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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The exteroceptive suppression periods (ES) in human jaw-closing muscles can be conditioned by a wide range of somatosensory stimuli and cognitive states. The aim of this study was to examine the effects of tonic experimental jaw-muscle pain versus remote muscle pain on the short-latency (ES1) and long-latency (ES2) reflex in the jaw-closing muscles. Twelve healthy subjects participated in the first experiment with jaw-muscle pain. In random order 5% hypertonic or 0.9% isotonic saline was infused into the left masseter muscle for 15 min. The pain intensity was scored continuously by the subjects on a 10-cm visual analogue scale (VAS). Electromyographic (EMG) activity was recorded bilaterally from the masseter and temporalis muscles during the pre-infusion, early phase of infusion (from 120 to 480 s), late phase of infusion (from 540 to 900 s) and post-infusion. An electrical stimulus was delivered to the skin above the left mental nerve (ipsilateral to the painful muscle) to evoke the ES in the contracting jaw-closing muscles. Ten healthy subjects participated in experiment 2 which was as identical to experiment 1 except that the electrical stimulus was delivered to the right mental nerve (contralateral to the painful muscle). Nine healthy subjects participated experiment 3 where remote muscle pain was induced in the left tibialis anterior muscle. In experiment 1 painful infusion of hypertonic saline caused a significantly later onset latency of ES2 in the left masseter muscle during the late phase of infusion compared to pre-infusion values (P < 0.05). The duration of ES2 in the same muscle was significantly shorter during the late infusion phase compared to pre- and post-infusion values (P < 0.05) and the degree of suppression was significantly reduced during the early infusion compared to the pre-infusion values (P < 0.05). Isotonic saline did not influence the ES1 or ES2. In experiment 2, similar significant inhibitory changes were found in the ES2 on the painful side. In experiment 3, no significant effects on ES1 and ES2 were observed during painful infusion of hypertonic saline into the leg muscle. These results indicate that the effects of tonic jaw-muscle pain on ES2 can be distinguished from a generalized effect of muscle pain. Furthermore, there seems to be a differential and lateralized effect of jaw-muscle pain on the brain stem reflex circuits involved in the generation of ES1 and ES2 probably through a presynaptic mechanism.
Pain 1999 Sep
PMID:Modulation of exteroceptive suppression periods in human jaw-closing muscles by local and remote experimental muscle pain. 1048 76

Brain stem interneuronal excitability can be assessed by recording the recovery cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity. Abnormal endogenous pain control mechanisms due to disturbed brain stem interneuronal activity have been implicated in the pathogenesis of tension-type headaches. The blink reflex, exteroceptive suppression of temporalis muscle activity, and the recovery curve of both the R2 component of the blink reflex and the ES2 component of the exteroceptive suppression of the temporalis muscle activity were studied in 20 patients with migraine without aura, 32 patients with tension-type headache, and 20 normal controls. In our study, the blink reflex was elicited by stimulation of the supraorbital nerve; the exteroceptive suppression of the temporalis muscle activity was elicited by applying electrical shocks to the labial commissure, both on the lower and upper sides. The recovery cycle was established by delivering paired shocks at different interstimulus intervals. Comparisons were made between normal control subjects, patients with migraine without aura, and patients with tension-type headache. The latency of R1, R2, and R2', the amplitude and size of the R2 and R2' components of the blink reflex, the latency and duration of the ES1 and ES2 components, and the recovery curve of the ES2 component of the temporalis muscle activity did not differ between groups. However, the recovery curve of the R2 component of the blink reflex diminished in patients with tension-type headache compared with the other groups. Our findings indicate reduced excitability of the brain stem interneurons in patients with tension-type headache.
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PMID:Recovery cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity in migraine and tension-type headache. 1125 98

Brainstem-mediated antinociceptive inhibitory reflexes of the temporalis muscle were investigated in 82 patients (47 F, 35 M, mean age 28.3 years, SD 9.4) with acute posttraumatic headache (PH) following whiplash injury but without neurological deficits, bone injury of the cervical spine or a combined direct head trauma on average 5 days after the acceleration trauma. Latencies and durations of the early and late exteroceptive suppression (ES1 and ES2) and the interposed EMG burst (IE) of the EMG of the voluntarily contracted right temporalis muscle evoked by ipsilateral stimulation of the second and third branches of the trigeminal nerve were analyzed and compared to a cohort of 82 normal subjects (43 F, 39 M, mean age 27.7 years, SD 7.1). Highly significant reflex alterations were found in patients with PH with a shortening of ES2 duration with delayed onset and premature ending as the primary parameter of this study, a moderate prolongation of ES1 and IE duration and a delayed onset of IE. The latency of ES1 was not significantly changed. These findings indicate that acute PH in whiplash injury is accompanied by abnormal antinociceptive brainstem reflexes. We conclude that the abnormality of the trigeminal inhibitory temporalis reflex is based on a transient dysfunction of the brainstem-mediated reflex circuit mainly of the late polysynaptic pathways. The reflex abnormalities are considered as a neurophysiological correlate of the posttraumatic (cervico)-cephalic pain syndrome. They point to an altered central pain control in acute PH due to whiplash injury.
Pain 2001 Jun
PMID:Antinociceptive reflex alteration in acute posttraumatic headache following whiplash injury. 1137 4

