Biomedical subjects

R Callieco

Publications and source records attributed to R Callieco.

17 recordsLinked to original sources

PubMed1992

Multimodal evoked potentials in myotonic dystrophy (MyD).

By means of multimodal evoked potentials (EPs), we evaluated the central nervous system (CNS) involvement in 25 subjects suffering from myotonic dystrophy: brainstem auditory evoked potentials (BAEPs), middle-latency auditory evoked potentials (MLAEPs) and somatosensory evoked potentials (SEPs) from the upper limb were performed on all subjects, whereas only the 19 patients, whose clinical ocular abnormalities were slight, underwent pattern-electretinograms (PERGs) and pattern visual-evoked potentials (VEPs) in order to identify the site of lesion among visual pathways (retinal and/or retroretinal). PERGs were abnormal in 8/19 subjects, VEPs in 8/19 subjects (the two techniques were simultaneously abnormal in 8 eyes), BAEPs in 7/25 subjects, MLAEPs in 4/25 subjects (in one subject both BAEps and MLAEPs were abnormal) and SEPs were abnormal in 1/25 subjects. 13/25 of our subjects showed at least one EP that revealed a CNS involvement. The electrophysiological alterations were not correlated either with subject age or with disease duration. Multimodal EPs enabled us to demonstrate that CNS involvement in myotonic dystrophy is important and mainly affects the visual and auditory system.

Adult↗

PubMed1992

Spinal and cortical potentials evoked by tibial nerve stimulation in humans: effects of sex, age and height.

Somatosensory evoked potentials by posterior tibial nerve stimulation at the ankle were performed in 74 healthy volunteers (36 females and 38 males) aged 14-76 years. Cortical potentials were obtained in all subjects and spinal potentials (N22) in 71 subjects. All parameters were related to subject's age, height and sex. Sex influenced only P40-N50 amplitude, which was greater in females. All latencies of spinal and cortical components increased in a similar manner with subject's height (about 0.16-0.18 ms per cm), whereas the N22-P40 interpeak latency was independent from height, but related to T12-Cz distance. Absolute latencies of the spinal and of most cortical components, but not interpeak latencies, increased with subject's age (about 0.06-0.09 ms per year). The parameters to compute normative data (according to univariate or bivariate regression models) are furnished. Limits of right-left differences are reported.

Adolescent↗

PubMed1992

A one-week test-retest reliability study of Brainstem Auditory Evoked Potentials.

Brainstem Auditory Evoked Potentials (BAEPs) are increasingly used in longitudinal evaluation of brainstem function. The reliability of the neurophysiological parameters and definition of the normal test-retest variability are required for such investigations. In the present study we submitted 20 healthy volunteers (10 males and 10 females; mean age 35.1 years, range 24-49) to BAEPs in two sessions separated by seven days. The reliability of the parameters was estimated by means of intraclass correlation coefficient (R). All BAEP parameters showed excellent R values (above 0.75). In addition, the confidence interval lower limits of all R coefficients had good to excellent values. Finally we computed the upper normal limits of the test-retest variability of each parameter, with alpha = 0.01, using the within-subjects mean square. The confirmed good reliability of the analyzed parameters enables us to employ BAEPs as useful monitoring instruments in longitudinal studies.

Adult↗

PubMed1991

Multimodal evoked potentials in progressive external ophthalmoplegia with mitochondrial myopathy.

Multimodal evoked potentials were studied in 13 patients affected by progressive external ophthalmoplegia with histologically proven mitochondrial myopathy. Progressive external ophthalmoplegia occurred with craniosomatic spreading in all the patients and with a varying degree of nervous and/or other system involvement in most of them. In all but one of the subjects, at least one evoked potential modality was abnormal; 11 of them demonstrated an abnormal visual evoked potential, but this finding might have been influenced by concurrent retinal dysfunction. Abnormalities in brainstem auditory evoked potentials and/or somatosensory evoked potentials, revealing an impairment of central sensory pathways, were detected in 7 subjects, 5 of whom lacked clinical evidence of central nervous system involvement. Thus, evoked potentials represent an useful tool for the detection of subclinical central nervous system involvement in patients affected by progressive external ophthalmoplegia with mitochondrial myopathy.

Adult↗

PubMed1991

Evoked potentials monitoring of a cerebral focal ischemia model.

