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Biomedical subjects

B Bromm

Publications and source records attributed to B Bromm.

At least 55 records · Page 3Linked to original sources
PubMed1991

Cerebral potentials evoked by painful, laser stimuli in patients with syringomyelia.

Brief cutaneous heat stimuli generated by a CO2 laser were used to elicit late somatosensory evoked cerebral potentials (SEPc) in 10 patients with syringomyelia. For comparison, early and late cerebral potentials in response to electrical nerve stimuli (SEPn) were recorded in the same session. In 8 patients with localized impairment of pain and temperature sensitivity we found complete absence of SEPc after stimulation of the affected area; in another patient with similar sensory deficits, the SEPc was grossly attenuated and delayed. In 1 patient with intact pain sensitivity but absent temperature sensitivity, a well defined SEPc could be recorded. Both early cortical SEPn and late SEPn in response to conventional nerve stimuli were normal in all patients and thus did not differentiate control and affected areas. These data indicate that alteration of SEPc correlates with altered pain sensitivity in patients with a circumscribed spinal lesion. SEPc may thus be used as a neurophysiological test in the assessment of hypalgesic dermatomes.

Brain↗
PubMed1991

Ultralate cerebral potentials in a patient with hereditary motor and sensory neuropathy type I indicate preserved C-fibre function.

Late and ultralate cerebral potentials in response to cutaneous heat (CO2 laser pulses) and electrical nerve stimuli were studied in a patient with hereditary motor and sensory neuropathy type I who showed severe impairment of myelinated nerve fibre function. Cerebral potentials in response to electrical stimuli were absent (tibial nerve) or small (median nerve). With the laser pulses applied to the foot only ultralate, but no late potentials were observed, indicating intact C-fibres, but disturbed A delta-fibres. Laser stimulation of the hand resulted in both late and ultralate components, indicating at least partly preserved A delta-fibre function. The results document the usefulness of laser stimuli in the assessment of small nerve fibre function.

Adult↗
PubMed1991

Laser-evoked cerebral potentials in the assessment of cutaneous pain sensitivity in normal subjects and patients.

Heat stimuli, applied to the skin by non-contact radiation pulses emitted by a CO2-laser, activate simultaneously both A-delta (mean conduction velocity 14 m/s) and C-fibres (0.8 m/s), which terminate in the most superficial skin layers. Correspondingly, brief heat stimuli elicit two pain sensations with mean reaction times of about 500 ms and 1400 ms. Similarly, two evoked potential waveforms were observed in the electroencephalogram: the late components N240/P370 and the ultralate components N1050/P1250. The shape of the two components was reproducible in independent samples of healthy volunteers. In patients with dissociated sensory loss, the laser evoked cerebral potentials are affected, depending on the kind of disturbed nerve and tracts. This is shown in patients with syringomyelia, encephalomyelitis disseminata, myelitis, Brown-Sequard syndrome, Wallenberg syndrome. In cases with hereditary motor and sensory neuropathy type I or with neurosyphilis, ultralate potentials are observed as correlates of delayed pain perception in the affected body areas. The laser evoked cerebral potentials reflected the clinical disorder of pain sensitivity in most cases, whereas somatosensory evoked potentials in response to conventional nerve stimuli failed in objectifying the diagnosis. As such, evoked cerebral potentials in response to laser heat stimuli applied to the hairy skin can be used for an overall examination of the functional integrity of peripheral small fibres, anterolateral tracts and thalamocortical projections.

Brain↗
PubMed1991

Central analgesic effects of acetylsalicylic acid in healthy men.

Acetylsalicylic acid (CAS 50-78-2) (1000 mg orally) was investigated in a non-inflammatory experimental pain model in healthy male volunteers, selected for maximal homogeneity. Phasic pain was induced by intracutaneously applied electrical pulses of constant current. The nociceptive responses measured were, the pain ratings, the cerebral potentials and the EEG delta power in response to the stimuli. In addition, spontaneous EEG, auditory evoked potentials and reaction times were evaluated to determine effects upon the vigilance system. The study was performed in a placebo-controlled, double-blind repeated measures design. Blood samples were taken to monitor the plasma concentrations of the active agents. Acetylsalicylic acid produced clear analgesic effects in all pain relevant target variables. The effects increased with post-medication time, becoming significantly different from placebo 90 min after medication (p less than 0.01). At this time point the pain ratings were reduced by 4%, the pain related cerebral potentials by 15%, and the stimulus induced delta power of the EEG by 20%. These findings suggest a central action of acetylsalicylic acid by attenuation of experimentally induced nociceptive activity. No influences could be observed upon auditory evoked potentials, spontaneous EEG and reaction times. In other words, acetylsalicylic acid did not change vigilance by unspecific alterations of the CNS. The plasma concentration of acetylsalicylic acid reached mean values of 2.5 +/- 2.4 micrograms/ml within 25 min after oral medication, which remained constant during the entire post-medication period of 105 min. In contrast, the concentration of the metabolite salicylic acid increased steadily reaching mean values of 32.0 +/- 16.8 micrograms/ml at the end of the investigated period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Modulation of pain-related somatosensory evoked potentials by general anesthesia.

