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PubMed1996

Brainstem auditory evoked potentials and somatosensory evoked potentials in prediction of posttraumatic coma in children.

Follow-up brainstem auditory evoked potential (BAEP) and somatosensory evoked potential (SEP) studies were performed within 72 hours after admission in 127 children with severe head injury (Glasgow Coma Scale score of < or = 8) in order to predict quo ad vitam outcome of posttraumatic coma. Outcomes were categorised as brain death and survival. On first assessment 50 comatose children had normal BAEPs and SEPs. 78% of them survived and 22% deteriorated and died. 45 had abnormal findings. 69% of them improved and survived whilst 31% deteriorated and died. 32 children did not have recordable BAEPs and SEPs. All of them died. Thus, comatose children with normal EP studies have in 78% good prognosis and a bad outcome can be reliably predicted.

Acoustic Stimulation↗
PubMedDate not supplied

Effects of clonazepam on paired-pulse and frequency potentiation of evoked potentials in rats.

Three different monosynaptic evoked potentials (thalamocortical, interhemispheric, i.e. transcallosal, and entorhino-dentate) were used to study the paired-pulse and frequency potentiation in adult rats. A marked potentiation was seen in both neocortical responses under control conditions (up to 200%), whereas potentiation in the dentate gyrus was only moderate. Clonazepam (0.1 and/or 1 mg/kg, i.p.) antagonized the potentiation of the thalamocortical responses only, the frequency potentiation was suppressed in a dose-dependent manner, and the paired-pulse potentiation was significantly attenuated only by the higher dose of clonazepam. The potentiation of the cortical interhemispheric as well as of the entorhino-dentate evoked potentials was not changed by either dose of clonazepam. The present results do not form the hypothesis of frequency potentiation as a mechanism of epileptogenesis.

Animals↗
PubMed1999

Normalization of auditory evoked potential and visual evoked potential in patients with idiot savant.

OBJECTIVE: To investigate the variations of auditory evoked potentials (AEP) and visual evoked potentials (VEP) of patients with idiot savant (IS) syndrome. METHODS: Both AEP and VEP were recorded from 7 patients with IS syndrome, 21 mentally retarded (MR) children without the syndrome and 21 normally age-matched controls, using a Dantec concerto SEEG-16 BEAM instrument. RESULTS: Both AEP and VEP of MR group showed significantly longer latencies (P1 and P2 latencies of AEP, P < 0.01; N1 and N2 latencies of VEP, P < 0.01/0.05), lower P2 amplitudes (P < 0.01) and higher P3 amplitudes (P < 0.01), as compared with normal controls. But none of above-mentioned changes was found with IS group. Almost all MR patients (90.1%) presented P4 component in both AEP and VEP, which was also in sharp contrast with its incidence in other 2 groups (IS: 14.3%; normal controls: 9.5%). CONCLUSION: Patients with idiot savant syndrome presented normalized AEP and VEP.

Adolescent↗
PubMedDate not supplied

Visual evoked potentials, brainstem auditory evoked potentials, and quantitative EEG in Baltic progressive myoclonus epilepsy.

Visual and brainstem auditory evoked potentials (VEP and BAEP, respectively) and quantitative EEG were studied in 16 patients with Baltic progressive myoclonus epilepsy (PME). The study demonstrated significantly delayed VEP latencies but normal amplitudes in Baltic PME. BAEPs showed slight but significant prolongation in central conduction time. Quantitative EEG revealed diminution of beta and alpha activity and accentuation of theta and delta activity. The slowing in VEP latencies is suggested to be due to impaired synaptic transmission and to reflect dopaminergic dysfunction in Baltic PME. We conclude that there is a multimodal disturbance in sensory projections to cortical areas in Baltic PME. The results give further evidence that nondemyelinating disorders--but with synaptic transmission defects--can produce changes in evoked potentials. The changes in epileptic brain are not confined to hyperexcitable epileptic neurons, but more widespread electrophysiological phenomena are produced.

Adolescent↗
PubMed1999

Menstrual cycle synchronized changes in brain stem auditory evoked potentials and visual evoked potentials.

BACKGROUND: Several studies have reported changes in the spontaneous electroencephalogram of women across the menstrual cycle (MC), raising questions on whether sensory or cognitive evoked potentials would change with MC as well. Some of these studies have found changes synchronized with MC in visual event-related brain potentials (ERPs) and brain stem auditory evoked potentials (BAEPs), whereas others have reported none. METHODS: In the present study, we attempted to study the changes in P300 component of visual ERPs, and in BAEPs across the MC in healthy women. RESULTS: The latency of P300 was longer during the ovulatory phase. Decrease across the MC phases was found for the amplitude of BAEP waves I and III, and for the wave V latency and the III-V interpeak latency. CONCLUSIONS: The results indicate that there may be a small relationship between visual ERP or BAEP and MC phase.

