Biomedical subjects

B Bromm

Publications and source records attributed to B Bromm.

At least 37 records · Page 2Linked to original sources

PubMed1996

[Differentiation of pain-related and morphine related impairment of cognitive performance and mood in bone marrow transplantation patients].

AIMS: Severe pain of mucositis induced by cytostatic conditioning therapy in bone marrow transplantation (BMT) patients generally requires continuous parenteral opioid treatment. Cognitive and psychological disturbances are frequent complications subsequent to BMT and may result from cerebral opioid side effects. The aim of the study was to evaluate the efficiency of continuous morphine in mucositis pain and the side-effects in BMT patients. Particular emphasis was placed on the question of whether reaction times, which are usually measured to estimate opioid effects upon vigilance, are influenced by pain-induced cognitive impairments in pain patients. METHODS: While in hospital, 10 BMT patients were examined daily with the aid of a mucositis scale, subjective visual analog scales (VAS) for pain and mood parameters, a German version of the McGill pain questionnaire (MPQ), and a mental performance task battery, and the morphine given was documented. Mental performance tests were simple auditory reaction time and choice reaction time. Seven patients also performed a Sternberg memory search test in which they had to use 'yes' and 'no' response keys to match visually presented test letters to a previously memorized set of letters. Practice and baseline data were collected within the first week before BMT. RESULTS: The intensity and duration of mucositis differed from patient to patient, resulting in different pain intensities and MPQ scores. Prolongation of the choice reaction time averaged over the period of mucositis treatment correlated significantly with residual pain intensity (Spearman r(s) = 0.88, p < 0.01) but not with morphine dose (r(s) = 0.35, p = 0.33). For the Sternberg memory search test greater correlation coefficients resulted between reaction time and morphine dose (r(s) = 0.86, p = 0.014) than between reaction time and residual pain intensity (r(s) = 0.61, p = 0.15). In turn, pain intensity, unlike morphine dose, was significantly correlated with high scores in the mood parameters for depression, passivity, and tiredness. CONCLUSIONS: It is concluded that both pain and morphine can impair cognitive performance, but that these mental stressors seem to differ according to qualitative criteria. Whereas pain might slow reaction time by distracting a patient's attention, particularly in low mental demand tasks, morphine could interfere with more specific cognitive processes, such as short-term memory operations, that are required in more complex tasks.

English Abstract↗

PubMed1996

Correlations between histamine-induced wheal, flare and itch.

Correlations between the skin reactions wheal and flare and the subjectively reported degree of itch were investigated in response to 1% histamine, intradermally applied by standardized skin prick and by iontophoresis. Experiments were performed with 15 male volunteers using a threefold repeated measures design (skin prick, and iontophoresis with 0.13 mA for 10 s and with 2.0 mA for 10 s). Skin reactions (perpendicular diameters) were determined at the time of their maximum (10 min). Itch was rated on a computerized visual analogue scale which was anchored upon the individual scratch threshold. Most effective in producing itch was the skin prick which caused strong sensations markedly above the scratch threshold during the entire period of measurement (30 min), whereas iontophoresis induced only transient itch sensations. On the other hand, the largest wheals were generated by iontophoresis of both intensities (mean 10 or 14 mm vs 6 mm with skin prick). The higher current induced higher itch, wheal and flare responses, but after eliminating this effect of stimulus intensity, no correlations were found. In contrast, skin prick-induced flare reactions varied with the degree of itch above the scratch threshold (r = 0.56; P < 0.01). Repeated measurements showed a higher stability for the itch reaction with skin prick compared with iontophoresis. It is hypothesized that in iontophoresis the brief (10-s) histamine bolus passed the most superficial pruritoceptive C fibres too quickly to induce long-lasting itch sensations, whereas the skin prick caused a deposit at the dermal-epidermal junction releasing histamine during the entire time of measurement. Consequently, both the C fibre-mediated itch and the axon reflex flare were more pronounced with the skin prick, and the wheal resulting from a permeability increase in the postcapillary venule walls was an independent phenomenon.

