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Quantitative evaluation of EMG pain
Sl16 high-clinical pain group vs. the low-clinical pain group, and suggests relationships between brain psychophysiology and patterns of pain responsiveness.
decrease in MSC (especially in frequencies 4 - 8 Hz) and increase in NVP, PAG and M R F (with the shift to frequencies of 5-10 Hz). Evoked potentials (EP) became flat in M R F and NVP after mecamylamine. Administration of atropine resulted in more negative EPs in every tested structure.
P12.03 Q U A N T I T A T I V E EVALUATION OF E M G PAIN. S. Khoshbin, M. Hallett and R. Lunbeck (Bethesda, MD, USA) The pain of E M G is not only unpleasant for the patient, but frequently limits the amount that can be accomplished in a study. We sought to identify factors which would predict the amount of pain that a patient would experience. 82 patients sent to the E M G Laboratory as part of an evaluation of low back pain were given questionnaires before and after the test. Features explored included sex, age, race, education, pre-medication with analgesics, trait-anxiety, state-anxiety, duration of the EMG study, patient's assessment of his or her own pain and whether the patient was told that the test was painful. EMG was performed with concentric needle electrodes in the muscles of both lower extremities. The features predictive of E M G pain were patient's assessment ofhis own pain (by the McGill pain questionnaire), traitanxiety (by Speilberger inventory) and female sex. By stepwise linear regression they accounted for 34% of the variance of the E M G pain. Three patients terminated the test prematurely and all had high E M G pain. Results of the study also demonstrated that patients coming for E M G testing have high levels of state-anxiety and this can be decreased by information about the nature of the test.
P12.04 A U T O M A T I C ANALYSIS O F T H E BRAIN BIOELECTRICAL ACTIVITY IN T H E S T U D Y O F T H E R O L E O F P E R I A Q U E D U C T A L GRAY CHOLINERG1C STRUCT U R E S IN T H E P E R C E P T I O N OF A C U T E PAIN.
Pi2.05 S O M A T O S E N S O R Y AND A U D I T O R Y VERTEX P O T E N T I A L S ARE DIFFERENTIALLY INFLUENCED BY CENTRALLY ACTING DRUGS. B. Bromm, W. Meier and E. Scharein (Hamburg, W. Germany) Cerebral potentials (Cz-lead) were evoked by painful intracutaneous electrical shocks (SSEP) followed 2.5 sec later by an acoustic stimulus (AEP) of comparable intensity. 80 stimuli per modality were given as stimulus blocks lasting 20 min. One preand 6 post-treatment stimulus-blocks were applied in each session. SSEPs and AEPs were averaged per stimulus block to evaluate the peak-to-peak amplitudes of late components. The opioid meperidine (150 rag), the antidepressant imipramine (100 rag), the weak analgesic fluradoline (450 mg) and placebo were administered orally in a double blind cross-over study with 20 healthy male subjects. Placebo reduced amplitudes of SSEP (9%) and AEP (7%) in stimulus block 1 after treatment. Then the AEP amplitudes remained constant in all following stimulus blocks. This was similar for every treatment. In contrast, a drug specific and time dependent modulation of the SSEP amplitudes was observed: under meperidine the SSEP amplitudes were diminished by 43% within the first two stimulus blocks. The antidepressant imipramine caused a similar decrease of SSEP amplitudes, but with a delay of about 1 hour. The different time courses in amplitude reductions correlated with reductions of pain ratings. Thu's the centrally acting drugs influence differentially the AEPs and the SSEPs, only the tatter reflecting analgesia.
M. Kowalczyk, S. Rump and A. Wojewoda
(Warsaw, Poland) Experiments were performed on conscious rabbits with chronically implanted electrodes into the motor-sensory cortex (MSC), thalamic ventro-posterior nuclei (NVP), midbrain reticular formation (MRF) and periaqueductal gray (PAG) and cannulas implanted into PAG. Painful stimulation was carried out by means of electric pulses applied to the front paw (30 V, 50 Hz, 3 msec for 5 sec. Cholinergic structures in P A G were blocked by local administration of atropine (M-structures) or mecamylamine (N-structures) (20 1M, 3 ~1). Bioelectrical activity was automatically analysed by means of power spectrum analysis using the Fast Fourier Transform. It was found that mecamylamine caused significant decrease in power spectra in MSC (especially in frequencies 2 4, 9 and 21-11 Hz) and increase in M R F (with the shift to frequencies of 5 - 1 2 Hz) and atropine -
P12.06 CIRCADIAN C H A N G E S OF NOCICEPTIVE FLEXION REFLEX T H R E S H O L D IN MAN. G. Sandrini, Nappi
E. Alfonsi, F. Facchinetti. G. Micieli and G.
(Pavia, Italy) There is disagreement in the literature about 24 hour changes of subjective pain threshold in man. Some authors found no variations, while others described higher values in the afternoon and evening than in the morning. In this study circadian changes of nociceptive flexion reflex in 8 healthy male volunteers (23-34 yrs) were examined measuring RIII threshold every 6 hours from noon on. In four subjects plasma B-endorphin levels were studied simultaneously, to evaluate a possi-
decrease in MSC (especially in frequencies 4 - 8 Hz) and increase in NVP, PAG and M R F (with the shift to frequencies of 5-10 Hz). Evoked potentials (EP) became flat in M R F and NVP after mecamylamine. Administration of atropine resulted in more negative EPs in every tested structure.
