Electromyographic evidence of reduced muscle activity when ULF-TENS is applied to the V-th and VIIth cranial nerves

The object of this study was to determine if the resting muscle activity of TMD patients with measured hyperactivity (EMG(ave) > 2.0 microvolts) could be reduced by the application of ULF-TENS (Ultra-Low-Frequency-Transcutane ous Electrical Neural Stimulation) [(BioTENS) BioResearch, Inc. Milwaukee, WI]. Twenty-nine patients with resting muscle hyperactivity and ten without resting muscle hyperactivity were selected from a series of 124 consecutiv ely diagnosed TMD patients. Electromyographic records were taken bilaterall y (with the mandible at rest) from the superficial masseter, anterior tempo ralis, anterior digastric, and posterior temporalis muscles before and afte r the application of ULF-TENS. The EMG data were averaged. For the 85 muscl es that were found initially to exceed the usual cutoff of 2.0 microvolts, means and standard deviations were calculated. The "before TENS" levels wer e: mean = 3.353 +/- 1.44227 and the "after TENS" values were: mean = 1.844 +/- 0.92421. Using a student t-test, we found the difference between the be fore and after levels significant (p < .0005). Additionally, means and stan dard deviations were calculated for each muscle (Ta, Mm, etc.) separately a nd also found to be significantly different (before Vs after TENS). In thes e "hyperactive" patients, the nonhyperactive muscles were also pooled, the means calculated before (mean = 1.21 +/- 0.456) and after (mean = 1.00 +/- 0.345) TENS and found to be significantly different (p < 0.01). For the ten patients exhibiting no muscle exceeding the 2.0 microvolt cutoff (mean = 1 .08 +/- 0.415), no significant change tin levels) was observed after ULF-TE NS (mean = 0.96 +/- 0.359; p > 0.88); however, when we calculated the "pair ed difference," we found a significant reduction, albeit very slight, in th ese patients' muscles, too. We conclude that ULF-TENS has an activity-reduc ing effect on the resting EMG levels of both hyperactive and relaxed muscle s. It also appears that while the > 2.0 microvolt cutoff is useful for iden tifying patients that are hyperactive at rest, it does not identify complet e relaxation of masticatory muscles.