Adult↗

PubMed1996

Middle and long latency somatosensory evoked potentials after painful laser stimulation in patients with fibromyalgia syndrome.

Ten female patients with fibromyalgia syndrome (FS) were investigated with laser evoked potentials (LEPs) after hand stimulations and compared with 10 female pain-free and age-matched control patients. FS patients exhibited significantly lower heat pain thresholds than controls (P < 0.05) and had higher amplitudes of LEP components N170 (P < 0.01) and P390 (P < 0.05) in response to intensities of 20 W (beam diameter 5 mm, duration 20 msec, wavelength 10.6 microns). N170 additionally appeared with a broader distribution over bilateral central, vertex and fronto-central leads which contrasted to the control group and studies in healthy subjects where N170 was much more restricted to central and midtemporal positions contralateral to the stimulated hand. Auditory stimuli interspersed between laser impulses that served to announce subjects to rate the perceived pain elicited auditory evoked potentials that were not different between groups indicating no differences of general vigilance level to account for observed LEP effects. P390 amplitude enhancement might indicate greater attention and cognitive processing of nociceptive stimuli in FS subjects. Effects upon N170 rather point to exogenous factors like peripheral and spinal sensitization or reduced cortical or subcortical inhibition of nociception.

Adult↗

PubMed1996

Analgesic efficacy of low-dose ketamine. Somatosensory-evoked responses in relation to subjective pain ratings.

BACKGROUND: Low-dose ketamine has been shown to exert analgesic effects. Whether ketamine-induced pain relief may be quantitated by somatosensory evoked cerebral potentials has not been established. METHODS: Thirty healthy volunteers were assigned randomly to one of three groups. Subjects of group 1 (n = 10, control) were given saline as placebo. In groups 2 (n = 10) and 3 (n = 10), intravenous ketamine (0.25 mg. kg-1 and 0.50 mg. kg-1, respectively) was administered. The following variables were recorded at baseline and for 50 min after drug administration: electroencephalographic (EEG) data, somatosensory-evoked late cortical responses (SEP) elicited by intracutaneous stimulation of the fingertip (2-3 fold pain threshold), heart rate, mean arterial blood pressure, and end-tidal PETCO2 via a tight-fitting mask. Electroencephalographic spectral power in selected frequency bands and frequency percentiles were calculated from the spontaneous EEG segment preceding each somatosensory stimulus. Somatosensory-evoked late cortical response parameters were calculated from the respective poststimulus EEG segments. After recording of each EEG response, subjects were asked to rate the individual pain sensation. RESULTS: In group 1, all variables did not change over time. Ketamine administration resulted in dose-dependent decreases in alpha-activity and increases in theta power (group 2: 190%, group 3: 440%). Electroencephalographic changes were not related to changes in pain perception. For the first 30 min after ketamine injection, a dose-dependent decrease of the long-latency N150-P250 somatosensory-evoked late cortical response component was observed (group 2: 15-20%; group 3: 25-30%). Subjective pain ratings were also different between groups, with a higher degree of pain relief in group 3 for the first 30 min. At the end of the observation period, pain relief and the N150-P250 amplitude were comparable in both ketamine groups. CONCLUSIONS: These data indicate that pain relief induced by low-dose ketamine is dose-dependent for the first 30 min after bolus injection. Changes in pain perception may be quantitated by somatosensory-evoked cortical responses. Also, EEG changes are not specific for changes in nociception, but the increase in theta power may reflect the hypnotic effect of low-dose ketamine.

Adult↗

PubMed1996

Recovery from brain-stem lesions involving the nociceptive pathways: comparison of clinical findings with laser-evoked potentials.