A model of cerebral ischemia by microsphere embolization in the rabbit was monitored with somatosensory evoked potentials by median nerve stimulation (SEPs) and by flash visual evoked potential (VEPs). The degree of SEP alterations paralleled the type of lesions (focal or multifocal ischemia or diffuse oedema). Alterations present at the first hour after ischemia were generally unchanged during the follow-up, which ended at the 24th hour. The prevalence of VEP alterations was low (only 16% in focal ischemia). These results are compared to EEG modifications performed in the same animals.

Animals↗

PubMed1991

Somatosensory evoked potentials by electrical stimulation of the third trigeminal branch in humans.

Somatosensory Evoked Potentials by stimulation of the trigeminal nerve (TSEPs) were recorded from 30 healthy subjects (15 males, 15 females; mean age: 45.2 years; range: 21-66 years) in order to assess normative data for clinical purposes. To elicit the TSEPs, electrical square pulses (duration: 0.1 msec; frequency: 3.3 Hz; intensity: 4-6 mA) were delivered by bipolar skin electrodes (cathode over the foramen mentale and anode on the middle of the chin, stimulating the trigeminal third branch). TSEPs were obtained from C3-Fpz and C4-Fpz by twice averaging 1000 responses. Time base was 100 msec; bandpass filter setting was 5-1500 Hz. In our normal subjects the TSEPs were composed of several components (N1, P1, N2, P2 and N3); the components, with the exception of N3, were always bilaterally detectable. Statistical analysis (repeated measures analysis of variance) demonstrated a dependence of TSEP latencies on sex; it did not demonstrate an analogous dependence on either side of stimulation or age. Finally, we propose some guidelines for the evaluation of TSEPs: consider N1, P1, N2 and P2 waves, base the judgement of normality on latencies rather on amplitudes, use differing normative data according to sex.

Adult↗

PubMed1991

Visual evoked potentials in the white New Zealand rabbit: source localization and normative aspects.

Normative data of visual evoked potentials were obtained from occipital screw electrodes referenced to a nasal electrode in 10 white New Zealand rabbits. Two time-bases were used (200 and 400 ms) in order to reliably identify both early components (of retinal and cortical origin), as well as late components. The putative origin of the single components was established by simultaneous recording of ERG and by stereotaxic recordings from the lateral geniculate body. Test-retest variability was measured repeating the recordings after 24 hours.

Animals↗

PubMed1991

Brainstem auditory evoked potentials in the rabbit.

Eight white New Zealand rabbits were submitted to auditory stimulation in order to obtain normative BAEP parameters. A monaural alternating 0.1 ms click stimulation at 20 Hz, 90 dB was used. Two series of 1000 responses were averaged (10 ms time-base, 160-3000 Hz band-pass) and highly reproducible peaks were obtained. Peaks P1, P2, P3, P4 were obtained in all ipsilateral recordings, whereas peak P5 was detectable in only 6 animals. In contralateral recordings P1 was absent and the following peaks were similar to those of ipsilateral recordings. Normative values of absolute and interpeak latencies, peak amplitudes and amplitude ratios were obtained. The procedure was repeated 24 hours after basal recordings and measures of test-retest variability were obtained.

Animals↗

PubMed1991

Prestimulus EEG influence on late ERP components.

Ten healthy volunteers were submitted to an auditory oddball event related potentials (ERP) paradigm. Single trial 500 ms poststimulus ERPs (Pz, Cz, Fz--linked earlobes) along with the correspondent 1000 ms prestimulus EEG (O1-Cz) were stored. EEG epochs were submitted to spectral analysis and a slow wave index (SWI = delta + theta/total) was computed. Three selective ERP averages corresponding to low, medium and high SWI were computed. N2 latency was longer and P3a amplitude was lower in high SWI averages as compared to low SWI averages.

Analysis of Variance↗

PubMed1991

Effect of repetition rate on middle latency auditory evoked potentials in humans.

Middle Latency Auditory Evoked Potentials (MLAEPs) were recorded from 15 healthy subjects in order to evaluate the influence of different repetition rates on the latency and the amplitude of their main components Na, Pa and Nb. MLAEPs were obtained from Cz-ipsilateral ear lobe by averaging responses to 2000 monaural clicks delivered to both ears, at 65 dB SL of intensity, for each of 3 different repetition rates (1.1, 4.1, 8.1 Hz). Time base was 100 ms, analogical band-pass filter 5-1000 Hz (off-line digital bandpass: 20-100 Hz). The statistical analysis (repeated measures analysis of variance), demonstrated that, the latency and the amplitude of the Nb component were slightly influenced by repetition rate while Pa and Na were not. Moreover Nb showed the greatest interindividual variability (as already pointed out by other authors too); thus, we suggest that a stimulus rate of 8.1 Hz and the analysis of Na and Pa component only, can be regarded as the best assessment for MLAEPs evaluation when they are used for clinical purposes.

