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

A series of eight patients in a persistent vegetative state (PVS) were subjected to chronic deep brain stimulation (DBS) for the purpose of promoting recovery from the PVS. The characteristics of the brain activity in these patients were evaluated from the late positive component of the cerebral evoked potential in response to painful stimuli (pain-related P250). While any neurological scoring system for the comatose state includes evaluations of motor reactions to painful stimuli, the pain-related P250 is unique in terms of its ability to assess the cortical responsiveness to painful stimuli directly and quantitatively without involving functions of the motor system. It was found that the pain-related P250 was more or less depressed in patients in a PVS. It was repeatedly demonstrated in four patients, however, that the pain-related P250 could be transiently increased by preceding stimulation of the mesencephalic reticular formation. Furthermore, a persistent increase in the pain-related P250 was produced in these four patients following chronic DBS of the mesencephalic reticular formation or nonspecific thalamic nuclei for more than 6 months, and this was correlated with the clinical improvements. These results imply that responsiveness at the cortical level to pain is depressed in the PVS. It also appears that some fraction of the depression may, however, be functionally produced and potentially reversible.
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PMID:Characterization and modification of brain activity with deep brain stimulation in patients in a persistent vegetative state: pain-related late positive component of cerebral evoked potential. 170 25

Human evoked potentials (EP) to paired somatosensory pain stimuli were recorded from the vertex. Amplitude of the N150 and P250 components of the second EP decreased within 600-1000 ms interstimulus interval. The depression occurred was more intensive with an increase of the first (conditioning) stimulus strength. As a rule, depression of N150 component was more pronounced. Selective averaging of EPs indicated that, when the stimulus intensity was stable, variations in the amplitudes of identical components in response to the first and second stimuli were not usually negatively correlated; positive correlation was frequently found. This can be regarded as a proof that there is no direct relation between the inhibitory after-processes in the cellular generators of the studied EP components and the degree of their previous activation. Such variations can reflect the sequence of periods of an increase and a decrease in the generator activity under conditions of stable stimulus intensity.
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PMID:[Effect of the intensity of stimulation on the variability and interactions of various late components of the somatosensory evoked potentials in humans]. 208 82

The pain components of somatosensory evoked potentials (SEPs) induced by nervi tibialis posterior stimulation were studied by blocking bloodstream of leg in 10 normal adults. The SEPs following the painful stimuli (0.1 msec square wave pulse) of the right ankle were recorded from the parietal median (C'Z) and the reference electrode at earlobe. The pressure of 80 mmHg above the arterial pressure was given to the right calf by sphygmomanometer. The result showed that the P250-N350 components (latency 244.2 +/- 10.1 msec and 344.2 +/- 14.9 msec) of the SEPs persisted and the others disappeared when tactile sensation disappeared but pain existed. It suggested the P250-N350 were the pain potentials of nervi tibialis posterior SEPs.
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PMID:[The components of somatosensory evoked potentials P250-N350 induced by nervi tibialis posterior stimulation]. 775 Jan 80

The effect of intravenous midazolam on the somatosensory evoked potentials (SEP's) elicited from median nerve stimulation was investigated in a study on 20 volunteers. SEP's were recorded from contralateral scalp before and at 5, 30, and 60 min after drug administration. Relative amplitudes of the early components (N18-N20) were essentially stable, while relative amplitudes of the late components (N50-P90, P90-N160, N160-P250 and P250-N380) were reduced significantly after midazolam administration and had not returned to baseline 60 min after administration. Given the correlation between late SEP amplitude and subjective reports of experimental pain, the data support the possibility that administration of midazolam in conscious sedation doses may have some effect on pain in addition to its better documented sedative and amnesic properties.
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PMID:Midazolam and somatosensory evoked potentials. 843 10

The present study investigated the processing of painful electrical stimuli in patients with unilateral frontal or parietal lobe damage and matched control subjects. Patients with frontal lesions showed increased pain thresholds when the stimuli were administered contralateral to the lesion. While the peak-to-peak amplitudes of the N150/P250 components of the somatosensory potentials increased linearly with stimulus intensity in the control subjects, the responses in the frontal group did not change significantly between stimulation at pain and tolerance threshold. There was no evidence for altered pain processing in patients with parietal lobe lesions. The findings of the present study support the hypothesis of an involvement of the frontal cortex in pain perception in humans.
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PMID:Pain-related cerebral potentials in patients with frontal or parietal lobe lesions. 855 79

Pain assessment in human volunteers is difficult, and it often requires a large number of subjects to show analgesic efficacy with statistical significance. Electrical tooth pulp stimulation elicits a painful sensation and produces an electroencephalographic (EEG) signal that can be recorded from the scalp when precisely controlled dental stimuli are delivered. These somatosensory evoked potentials (EP) consist of a series of peaks or waves each characterized by their polarity, latency, and amplitude. They are obtained by processing the EEG signals that occur after tooth pulp stimulation. There is good correlation between subjective pain reports and evoked potential amplitudes (N150-P250 component). Thus, EP may provide a useful model for the assessment of analgesic activity in human volunteers. We describe an improved method for producing and recording tooth pulp evoked potentials in six healthy subjects. Only 16 EEG epochs were necessary to get a reproducible EP response from the participants. The approach was applied to study the efficacy of codeine (60 mg administered orally); a decrease in the evoked potential amplitudes after codeine administration was observed. The data were consistent with results from visual analog pain ratings given by the subjects.
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PMID:Pharmacodynamic evaluation of codeine using tooth pulp evoked potentials. 901 69