Dissociated sensory impairment in brain-stem disorders suggests a lateral lesion involving the spinothalamic tract. Evoked potential studies of the somatosensory system with standard electrical stimulation (SEP) generally fail to establish objective correlates of such sensory deficits, because electrical stimuli predominantly activate large myelinated fibers that project into the medial lemniscal system. In contrast, laser-evoked potentials (LEPs), in response to brief radiant heat pulses, stimulate nociceptive afferents of the superficial skin and allow evaluation of thin fiber and spinothalamic tract function. We describe the recovery of deficits in pain sensitivity in five patients with isolated lateral brain-stem lesions that could be successfully monitored by LEP recordings in the acute stage and after intervals ranging from 7 months to 4 years. Upon first examination, LEPs were abnormal on the affected body side in all five cases of lateral medullary syndrome, irrespective of whether the etiology was vascular or inflammatory. The degree of recovery of pain sensitivity upon reexamination was reflected by the extent of normalization of the LEP. A control patient with vascular pontine lacunar stroke had normal LEPs on both sides, suggesting preserved spinothalamic conduction. The peak-to-peak amplitude of the main LEP component (N250-P400) correlated significantly with clinical pain sensitivity scored by standardized sensory testing (r = 0.76, p < 0.01). In contrast, early and late SEPs, after standard electrical median or tibial nerve stimulation, were normal in all patients, consistent with their intact mechanosensitivity. In conclusion, LEP studies allow the status of nociceptive function to be objectively and reliably documented on repeated examinations and therefore provide a useful supplement to multimodal sensory assessment in brain-stem disorders.

Adult↗

PubMed1996

Sensory deficits of a nerve root lesion can be objectively documented by somatosensory evoked potentials elicited by painful infrared laser stimulations: a case study.

Somatosensory evoked potentials (SEPs) in response to painful laser stimuli were measured in a patient with a unilateral sensory deficit due to radiculopathy at cervical levels C7 and C8. Laser evoked potentials (LEPs) were compared with SEPs using standard electrical stimulation of median and ulnar nerves at the wrist and mechanical stimulation of the fingertips by means of a mechanical stimulator. Early and late ulnar and median nerve SEPs were normal. Mechanical stimulation resulted in w shaped early SEPs from all five fingertips with some degree of abnormality at the fourth and fifth digits of the affected hand. Late LEPs were completely absent for stimulations at affected dermatomes and normal in the unaffected control dermatomes. The border between skin areas with normal or absent LEPs was very sharp and fitted the dermatomes of intact C6 and damaged C7 and C8 nerve roots. It is suggested that pain dermatomes are narrower than tactile dermatomes because thin fibres of the nociceptive system, activated by laser stimuli, probably do not overlap between adjacent spinal segments to the same extent as thick fibres of the mechanoreceptive system, activated by standard electrical or mechanical stimulation.

Aged↗

PubMed1996

Pruritus circumscriptus sine materia: a sequel of postzosteric neuralgia. Evaluation by quantitative psychophysical examination and laser-evoked potentials.

A case of circumscribed pruritus existing since 1 year on clinically uninvolved skin is reported, in which careful history revealed a 5-year previous episode of herpes zoster in the same dermatome. Impairment of cutaneous sensitivity was evaluated by use of a quantitative psychophysical examination and laser-evoked cortical potentials (LEP).

Aged↗

PubMed1995

Effects of menthol and cold on histamine-induced itch and skin reactions in man.

The effects of cooling and topical application of menthol on histamine-induced itch, wheal and flare reactions of the left lower arm were investigated in a threefold cross-over design with 15 healthy male volunteers. Lowering skin temperature by cooling from 32.8 +/- 0.3 degrees C to 29.7 +/- 0.5 degrees C reduced itch intensity from 260 +/- 47 units to 55 +/- 12 units (visual analogue scale) and flare diameters from 39.0 +/- 2.0 mm to 30.2 +/- 1.8 mm; wheal reactions were not affected. A similar reduction in itch was found under menthol (42 +/- 14 units) although skin temperature was not decreased. These findings suggest a central inhibitory effect of cold sensitive A-delta fibre activation on itch.

Adult↗

PubMed1995

Brain electrical source analysis of laser evoked potentials in response to painful trigeminal nerve stimulation.