Adult↗
PubMed2000

The usefulness of EEG, exogenous evoked potentials, and cognitive evoked potentials in the acute stage of post-anoxic and post-traumatic coma.

Three-modality evoked potentials (TMEPs) have been used for several years in association with the EEG as a diagnostic and prognostic tool in acute anoxic or traumatic coma. Cognitive EPs have been recently introduced. EEG and cognitive EPs provide functional assessment of the cerebral cortex. TMEP parameters can be described by two indices: the index of global cortical function (IGCF) and the index of brainstem conduction (IBSC). Although it remains a unique tool for epilepsy assessment, the value of EEG is largely limited by its high sensitivity to the electrical environmental noise, its dependence on sedative drugs, and its inability to test the brainstem. Major TMEP alterations (absence of cortical activities more than 24 hours after the onset of post-anoxic coma, major pontine involvement in head trauma) are associated in all cases with an ominous prognosis (death or vegetative state). However, even if mild TMEP changes are associated with a good prognosis in 65% (post-anoxic coma) to 90% (head trauma) of cases, some patients never recover despite exogenous TMEPs that are only mildly altered in the acute stage. Thus, cognitive EPs can usefully complement exogenous EPs as a prognostic tool in coma. Indeed, even if the absence of cognitive EPs in comatose patients does not have any prognostic value, their presence implies a very high (more than 90%) probability of consciousness recovery. The major technical challenge for the future will be the development of reliable tools for continuous EEG and TMEP monitoring.

Acute Disease↗
PubMed1991

Cerebellar evoked potentials and motor evoked potentials in the spinal cord of rats.

In rats, the cerebellar evoked potentials (CEPs) were monitored along the spinal cord following the electrical stimulation of cerebellar cortex. The CEPs monitored at thoracic and lumbar cord consisted of from 1 to 3 waves with conduction velocities of 16-20.28 m/sec. The amplitudes of these waves declined dramatically as the frequency of the stimulation increased above 50 Hz, indicating that the CEPs were either evoked or conducted polysynaptically. The pathway conducting CEPs were studied using acute spinal cord lesioning and intracord recording methods. The pathways conducting CEP and MEP were also compared in the same preparation in controlled spinal-cord-lesioned animals. The CEPs were mainly conducted along the ventral and lateral funiculi where the reticulospinal tracts and the vestibulospinal tracts are located. Simultaneous disappearance of both MEP and CEP after controlled spinal cord section seems to suggest the 2 different evoked potentials are conducted along the same pathways in the spinal cord of rats. Species difference in conduction pathways of MEP and CEP were compared and discussed.

Animals↗
PubMedDate not supplied

A comparison of motor evoked potentials and somatosensory evoked potentials in patients with multiple sclerosis and potentially related conditions.

Central motor conduction (CMC) and central sensory conduction (CSC) studied by means of magnetic cortical stimulation and recording of somatosensory evoked potentials, were examined and compared in 87 patients with multiple sclerosis or potentially related conditions. In all groups of patients (either grouped by diagnosis, clinical symptomatology or disease duration) there were more aberrations in CMC compared to CSC. This difference became statistically significant when all patients were taken together. By both methods we were able to detect signs of clinically silent lesions and these were often restricted to either of the pathways.

Adolescent↗
PubMed1982

Influences on drugs on evoked potentials in the cat cerebellum: I. Effects of CNS depressants and stimulants on the cerebellar afferent pathways.

The effects of drugs on the potentials evoked by electrical stimulation on the sensorimotor area (SMA), nucleus reticularis tegmenti pontis (PTRN), nucleus reticularis lateralis (LRN), nucleus olivaris inferior (ION), or superficial radial nerve (SR) were investigated in cat cerebellar cortices. Pentobarbital-Na decreased the amplitude of the potentials evoked by all stimulations at every recording site. Pentobarbital-Na remarkably decreased the SMA- or PTRN-stimulation induced evoked potentials in the anterior lobe. Chlorpromazine decreased the amplitude of the potentials evoked by SMA stimulation on the anterior lobe and ipsilateral crus l, and the drug increased it on the posterior lobe and contralateral crus l. With precerebellar nuclei stimulations, chlorpromazine decreased the amplitude of the evoked potentials in cerebellar cortices, whereas SR stimulation-evoked potentials were remarkably increased in amplitude. Meprobamate increased the amplitude of the potentials evoked by precerebellar nuclei or SR stimulation at an early stage and then decreased it. Caffeine, picrotoxin, and strychnine remarkably increased the amplitude of the potentials in cerebellar cortices evoked by all stimulations. Strychnine in particular significantly increased the amplitude of the potentials evoked by SR stimulation. These results strongly indicate that CNS depressants and stimulants affect the cerebellar afferent pathways, probably in an indirect manner.

