Activity of masticatory muscles in subjects with different orofacial pain conditions

Abstract

The existence of a pathophysiological link between tonic muscle activity and chronic muscle pain is still being debated. The purpose of this retrospective, controlled study was to evaluate the electromyographic (EMG) activity of masticatory muscles in subjects with different orofacial pain conditions. The temporal and masseter EMG activity at rest and the masseteric reflex were recorded in two groups of patients with either myofascial pain (n=33) or neuropathic pain (n=20), one group of non-pain patients with disc derangement disorders (n=27) and one control group of healthy, asymptomatic subjects (n=32). The EMG activities of both muscles at rest were significantly higher in the pain patient groups compared to the asymptomatic control group. There was no significant difference between the disc derangement disorder group and the control group. The masseteric reflex amplitude was reduced in all patient groups when compared with the control group. In pain patient groups, the increased EMG activity at rest and the reduction of the masseteric reflex amplitude were equally distributed in the pain and non-pain sides. In addition, subjects presenting with bilateral pain showed higher EMG activity at rest than those with unilateral pain. These results suggested that the modulation of muscle activity was not the direct consequence of a peripheral nociceptive mechanism and seemed to indicate that a central mechanism was at work. The contrast between the increased EMG activity at rest and the reduction of the masseteric reflex amplitude may reflect modulations of motoneurones that differed in tonic versus phasic conditions in chronic pain patients.

GABAB receptors in the NTS mediate the inhibitory effect of trigeminal nociceptive inputs on parasympathetic reflex vasodilation in the rat masseter muscle

“…It has been reported that orofacial pain modulates the activity of the jaw muscles (2) and jaw-stretch reflex (2,30,37,41), suggesting that changes in the functional properties of the jaw muscles mediated by trigeminal nociceptive inputs play an important role in the development of functional disorders of the masticatory system, including temporomandibular disorders. The hemodynamics in skeletal muscles, including jaw muscles, are widely recognized as one of the most important factors for maintaining muscle function (8).…”

Influence of craniomandibular and cervical pain on the activity of masticatory muscles in individuals with Temporomandibular Disorder

“…Some studies (5,7,9,10) have shown that patients with TMD, compared to asymptomatic patients, showed alterations in the activity of the masticatory muscles during chewing. However, the cited studies are not conclusive.…”

Electrical Activities and Pressure Pain Threshold in Oral Contraceptives Users and Nonusers

“…Since oral contraceptives are being suggested to increase pain and risk of TMD, [11] [12] the present study intended to evaluate the influence of oral contraceptive intake and menstrual cycle on the electrical activity and pressure pain threshold from anterior temporal and masseter mus-cles. A number of studies used rest position to analyses alterations in muscle electrical activity [21]- [23] [25] [26]. As our study was performed with asymptomatic women, we did not find any variation in electrical activity at rest position of oral muscles PPTs during different phases of the menstrual cycle.…”