Cerebral generators of long latency brain potentials in response to painful heat stimuli were identified from potential distributions in 31 EEG leads, using the brain electrical source analysis (BESA) programme in the multiple spatio-temporal dipole mode. Data were taken from a study with 10 young healthy male subjects who participated in 3 identical sessions, 1 week apart, with 4 blocks of 40 stimuli (randomized intensities above mean pain threshold). Brief infrared laser heat pulses were applied to the right temple; laser evoked brain potentials (LEPs) were averaged over 40 stimuli per block. BESA was applied to the grand mean maps averaged over the 10 subjects, 3 sessions and 4 stimulus blocks per session, as well as to the individual maps. In all cases 4 generators could consistently be identified by BESA, which were able to explain up to 98.8% of the total variance in scalp distributions at certain time intervals: dipole I with a maximum activity at 106.3 msec in the contralateral somatosensory trigeminal cortex, 19.0 mm beneath the surface; dipole II with a maximum activity at 112.1 msec at the corresponding ipsilateral area at a depth of 13.6 mm; dipole III with a maximum activity at 130.4 msec in the frontal cortex; dipole IV with 2 relative maximum activities at 150.6 and 220.5 msec, localized centrally under the vertex at a depth of 33.1 mm, which described both the late vertex negativity and the consecutive positivity. BESA applied to the individual LEP maps of each individual and session yielded again 4 major generators with sites, strengths and orientations comparable to those of the grand mean evaluations. The standard deviation (S.D.) of site coordinates within subjects was less than 3 mm for dipoles I, II and IV (5 mm for dipole III). The between-subject standard deviation was considerably larger (15 mm), which was attributed to individual differences in head geometry, size and anatomy. Dipoles I and II are assumed to be generators in secondary somatosensory areas of the trigeminal nerve system with bilateral representation, though significantly stronger in the contralateral site. Dipole III in the frontal cortex may be related to attention and arousal processes, as well as to motor cortical initiation for eye movements and muscle effects. The central dipole IV describing all late activity between 150 and 220 msec is probably a representative of perceptual activation and cognitive information processing; it was located in deep midline brain structure, e.g., the cingular gyrus.

Adult↗

PubMed1995

Laser evoked brain potentials in response to painful trigeminal nerve activation.

Long latency brain potentials were evoked by infrared laser stimuli (LEPs) applied to the right forehead in order to activate the thinnest cutaneous A-delta afferents of the upper branch of the trigeminal nerve thus inducing a painful sensation. Ten healthy male subjects participated in 4 identical subsequent sessions, one week apart, receiving 4 blocks of 40 stimuli each. This way the individual trigeminal LEPs, as well as their inter- and intraindividual reliability were determined. Five major components could be identified, denoted by polarity and peak latencies: N150, P230, N300, P360, N480. The LEP waveforms were found to be highly stable within subjects, peak latencies varied by less than 5%. Great variation in waveform appeared amongst subjects, peak latencies varied by more than 15%. The last two components exhibited the largest variability and were not identified in all subjects.

Adult↗

PubMed1993

Hypnotic hypo- and hyperalgesia: divergent effects on pain ratings and pain-related cerebral potentials.

Pain ratings and pain-related cerebral potentials in response to noxious stimuli were investigated under hypnotic hypo- or hyperalgesia. Out of a sample of 50 subjects the 10 most highly hypnotizable were selected using the Stanford Hypnotic Susceptibility Scale. Phasic pain was induced by brief electrical stimuli intracutaneously applied to the subject's left middle finger. The subjects took part in three experimental sessions. The first session was without hypnosis for familiarization with the experimental surroundings. In the two other sessions, the subjects were hypnotized and given a suggestion of analgesia or hyperalgesia with respect to pain sensation in the left hand. The sequence of hypnosis was matched within and between sessions. Pain ratings and late cerebral somatosensory evoked potentials (SEP) were used to quantify pain reactions. In addition, auditory evoked potentials (AEP) and spontaneous EEG were evaluated to differentiate between pain-specific and unspecific effects of hypnosis. Only the subjects' verbal reports of pain were drastically influenced by hypnosis: suggestion of analgesia diminished the mean pain ratings, suggestion of hyperalgesia enhanced them (P < 0.001). In contrast, the amplitudes of the late somatosensory potentials evoked by the pain-inducing stimuli were not modified in either of the suggestive states. Furthermore, no effects of hypnosis were found on AEPs and on the power spectra of the spontaneous EEG. The results are discussed on the basis of a dissociation of sensory and affective components of pain under hypnosis.