The differential effects of painful stimulation of skin vs. muscle on the cerebral electrophysiology have been poorly described. This study examined the somatosensory evoked potentials (SEPs) and the associated dipole models of non-painful and graded painful electrical stimulation applied to the skin and muscle in 20 healthy subjects. With the psychophysical stimulus-response functions determined, the skin stimulation showed a steeper slope than muscle stimulation. For both types of stimulation, the SEPs indicated a similar temporo-spatial activation sequence: F4/N90-P4/P95, Fc2/N135, Cz/P250, Cz/P300, and Cz/N460. The SEP amplitudes increased significantly with the stimulus intensities in these components. The peak SEP latencies of skin stimulation were in general shorter than that of muscle stimulation. The SEP amplitudes to skin stimulation were significantly larger than those caused by muscle stimulation at every stimulus intensity level, except the early mid-latency component. In this case, muscle stimulation caused higher amplitudes over the contralateral parietal-frontal sites. For both types of stimulation, the topographic maps were quite similar. Equivalent dipole modeling revealed identical site parameters (<1.0 cm) between skin and muscle stimulation. However, the electrical skin stimulation did not correlate with the pain intensity. Pain intensity, in contrast, was uniquely associated with the Cz/P250 amplitudes for the muscle stimulation. It is concluded that non-nociceptive and nociceptive electrical stimuli applied to skin and muscle are processed in the common cerebral areas, but exhibit differential SEP effects.
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PMID:Dynamic brain topography of somatosensory evoked potentials and equivalent dipoles in response to graded painful skin and muscle stimulation. 1107 93

Temporal summation is a potent central somatosensory mechanism and may be a major mechanism involved in e.g. neuropathic pain. This study assessed the long-latency somatosensory evoked potentials (SEPs) in response to trains of repeated painful electrical stimulation of human skin and muscle in order to investigate the cerebral representation of temporal summation. Forty series of stimuli were delivered at stimulus intensities corresponding to moderate pain levels in 20 young men. Each series consisted of a five-burst-pulses (1 ms) train delivered at 2 Hz, known to activate temporal summation, i.e. increased pain intensity during the series of stimuli. Grand mean averaged waveforms (31 ch. EEG) were obtained in response to the skin and muscle stimulation. In the "train" SEPs, the wave morphology was characterized by four peak components after the first stimulus (100 to 450 ms) and by three components after the fifth stimulus (2100-2145 ms). The latency was significantly prolonged for muscle stimulation only. The 3D topographic maps at the peak activation time (100, 140, 250, and 450 ms) showed clear reduction in the amplitudes and their spatial extent (P4/P100-Fc2/N100, POz/P140-Fc2/N140, Cz/P250, Cz/N460) betweenthe first and the fifth stimulus. The current source density (CSD) topology exhibited markedly differential patterns changing from the first to the fifth stimulus. For the skin stimulation, the fifth stimulus was associated with a distinct emergence of the frontal negativity source at Fc2 right frontal cortex. This was consistent across the 100,140, 250, and 450 peak components but was not even visible in the first stimulus. In the muscle, the fifth stimulus was associated with a marked reduction of the frontal positivity at contralateral F4 site in the early stages at 100 and 140 ms, and with a total disappearance of positive source at Cz. In summary, this study demonstrated a clear temporal summation of psychophysical ratings, reduction of the peak amplitudes in the last of the first stimuli, dissociation from simple amplitude increase of the cerebral responses to pain, and a concurrent transformation of the CSD patterns. This change in "rapid cortical dynamics" of short-term plasticity could be an important mechanism for wind-up and pain processing in the brain.
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PMID:Brain dynamics of scalp evoked potentials and current source densities to repetitive (5-pulse train) painful stimulation of skin and muscle: central correlate of temporal summation. 1107 94

The main goal was to evaluate the motor and somatosensory systems by recording evoked motor responses (EMRs) during transcranial magnetic stimulation (TMS) and somatosensory evoked potentials (SEPs) in patients with neurogenic pain syndromes before and after implantation of the systems for chronic antipain epidural stimulation. Fifteen patients with neurogenic pain syndromes and a control group of 15 apparently healthy examinees were examined. The patients were found to have a significant reduction in the motor thresholds of EMRs during TMS and an increase in the amplitude of EMRs after implantations of the systems. There were no significant changes in the amplitude-time characteristics of short SEPs as compared to the healthy examinees and after implantation of the systems. Analysis of the amplitude-time characteristics of long SEPs in these patients revealed a significant increase in the amplitude of the component P250 as compared to the normal values and its decrease after implantation of the systems.
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PMID:[Motor responses in transcranial magnetic stimulation and somatosensory evoked potentials in patients with pain syndromes]. 1187 12

Twenty cases of a persistent vegetative state (PVS) caused by various kinds of brain damage were neurologically and electrophysiologically evaluated at 3 months after persistence of the PVS, and were treated by deep brain stimulation (DBS) therapy. The stimulation sites were the mesencephalic reticular formation (2 cases) and CM-pf complex (18 cases). Seven of the patients emerged from the PVS, and became able to obey verbal commands. However, they remained in a bedridden state. These 7 cases revealed a desynchronization or slight desynchronization pattern on continuous EEG frequency analysis. The Vth wave of ABR and N20 of SEP could be recorded even with a prolonged latency, and the pain-related P250 was recorded with an amplitude of over 7 microV. We conclude that chronic DBS therapy may be useful for allowing the patient to emerge from a PVS, if the candidates are selected according to the neurophysiological criteria. In view of the severely disabled state of the patients who emerged from the PVS, a special rehabilitation program which includes neurostimulation therapy may be necessary for treatment of the PVS.
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PMID:Deep brain stimulation therapy for a persistent vegetative state. 1197 94


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