Dr. Adams' Alabama Headache Blog

Bilateral Surface electromyography was performed to establish norms on 200 Temporomandibular Dysfunction Syndrome patients (149 females and 51 males) ranging from 19 to 58 years of age. Electrode placements were over the masseter and anterior temporalis muscles of seated patients. Peak uV values were recorded under the following conditions: relaxed-dissoccluded (RD), swallow (PS), first contact of habitual bite (CH) and maximum forced bite in habitual, without causing or increasing pain (FB). Rather than right versus left, all analysis was based on lower masseter reading in uV. Mean RD was 2.80 for the lower and 5.43 for the higher side for masseter and 3.21 and 5.68 for temporalis. For CH the masseter means were 3.99 and 6.70 and for temporalis 8.33 and 4.96. Analysis of the more active conditions revealed two patterns of readings. In one pattern, the higher uV value for both masseter and temporalis occured on the same side (unilateral) while in the other, the higher masseter value was on one side while the higher temporalis was on the opposite side (crossover). In PS, masseter means were 7.7 and 10.0 while temporalis means were 10.3 and 6.2. In the FB condition 104 patients showed a unilateral pattern: masseter 61.6 and 98.2, temporalis 135.0 and 104.3. In the FB more than half the sample (108) could not generate more than 50 uV in the lower masseter reading. TMD patients show up to 50% difference in EMG activity in mandibular maneuvers. Two bite patterns, unilateral and crossover were found to be almost equally distributed in this patient population.