Adult↗

PubMed1992

Effects of acetaminophen and antipyrine on non-inflammatory pain and EEG activity.

Antinociceptive effects of the 2 (each 1000 mg, orally) non-steroidal anti-inflammatory drugs (NSAIDs) acetaminophen (paracetamol) and antipyrine (phenazone) were investigated with a non-inflammatory experimental pain model in 32 healthy volunteers. Phasic pain was induced by intracutaneously applied brief electrical pulses (20 msec). Pain ratings, cerebral potentials and the EEG delta power were measured in response to the stimuli. Unspecific effects upon the vigilance system were evaluated by spontaneous EEG, auditory evoked potentials and reaction times. The investigation was performed as a placebo-controlled, double-blind crossover study. Blood samples were taken to monitor the plasma concentrations of the active agents. Ninety minutes after medication the 2 NSAIDs produced similar effects upon all pain-relevant target variables, although the mean plasma concentration of antipyrine (15 micrograms/ml) was approximately twice that of acetaminophen (7.5 microgram/ml). Both NSAIDs reduced pain ratings by 6%, late cerebral potentials by 19%, and stimulus-induced delta power of the EEG by 21%. The antipyrine effects emerged earlier, in agreement with its faster kinetics. Both NSAIDs could be differentiated by their effects upon spontaneous EEG activity. Whereas acetaminophen mainly enhanced the power in the theta range, antipyrine predominantly depressed the alpha frequencies. None of the drugs influenced auditory evoked potentials and reaction times. The central effects of acetaminophen and antipyrine are discussed with respect to antinociception and decrease in vigilance.

Acetaminophen↗

PubMed1992

[The spontaneous and evoked EEG in anesthesia].

Clear differentiation between nociception and pain, or, better, between anti-nociception and pain relief, is essential for understanding the analgesic mechanisms in anaesthesia. Nociception is a neuronal activity in the pain-mediating and pain-processing nervous system, i.e. in the peripheral axons, in the spinal short cord and in certain brain structures. The nociceptive system has been well documented by experiments, especially in animals. If this system is specifically blocked, there will be no transmission and hence no sensation of pain if we leave aside the rare and complicated instances of "psychogenic pain". Nociceptive activity is blocked or at least attenuated by anti-nociceptive drugs, such as surface anaesthetics acting in the periphery by blocking the sodium channels in the conductive nerve membrane. Opiates are another example of drugs which develop an effect on specific nociceptive neurons in the spinal cord and in the brain, thus suppressing pain transmission. An ideally effective anaesthetic should act similarly, that is by specifically and selectively suppressing nociceptive activity induced by surgery. However, general anaesthesia is based on entirely different mechanisms. It lowers the arousal level, or the vigilance of the patient. Since pain is the conscious processing of nociceptive information, attenuating the vigilance also alleviates pain; there is no pain without consciousness. Most of the centrally acting analgesics will also reduce vigilance; e.g. driving is not permitted under analgesia with opiates. Alcohol is another example, although it minimally affects the nociceptive system, it substantially lowers the vigilance, thereby alleviating pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetics↗

PubMed1992

Sensory and movement-related cortical potentials in nociceptive and auditory reaction time tasks.

The processing of a sensory stimulus leading to a simple motor command was studied with scalp-recorded long latency cortical potentials in humans. Two sensory modalities were tested in their ability to activate descending motor pathways: auditory stimuli and painful cutaneous stimuli produced by a CO2 laser. Subjects were asked to react to stimuli with voluntary index finger movements. The stimulus-related and movement-related cortical potentials were recorded simultaneously with five midline electrodes on the scalp. The auditory reaction time, measured from the stimulus to the onset of electromyogram (EMG), was faster (150 ms) than the laser reaction time (350 ms). The onset of EMG of finger movements occurred only after the first negative components following auditory or laser stimuli but before the positive components. The latency from the auditory negativity to the onset of EMG was about 50 ms and the latency from the laser negativity to the onset of EMG was about 110 ms. This finding indicates that not only the peripheral afferent conduction but also central processing takes longer in a pain-related somatosensory task than in an auditory task. The frontal peak of Motor Potential (fpMP), a cortical potential related to the sensory feedback from movement, occurred with a constant latency after the onset of EMG (100 ms) and was unaffected by the task.

