time and frequency domains, although the significance of the time-domain measurements of HRV in BMS has not been discussed. In this study we assessed the significance of the timedomain measurements, particularly in relation to autonomic lability. Twenty-two patients received stellate ganglion near-infrared irradiation (SGR), and the response to SGR was examined by time-domain measurements. No significant difference in the time domain was found between patients in whom SGR was effective and those in whom SGR was ineffective for BMS. We proposed several new parameters that were defined as the differences in previously established parameters between just before and after irradiation. Two of these parameters, the differential mean heart rate (D Mean HRT) and differential root mean square of successive NN interval differences (D RMSSD), reflected the relieving effects of SGR. The time-domain measurements revealed that autonomic lability, particularly parasympathetic modulation, was associated with BMS, because the parameters are considered indicative of parasympathetic responsiveness to SGR. Therefore, time-domain measurements are very useful for follow-up of BMS and for determination of the therapeutic efficacy of SGR.