The aim of the present study was to assess if late somatosensory evoked cerebral potentials (SEPs) in response to painful electrical stimuli are a sensitive indicator for analgesic treatment during general anesthesia. For this purpose, a pain model developed for the quantification of drug-induced analgesia in awake volunteers was used in 10 patients scheduled for elective abdominal hysterectomy. Before induction of anesthesia, stimuli were adjusted to two and three times the pain threshold for each individual. Late auditory evoked potentials (AEPs, 30 dB hearing level) and spontaneous electroencephalogram were also evaluated. After control recordings, anesthetic treatments were varied in the following sequences: (a) 0.8% (end-tidal) halothane with 70% nitrous oxide (HN); (b) 0.8% halothane in oxygen (H1); (c) same anesthetic condition as in H1, but the SEP and AEP stimulus intensities were increased to 15 times pain threshold and to 70 dB hearing level, respectively (H2); and (d) fentanyl (0.25 mg) was given with 0.8% halothane in oxygen with no further change in stimulus intensities (HF). In treatments HN and H1, blood pressure and heart rate increases to pain stimuli were abolished, and SEPs and AEPs were both suppressed. Increasing the somatosensory stimulus intensity (treatment H2) stimulated heart rate and arterial pressure responses and again elicited the SEPs. However, AEP components remained suppressed with increased auditory stimulus intensity. Addition of fentanyl (HF) suppressed SEP amplitudes and stimulus-induced hemodynamic responses. Our results suggest that late SEPs in response to painful stimuli change with different analgesic levels.

Adult↗
PubMed1989

[Comparison of the action of 2 effective analgesics. Experimental study: tramadol versus tilidine/naloxone].

In the present study involving healthy test subjects, tilidin/naloxone (Valoron N; VAL) proved to have an analgesic effect roughly twice as pronounced as that of tramadol (TRA). Moreover, the analgesic effect of VAL showed a significantly more rapid onset than did that of TRA. This finding reflects the difference in rate of action of the active substances. In accordance with these findings, VAL is thus the most powerful analgesic presently available on the German market on simple prescription.

Clinical Trials as Topic↗
PubMed1989

Pre-stimulus/post-stimulus relations in EEG spectra and their modulations by an opioid and an antidepressant.

Parametric spectral analysis of late cerebral potential components (later than 80 msec) evoked by painful somatosensory stimuli reveals a stimulus-induced increase of power in the low frequencies, delta and theta. This paper investigates the effect kinetics of the opioid meperidine (150 mg, p.o.) and the antidepressant imipramine (100 mg, p.o.) on spontaneous and evoked EEG activity in a placebo-controlled double-blind cross-over study with 20 healthy male subjects. Brief electrical stimuli (5 msec) were intracutaneously applied on the finger tip with randomized intensities above pain threshold and intervals between 10 and 20 sec. Spectra of short (500 msec) pre- and post-stimulus EEG epochs were evaluated using the maximum entropy method (model order 20). The main findings were: (1) The maximum effects of the 2 drugs upon spontaneous and evoked EEG activity were comparable: in the pre-stimulus (spontaneous) EEG both drugs increased the power in the low frequencies and decreased the power in the alpha range. In the post-stimulus (evoked) EEG the drugs decreased the power in all frequency bands. (2) Since in the low frequency range the drugs exhibited contrary effects upon spontaneous and evoked EEG activity, the pre-/post-stimulus relationship of the delta power was found to be the most sensitive measure for monitoring the cerebral bioavailability of the tested drugs. (3) The time courses of development of the effects of the two drugs were different: maximal effects of meperidine were obtained 85-105 min, and of imipramine 190-210 min after medication. The differences in the effect kinetics agreed with the different pharmacodynamics, with time constants for absorption and elimination of 40 min and 240 min for meperidine, and 240 min and 840 min for imipramine. (4) The most important difference between the 2 drugs was the different effect kinetic. Furthermore, in contrast to meperidine the effects of imipramine upon beta activity could not be separated from placebo, either in the spontaneous or in the evoked EEG activity.