Adult↗

PubMed1991

Neuropharmacological analysis of synaptic transmission in the Lorenzinian ampulla of the skate Raja clavata.

Dissected ampullae of Lorenzini of the skate (Raja clavata) were studied with the aim of determining the synaptic transmitter between electroreceptor cell and afferent fibre. Resting activity and stimulus-evoked activity in response to electrical pulses were recorded in single afferent units at constant perfusion with normal and test solutions containing different putative neurotransmitters. Presynaptic transmitter release was blocked by Mg2+ (up to 50 mM) to investigate the effects of the test substances upon the postsynaptic membrane. L-Glutamate (L-GLU) and L-aspartate (L-ASP), both at concentrations between 10(-7) and 10(-3) M, enlarged strongly resting and stimulus-evoked discharge frequency in the afferent fibre. If transmission was blocked by high Mg2+, resting discharge frequency could be restored by L-GLU or L-ASP. The glutamate agonists quisqualate (10(-8)-10(-5) M) and N-methyl-D-aspartate (10(-5)-10(-3) M) enlarged spontaneous activity in the afferent fiber. The same was found for kainic acid (10(-9)-10(-5) M). Taurine at concentrations between (10(-5) and 10(-3) M caused a concentration-dependent decrease in afferent activity. The same was found for gamma-aminobutyric acid (GABA; 10(-5)-10(-4) M), and for the catecholamines adrenaline and noradrenaline, both in concentrations between 10(-5) and 10(-3) M. Serotonine (10(-5)-10(-3) M) and dopamine (10(-5)-10(-3) M) had no effect on resting or evoked activity in the Lorenzinian ampulla afferents.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1991

Effects of excitatory amino acid antagonists on synaptic transmission in the ampullae of Lorenzini of the skate Raja clavata.

1. The effects of excitatory amino acid antagonists on synaptic transmission in the ampullae of Lorenzini of the skate Raja clavata were studied. 2. At concentrations of 10(-3) to 10(-6) M. L-glutamic acid diethylester (GDEE) and L-glutamic acid dimethylester (GDME) decreased the resting afferent discharge frequency as well as the electrically evoked activities and depressed the responses to application of excitatory amino acids. 3. D-alpha-Aminoadipic acid (AA) and 2-amino-4 phosphonobutyric acid (APB) had practically no effect either on resting afferent discharge or on evoked afferent activity. 4. 2-Amino-5-phosphonovaleric acid (APV) reduced the resting afferent discharge and electrically evoked activity in the afferent fibres. APV blocked N-methyl-D-aspartate (NMDA) induced responses at a lower concentration than those induced by aspartate,. 5. Responses caused by NMDA were Mg 1(2+)-dependent; those to quisqualate (Q) application depended to a lesser degree on the Mg2+ concentration. 6. Cis-2,-3-piperidinedicarboxylic acid (PDA) blocked both the resting afferent discharge and the electrically evoked activity; it also reversibly blocked the postsynaptic, amino acid-induced responses. The L-glutamate (L-GLU) response was more resistant to the blockade than the L-aspartate (L-ASP) response. 7. Both kynurenic acid (KEN) and gamma-D-glutamylglycine (DGG) reduced the resting and evoked activities in the afferent fibres. L-ASP was more resistant to blockade by KEN than L-GLU. 8. These observations suggest a prominent physiological role of quisqualate-, kainate- and NMDA-preferring receptors in the ampullae of Lorenzini of Raja clavata.

2-Amino-5-phosphonovalerate↗

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↗