Animals↗
PubMed1997

Differential changes of laser evoked potentials, late auditory evoked potentials and P300 under morphine in chronic pain patients.

The present study investigates the differential behavior of laser evoked brain potentials (LEPs), late auditory evoked potentials (AEP) and the endogenous P300 in response to morphine treatment, examined in 6 chronic pain patients. The main result was that in parallel with marked clinical pain relief, amplitudes of the long latency LEP positivity (P400) were significantly reduced under morphine. One patient suffering from extremely painful osteoporosis for 20 years exhibited a large middle latency component (N170) which was prominently attenuated by morphine. In contrast to LEP amplitude reductions, auditory N1 and P2 potentials appeared either unchanged or even enlarged during morphine treatment. Also P300 amplitude was slightly increased under morphine. Reaction time and mood scales also failed to indicate any sedation. Obviously, LEPs reflected specifically the analgesic morphine effect in this study, while stability or enhancement of AEPs and P300 during morphine treatment indicated lack of sedation or even improved perception and concentration due to the removal of persistent pain as a disruptive perceptual-cognitive stressor.

Adult↗
PubMed1984

The relationship between flash evoked potentials and evoked amplitude modulation patterns of an applied UHF electromagnetic field in the rat.

Pilot studies demonstrate evidence that the electrophysiological processes associated with flash stimulation of the central nervous system (CNS) of rats, as seen in the recordings of visual-evoked potentials, may also be detectable using an ultrahigh frequency electromagnetic field (UHFEMF). Patterns of amplitude modulation of an applied UHFEMF, when recorded and averaged, show strong correlations with simultaneously recorded evoked potentials. The data support the hypothesis that the UHFEMF amplitude is altered in a dynamic fashion by the tissue's electrophysiological processes that are involved with the generation of CNS electric fields.

Animals↗
PubMed1996

Differences in sensitivity between magnetic motor-evoked potentials and somatosensory-evoked potentials in experimental spinal cord lesions.

STUDY DESIGN: Graded posterior spinal cord compression and partial sectioning of the spinal cord were performed, and magnetically induced descending spinal cord potentials were recorded. OBJECTIVES: To compare the sensitivity of transcranial magnetic motor-evoked potentials in the spinal cord and other spinal cord evoked potentials to spinal cord lesions. SUMMARY OF BACKGROUND DATA: Somatosensory-evoked potentials have been the standard technique for monitoring spinal cord function during spinal surgery. These potentials, however, do not necessarily reflect descending motor tract function. Transcranial electric or magnetic stimulation for motor-evoked potentials is a more direct measure of motor tract function. However, more research on magnetic motor-evoked potentials is needed. METHODS: Fifteen adult cats were used. Graded posterior spinal cord compression was performed at L2 in 10 cats, and partial sectioning of the spinal cord was performed at L2 in five cats. The location sequence of lesioning was dorsal column section, dorsal 1/2 section, dorsal 2/3 section, and total spinal cord section. Magnetic motor-evoked potentials were recorded by epidural catheter electrodes placed above at, and below the lesion. Electric motor evoked potentials and spinal and cortical somatosensory-evoked potentials were recorded serially for a comparison of their sensitivity to spinal cord dysfunction. RESULTS: In posterior spinal cord compression, N1 amplitude of magnetic motor-evoked potentials at and below the lesion decreased after 1 minute of compression with a 70 g weight, and N1 and N2 amplitude disappeared after 1 minute of compression with a 100 to 120-g weight. Electric motor-evoked potentials changed at amplitudes comparable with those shown by magnetic motor-evoked potentials. Spinal somatosensory-evoked potentials showed the most sensitive changes to spinal cord posterior compression and disappeared after 1 minute of compression with 80 g Cortical somatosensory-evoked potentials in five cats were not sensitive enough for spinal cord posterior compression injury and did not disappear even after 1 minute of compression with 120 g. In magnetic motor-evoked potentials, after dorsal hemisectioning of the spinal cord only N3 disappeared; N1 and N2 disappeared after ventral spinal cord sectioning in spinal somatosensory-evoked potentials, amplitudes decreased after dorsal column sectioning, and all negative peaks disappeared after dorsal hemisectioning of the spinal cord. CONCLUSIONS: Posterior compression injuries are diagnosed more easily with spinal somatosensory-evoked potentials. Motor-evoked potentials were slightly less sensitive, but they were significantly more useful in diagnosing posterior compression injuries than were cortical somatosensory-evoked potentials.

Animals↗
PubMed1992

Spermine facilitates the generation of long-term potentiation of evoked potential in the dentate gyrus of anesthetized rats.