P12.03 Q U A N T I T A T I V E EVALUATION OF E M G PAIN. S. Khoshbin, M. Hallett and R. Lunbeck (Bethesda, MD, USA) The pain of E M G is not only unpleasant for the patient, but frequently limits the amount that can be accomplished in a study. We sought to identify factors which would predict the amount of pain that a patient would experience. 82 patients sent to the E M G Laboratory as part of an evaluation of low back pain were given questionnaires before and after the test. Features explored included sex, age, race, education, pre-medication with analgesics, trait-anxiety, state-anxiety, duration of the EMG study, patient's assessment of his or her own pain and whether the patient was told that the test was painful. EMG was performed with concentric needle electrodes in the muscles of both lower extremities. The features predictive of E M G pain were patient's assessment ofhis own pain (by the McGill pain questionnaire), traitanxiety (by Speilberger inventory) and female sex. By stepwise linear regression they accounted for 34% of the variance of the E M G pain. Three patients terminated the test prematurely and all had high E M G pain. Results of the study also demonstrated that patients coming for E M G testing have high levels of state-anxiety and this can be decreased by information about the nature of the test.
P12.04 A U T O M A T I C ANALYSIS O F T H E BRAIN BIOELECTRICAL ACTIVITY IN T H E S T U D Y O F T H E R O L E O F P E R I A Q U E D U C T A L GRAY CHOLINERG1C STRUCT U R E S IN T H E P E R C E P T I O N OF A C U T E PAIN.
Pi2.05 S O M A T O S E N S O R Y AND A U D I T O R Y VERTEX P O T E N T I A L S ARE DIFFERENTIALLY INFLUENCED BY CENTRALLY ACTING DRUGS. B. Bromm, W. Meier and E. Scharein (Hamburg, W. Germany) Cerebral potentials (Cz-lead) were evoked by painful intracutaneous electrical shocks (SSEP) followed 2.5 sec later by an acoustic stimulus (AEP) of comparable intensity. 80 stimuli per modality were given as stimulus blocks lasting 20 min. One preand 6 post-treatment stimulus-blocks were applied in each session. SSEPs and AEPs were averaged per stimulus block to evaluate the peak-to-peak amplitudes of late components. The opioid meperidine (150 rag), the antidepressant imipramine (100 rag), the weak analgesic fluradoline (450 mg) and placebo were administered orally in a double blind cross-over study with 20 healthy male subjects. Placebo reduced amplitudes of SSEP (9%) and AEP (7%) in stimulus block 1 after treatment. Then the AEP amplitudes remained constant in all following stimulus blocks. This was similar for every treatment. In contrast, a drug specific and time dependent modulation of the SSEP amplitudes was observed: under meperidine the SSEP amplitudes were diminished by 43% within the first two stimulus blocks. The antidepressant imipramine caused a similar decrease of SSEP amplitudes, but with a delay of about 1 hour. The different time courses in amplitude reductions correlated with reductions of pain ratings. Thu's the centrally acting drugs influence differentially the AEPs and the SSEPs, only the tatter reflecting analgesia.
M. Kowalczyk, S. Rump and A. Wojewoda
(Warsaw, Poland) Experiments were performed on conscious rabbits with chronically implanted electrodes into the motor-sensory cortex (MSC), thalamic ventro-posterior nuclei (NVP), midbrain reticular formation (MRF) and periaqueductal gray (PAG) and cannulas implanted into PAG. Painful stimulation was carried out by means of electric pulses applied to the front paw (30 V, 50 Hz, 3 msec for 5 sec. Cholinergic structures in P A G were blocked by local administration of atropine (M-structures) or mecamylamine (N-structures) (20 1M, 3 ~1). Bioelectrical activity was automatically analysed by means of power spectrum analysis using the Fast Fourier Transform. It was found that mecamylamine caused significant decrease in power spectra in MSC (especially in frequencies 2 4, 9 and 21-11 Hz) and increase in M R F (with the shift to frequencies of 5 - 1 2 Hz) and atropine -
P12.06 CIRCADIAN C H A N G E S OF NOCICEPTIVE FLEXION REFLEX T H R E S H O L D IN MAN. G. Sandrini, Nappi
E. Alfonsi, F. Facchinetti. G. Micieli and G.
(Pavia, Italy) There is disagreement in the literature about 24 hour changes of subjective pain threshold in man. Some authors found no variations, while others described higher values in the afternoon and evening than in the morning. In this study circadian changes of nociceptive flexion reflex in 8 healthy male volunteers (23-34 yrs) were examined measuring RIII threshold every 6 hours from noon on. In four subjects plasma B-endorphin levels were studied simultaneously, to evaluate a possi-