Increased incidence of clinical pain complaints from patients with major depression, as well as increased experimental pain thresholds have been reported. The basis of this phenomenon remains unclear, as well as its relation to medication, clinical recovery, gender and lateralization of hemispheric function. We aimed to further elucidate heat pain perception in depression applying a testing battery including assessment (on both arms) of warmth perception, heat pain perception and heat pain tolerance, and the jaw opening reflex (duration of ES2 component) as a putative indicator of descending pain inhibition. The battery was applied to 20 patients and 20 age- and sex-matched controls. Patients were assessed: on admission (acutely depressed, off-medication), few days after admission (depressed, on medication), and after clinical recovery (mostly on medication), and controls at corresponding intervals. Significant elevated heat pain thresholds were found off and on medication in the acute stage (mainly in women) and after recovery on the right arm only. Elevated heat pain tolerance (on the right arm only) was seen in medicated patients in the acute and recovered stage. Significant prolongation of ES2 duration was only found in acutely depressed patients off medication. While confirming hypalgesia to heat pain in major depression, our findings demonstrate a close relation to gender and strong influence of lateralization after recovery. Altered pain processing at brain stem level might only partially be responsible for the observed finding.
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PMID:Influence of gender and hemispheric lateralization on heat pain perception in major depression. 1276 57

Stimulating afferent fibers of the trigeminal nerve usually causes two successive suppressions (ES1 and ES2) of the voluntary muscle activity of chewing muscles. The first phase of decreased voluntary activity is called the early exteroceptive suppression period (ES1); the second phase is called the late exteroceptive suppression period (ES2). Between these two suppression periods is a phase of increased muscle activity, the so-called facilitation period (FP). Usually, in healthy subjects this normal pattern of exteroceptive suppression can be elicited regularly. The reflex answer may occur at low non-painful stimulus intensities; however, typically it appears to be most pronounced with high-intensity stimuli. Because of the obvious relationship between stimulus intensity, pain perception and reflex answer, the reflex is regarded as an antinociceptive reaction. Chronic pain syndromes like chronic tension-type headache and migraine without aura cause changes within the normal ES recording pattern. Furthermore, some substances used in pain therapy such as serotoninagonists or antagonists, acetylsalicylic acid or naloxon may also alter the general appearance of the ES. In this review different parameters that influence the ES reflex answer are summarized. Above, the diagnostic value of the changes of the ES for pathophysiological procedures regarding pain perception and pain processing in certain pain diseases is discussed.
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PMID:[Exteroceptive suppression of activity of the temporal muscle in analysis of pain mechanisms]. 1279 57

The present study evaluated the reproducibility of the late exteroceptive suppression period (ES2) and of pain perception. The surface electro-myogram (EMG) was recorded from the left masseter muscle in 12 males and 12 females (22-31 year). Thirteen fixed stimulus intensities from 5 to 25 mA with 2.5 mA intervals were applied at random to the left mental area, and stimulus-response (S-R) curves were built for each subject. The first stimulation intensity at which the ES2 appeared was defined the reflex threshold, while the lowest stimulus intensity the subjects scored as painful, was called the pain threshold. Using the S-R curves, the other reflex parameters (appearance level, saturation level, slope from appearance to saturation, maximum duration of ES2, and maximum suppression degree) were also determined. Two measurement sessions were scheduled. Both the reflex and the pain sensation appeared at significantly lower stimulus intensity in females than males (P < 0.05). The reflex threshold, the reflex appearance and saturation level showed a significant decrease from the first to second session (P < 0.05), while the pain threshold was significantly higher during the second session (P < 0.01). By contrast, a good reproducibility was found for the maximum duration and suppression degree of ES2. Consequently, if S-R curves would be used to study the relation between the ES2 parameters and stimulus intensity in normal subjects for their applicability in clinical conditions, maximum duration and maximum suppression degree should be focused upon, in order to avoid session and gender effects as confounding factors.
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PMID:Reproducibility of the masseteric exteroceptive suppression period using stimulus-response curves. 1693 2


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