Exteroceptive Suppression Of The Masticatory Muscles In Patients With Tension-type Headache And Migraine

Objective:To investigate the value of the trigeminal exteroceptive suppression (ES)of temporalis and masseter muscles on tension-type headache(TTH)and migraine using electromyography(EMG).Methods:The examinations of ES were accomplished using EMG in 30 patients with TTH,20 migraineurs and 30 normal volunteers.The early(ES1)and late (ES2)ES periods of activities of the bilateral masticatory muscles were evoked by electrical stimulation of the infraorbital region with increasing intensity at a rank of 5mA,when subjects were clenching teeth with the maximal strength.We analysed the frequency,degree of suppression,onset latency and duration of ES of temporalis and masseter muscles,we also studied the correlation between them and the intensity of electrical stimulation.Results:1.The frequency,degree of suppression,onset latency and duration of ES1 from each subject were stationary,which there was no correlation with the intensity of electrical stimulation.The latency and duration of ES1 were respectively 12.6～13.3ms and 13.5～16.1ms.There was no significant difference of ES1 latency and duration among different groups(P＞0.05).2.The frequency of ES2 was lower in TTH group than that in control and migraine groups(P＜0.05).3.The degree of suppression of ES2 tended to increase with increasing intensity of stimulation,but to be relative stable at 20～40mA intensity of stimulation.Some distinctive waves with highly suppressive degree were evoked in 70%(14/20) patients with migraine.4.ES2 latency and duration of bilateral masseter muscles were respectively prolonged and shortened compared with those of temporalis muscles (P＜0.05).There was no significant difference of the ES2 latency and duation between the both side of masticatory muscles.5.The mean ES2 latencies of temporalis and masseter muscles were respectively 61.3ms and 56.3ms in TTH group,54.1ms and 49.8ms in migraine group,52.8ms and 49.0ms in control group.The mean ES2 durations of temporalis and masseter muscles were respectively 25.8ms and 26.5ms in TTH group,27.9 ms and 31.3ms in migraine group,30.4ms and 33.2ms in control group.ES2 latencies were prolonged and the durations were shortened in TTH group than those in migraine and control groups(P＜0.05).There was no significant difference of the ES2 latencise and duration between the migraine and control groups(P＞0.05).Conclusion.The reduction or abolishment of ES2 in TTH group suggests deficient activity of the central inhibitory interneurons.Distinctive waves with highly suppressive degree in migraine group suggest overactivity of the interneurons.The findings of the trigeminal ES of masticatory muscles provide evidences for the dysfunction of central pain modulation in patients with TTH and migraine,ES might contribute to do the electrophysiological research into TTH and migraine.