Adult↗
PubMed1989

[Assessment of the effectiveness of analgesics in the pain laboratory].

In 1987 the Fifth World Congress on Pain was held in Hamburg with about 2,500 participants, for the first time in Germany after the previous congresses in Florence, Montreal, Edinburgh and Seattle. --In the following lines, Professor Bromm, one of the organisers of the congress, gives a brief insight into modern methods to measure the efficacy of analgesics.

Analgesics↗
PubMed1989

[Analysis of the effect of quisqualate, N-methyl-D- aspartate and several blockers of amino acid receptors on synaptic transmission in the ampullae of Lorenzini].

Effects of bath-application of quisqualate (Q), N-methyl-D-aspartate (NMDA) and antagonists of NMDA-receptors: D-amino-adipate (AA), 2-amino-4-phosphonobutyrate (APB), 2-amino-5-phosphonovalerate (APV) and Mg2+ as well as acidic amino acid antagonist: D-glutamylglycine (DGG) on the synapse between the electroreceptor cells and afferent fibres were studied in the ampullae of Lorenzini. Q (threshold concentration 10(-8) M) and NMDA (threshold concentration 10(-5) M) strongly excited afferent fibres. Neither AA nor APB influenced the resting and evoked activities. APV blocked the synaptic transmission. Mg2+ (30-50 mM) blocked the responses to NMDA, while Q-induced responses were not affected, APV preferentially blocked NMDA-induced responses and in lesser degree--L-aspartate (L-ASP)-induced responses. DGG blocked the synaptic transmission. It is supposed that the synaptic receptor could represent a homogeneous receptor with different binding sites to the known agonists.

2-Amino-5-phosphonovalerate↗
PubMed1988

Late somatosensory evoked cerebral potentials in response to cutaneous heat stimuli.

Late components of cerebral potentials evoked by brief heat pulses applied to various skin sites were used to monitor the afferent pathways of pain and temperature sensitivity. Radiation at 10.6 micron wave length generated by a CO2 laser stimulator predominantly activates superficial cutaneous A delta and C nociceptors and elicits late and ultralate cerebral potentials. This paper deals with the investigation of the component structure and topography of the A delta fibre mediated late potentials, which were compared with the corresponding late potentials in response to standard electrical nerve stimuli. In the upper limb both stimulus types evoked a large positive potential (nerve: 260 msec, skin: 390 msec latency), preceded by a negativity (nerve: 140 msec, skin: 250 msec). Whereas these components were always maximal at the vertex, an earlier negativity appeared over the somatosensory projection area (nerve: 70 msec, skin: 170 msec). After stimulation of the lower limb all latencies were delayed by 20-30 msec. As a rule, the heat-evoked potentials appeared about 100 msec later than the corresponding potentials after electrical nerve stimulation. Similarities in interpeak latencies and scalp topography indicated similar cerebral processing.

Adult↗
PubMed1988

Ultralate cerebral potentials as correlates of delayed pain perception: observation in a case of neurosyphilis.

Evoked cerebral potentials were investigated in a patient with neurosyphilis, who showed the symptoms of delayed pain perception in the lower limbs: a pinprick to the legs was perceived with a latency of more than one second. After stimulation with CO2 laser radiant heat pulses, evoked cerebral potentials of upper limbs were observed in a latency range comparable to those of healthy subjects, with a negative peak at 250 ms and a positive peak at 370 ms. In contrast, after application of laser stimuli to body sites with delayed pain perception, latency of the evoked potentials drastically increased with a vertex negativity at 1300 ms and a positivity at 1420 ms. Evoked potential measurements with conventional electrical stimuli did not show any difference between affected and unaffected body sites, that is, stimulation of the affected body sites did not produce pathological potentials.

Afferent Pathways↗
PubMed1987

Human cerebral potentials evoked by CO2 laser stimuli causing pain.