The effects of the polyamines, spermine, spermidine and putrescine, on long-term potentiation (LTP) of evoked potential were investigated in the dentate gyrus of anesthetized rats. Injection of 5 nmol spermine into the lateral ventricle did not influence the basal amplitude of the population spike, but significantly enhanced the potentiation induced by subthreshold tetanic stimulation (20 pulses at 60 Hz). The effect of spermine resulted in facilitation of LTP generation. Injection of the same dose of spermidine or putrescine affected neither the basal response nor the potentiation induced by subthreshold tetanus at all, indicating that the LTP-facilitating effect is specific to spermine. Furthermore, the LTP-facilitating effect of spermine was dose-dependent in the range of 0.5-50 nmol. When 5 nmol ifenprodil, an antagonist at the polyamine site of the NMDA receptor channel complex, was concomitantly injected, spermine could not facilitate the generation of LTP. Since injection of ifenprodil alone did not influence the generation of LTP, it is probable that ifenprodil specifically blocks the effect of spermine. These results suggest that spermine facilitates the generation of hippocampal LTP, probably through an ifenprodil-sensitive polyamine site associated with the NMDA receptor.

Adrenergic alpha-Antagonists↗
PubMed1997

Brain stem evoked potentials and visual evoked potentials in relation to the length of occupational exposure to low levels of toluene.

In 49 printing-press workers occupationally exposed to toluene for approximately 21.6 years, the values of BEAP and VEP parameters were examined in relation to the length of exposure. With the exception of P2 wave, there was a significant increase in the latencies of all the BEAP waves examined as well as in the interpeak latency (IPL) P3-P4, whereas IPL P4-P5 decreased significantly with the length of exposure. The amplitude of all the VEP examined decreased significantly with the length of exposure. Toluene exposure was evaluated by measuring the concentration of toluene in peripheral blood and of hippuric acid in urine on Wednesday morning prior to the workshift, and of hippuric acid in urine after the workshift on the same day. According to the average concentration of hippuric acid in urine after the workshift, the levels of toluene exposure were estimated to range from 40-60 ppm. Evoked potentials were determined on Mondays 10-12 hours after a nonworking weekend.

Adult↗
PubMed1996

Brainstem auditory evoked potentials and visually evoked potentials in young patients with IDDM.

OBJECTIVE: To investigate whether young IDDM patients develop central nervous dysfunction and to establish a possible relationship with various disease parameters. RESEARCH DESIGN AND METHODS: Thirty-two patients, aged 13.5 +/- 2 years, with disease duration of 6 +/- 2.6 years and age of onset of 7.7 +/- 3.2 years (group 1), and 21 patients with short-term disease, age 9.7 +/- 3.5 years, duration of disease < 2 years and age of onset of 9.4 +/- 3.3 years (group 2) were compared with age- and sex-matched control subjects. Exclusion criteria were clinical signs of neuropathy, retinopathy, nephropathy, or hearing impairment. Neurophysiological studies included auditory and visually evoked potentials (EPs). RESULTS: Patients in group 1 revealed increased P100 latencies of visually EPs (103.4 +/- 4.5 vs. 96.8 +/- 3.7 ms) and interpeak latencies I-V of auditory EPs (4.16 +/- 0.10 vs. 3.99 +/- 0.09 ms) and had abnormal latencies (values outside 2.5 SD) in 37%. However, short-term patients (group 2) had results within normal limits compared with control subjects. In group 1, longer disease duration and younger age at onset correlated with an increase of P100 latency (P < 0.001) and IPL I-V (P < 0.001). Patients with a history of severe hypoglycemic episodes had increased latencies compared with patients without hypoglycemia (P < 0.05). Furthermore, metabolic control during the last 2 years was related to P100 latencies (P < 0.05). CONCLUSIONS: EPs noninvasively detect subclinical central nervous system involvement in children and adolescents with IDDM. Most important risk factors are duration of disease and frequency of severe hypoglycemia.

Acoustic Stimulation↗
PubMed2000

Comparison of spinal cord evoked potentials and peripheral nerve evoked potentials by electric stimulation of the spinal cord under acute spinal cord compression in cats.

STUDY DESIGN: Spinal cord evoked potentials and peripheral nerve evoked potentials after spinal cord stimulation were recorded under acute spinal cord compression in 19 cats. OBJECTIVES: To investigate the effects of acute compression upon grey matter and white matter by comparing both potentials. METHODS: We compared peripheral nerve evoked potentials, recorded at the biceps brachii branch of the musculocutaneous nerve, with descending spinal cord evoked potentials, recorded from the lumbar spinal cord, by stimulation to the C2 level, under compression of the C6 segment. RESULTS: The amplitude of both potentials decreased with increased compression. The second wave of peripheral nerve evoked potentials, which are motor fibre action potentials, decreased sooner than those of the spinal cord evoked potentials. CONCLUSION: These findings indicate that peripheral nerve evoked potentials are sensitive to acute damage of the segmented compression. This suggests that grey matter is more vulnerable to compression than white matter.

Animals↗