Brief radiant heat pulses, generated by a CO2 laser, were used to activate slowly conducting afferents in the hairy skin in man. In order to isolate C-fibre responses a preferential A-fibre block was applied by pressure to the radial nerve at the wrist. Stimulus estimation and evoked cerebral potentials (EP), as well as reaction times, motor and sudomotor activity were recorded in response to each stimulus. With intact nerve, the single supra-threshold stimulus induced a double pain sensation: A first sharp and stinging component (mean reaction time 480 ms) was followed by a second burning component lasting for seconds (mean reaction time 1350 ms). Under A-fibre block only one sensation remained with characteristics and latencies of second pain. The heat pulse evoked potential consisted of a late vertex negativity at 240 ms (N240) followed by a prominent late positive peak at 370 ms (P370). Later activity was not reliably present. Under A-fibre block this late EP was replaced by an ultralate EP beyond 1000 ms, which in the conventional average looked like a slow halfwave of 800 ms duration. This potential was distinct from eye movements, skin potentials or muscle artefacts. With cross-correlation methods waveforms similar to the N240/P370 were detected in the latency range from 900 to 1500 ms during A-fibre block, indicating a much greater latency jitter of the ultralate EP. Latency corrected averaging with a modified Woody filter yielded a grand mean ultralate EP (N1050/P1250), the shape of which was surprisingly similar to the late EP (N240/P370). The similarity of these components indicates that both EPs may be secondary responses to afferent input into neural centers, onto which myelinated and unmyelinated fibres converge. Such convergence may also explain through the known mechanisms of short term habituation and selective attention, why ultralate EPs are not reliably present without peripheral nerve block.

Adult↗
PubMed1987

Pain related cerebral potentials: late and ultralate components.

Brief CO2 laser radiant heat pulses activate both A delta- and C-fibres. In the evoked potential (EP) late and ultralate components can be seen as correlates of first and second pain. Usually the ultralate EP appears to be suppressed. It could be uncovered by a preferential A-fibre block, and in two neurological patients with tabes dorsalis and with a polyneuropathy involving myelinated fibre loss. Due to a strong latency jittering the shape of the ultralate component is distorted in the conventional average. Latency corrected averaging, adaptive filters or parametric spectral estimators are needed to analyze these EP components. As a result the filtered ultralate waveforms look very similar to the late EP components. Clinical application of CO2 laser EPs promises to nonivasively assess A delta- and C-fibre function.

Action Potentials↗
PubMed1987

The analgesic efficacy of flupirtine in comparison to pentazocine and placebo assessed by EEG and subjective pain ratings.

In a placebo-controlled double-blind study the analgesic efficacy of the non-narcotic analgesic flupirtine (80 mg i.v.) was evaluated in comparison with the opioid pentazocine (30 mg i.v.). The variables investigated were the subjects' pain ratings (E), the somatosensory evoked cerebral potentials (SEP), the auditory evoked potentials (AEP) and the power spectral density of the ongoing EEG (PSD). One stimulus block before (PRE) and one stimulus block after (POST) medication were applied. In one stimulus block 80 intracutaneous electrical stimuli of two- and three-fold pain threshold amperage were given in randomized order of intensity and inter-stimulus intervals. Both treatments reduced the subjects' pain ratings significantly, while the placebo values were constant. These effects on pain ratings were in parallel with the SEP changes. The peak-to-peak amplitudes of the late components were significantly diminished by both drugs. Placebo had no effect on this variable. The AEPs remained considerably constant after all three treatments indicating specific drug effect on the pain-related somatosensory pathways. Flupirtine showed effects similar to those of pentazocine in terms of pain relief. The changes in ongoing EEG activity, however, were of a different kind. Pentazocine changed the EEG in an opiate-like manner, while flupirtine increased relative power in the theta and beta range.

Aminopyridines↗
PubMed1987

Assessment of analgesia by evoked cerebral potential measurements in humans.

This paper gives a brief account of new methods for the evaluation of pain and analgesia in healthy male volunteers by use of evoked cerebral potentials. In pain research, the so-called late components with latencies between 100 and 400 ms are usually used, but these potentials are non-specific, depending on a variety of factors e.g. on the activity of the ongoing electroencephalogram (EEG) on the subject's arousal/attention mechanisms, on the novelty of the stimulus and on its painfulness. Therefore, if evoked cerebral potentials in response to phasic pain stimuli are to be evaluated quantitatively, constant experimental conditions are essential, including subject selection to obtain as uniform a sample of volunteers as possible. Latency variation in evoked potential components in single studies makes signal averaging methods rather inaccurate to predict the effects of weak analgesics upon cerebral potentials in relation to time. Therefore single trial studies have been performed using transformation of post-stimulus EEG activity in terms of frequency. Because of the short duration of the evoked potentials, various parametric spectral estimators have been investigated for their advantages in EEG analysis. Frequency transformation of stimulus-induced cerebral activity by means of the maximum entropy method gives an enormous increase in the power in the 2-4 Hz frequency band with a very constantly located maximum. Examples are given showing that in this way it might be possible to monitor the time course of efficacy of even so-called weak analgesics.

Brain↗