Adult↗

PubMed1991

Effect of stimulus mode on middle latency auditory evoked potentials in humans.

Middle Latency Auditory Evoked Potentials (MLAEPs) were recorded in 35 healthy subjects; all underwent monaural stimulation and 18 of them additionally underwent binaural stimulation. The aim of the study was to determine the effect of stimulus mode on MLAEP Na, Pa and Nb components and to assess normative data for clinical purposes. MLAEPs were respectively obtained from Cz-ipsilateral ear lobe (monaural mode) and from Cz-A1 and Cz-A2 (binaural mode) by twice averaging 1000 responses to 65 dBHL alternating clicks delivered at a repetition rate of 8.1 Hz. Time base was 100 msec; analogical band-pass filter setting was 5-1000 Hz (off-line digital badpass: 20-100 Hz). The statistical analyses (paired t-test, repeated measures analysis of variance) were not able to demonstrate any differences that derived from differing sides of stimulation (monaural mode) or from differing recording derivations (binaural mode); on the contrary, we demonstrated a slight increase in waveform amplitudes when the binaural mode was employed. In particular, we observed an increase in Na-Pa peak-to-peak amplitude, whereas Pa-Nb amplitude was unmodified. This finding is explicable in terms of a binaural interaction effect. Finally, we propose some guidelines for the correct performance and evaluation of MLAEPs in clinical practice.

Acoustic Stimulation↗

PubMed1991

Multimodal evoked potentials in diabetics.

In the present study we performed brainstem auditory evoked potentials, pattern electroretinogram and visual evoked potentials for the identification of a subclinical involvement of central auditory and visual pathways in diabetes mellitus. We tested 30 patients, and a neurophysiological central nervous system involvement was demonstrated in 23.3% of them. The mean values of patients and controls were significantly different for most of the evoked potential parameters. Some of these parameters were linearly related with duration of the disease, clinical score and peripheral nerve conduction velocities.

Adult↗

PubMed1989

Somatosensory evoked potentials in Charcot-Marie-Tooth disease.

SEPs by median nerve stimulation have been performed in 18 adult patients (12 males and 6 females) affected by CMTD (type I, 13 patients; type II, 5 patients). All patients underwent MCV studies (median, ulnar, peroneal nerve), SCV studies (median and sural nerve), VEP, BAEP. N9 and N13 peaks were not detectable in 7/13 and 5/13 cases (HMSN type I) while cortical N19 were always recorded. Latency values of all responses were moderately or markedly delayed in all cases with HMSN type I, but proved normal or slightly delayed in HMSN type II cases. The prolonged latencies were mainly related to slowing of peripheral conduction. N9-N13 inter-peak was abnormally prolonged in 2 cases and N13-N19 in 2 other cases; both were prolonged in another case. In another 3 cases an abnormal BAEP was recorded. The few patients with abnormal CCT and BAEP probably belong to a borderline form between HMSN and hereditary ataxias.

Adult↗

PubMed1988

Prestimulus spectral EEG patterns and the evoked auditory vertex response.

A vigilance-related index (slow wave index, SWI) representing the relative delta + theta amplitude of the 1 sec prestimulus EEG spectrum has been related to latencies and amplitudes of the auditory cortical evoked response (EP) in 12 volunteers. Stimuli were 70 dB SL tone bursts delivered at 10 sec ISI. Four selective averages were obtained for each subject according to the subdivision of the SWI into quartiles. The subjects were divided into 2 groups having individual mean SWI values above or below the group's median SWI. Repeated measures MANOVA showed that N1 latency increased within subjects from the first to the fourth SWI quartile and that it was longer in subjects with high mean SWIs. N1-P2 amplitude decreased within subjects from the first to the fourth SWI quartile, but only in the group with high mean SWI.

Adult↗

PubMed1979

[Visual evoked potential in multiple sclerosis].

Visual Evoked Responses (VER) by binocular flash stimulation were carried out in 30 cases of "definite" (15 cases-Group I) and of "probable" (15 cases-Group II) Multiple Sclerosis (MS). VER were recorded bilaterally by reference occiput-mastoid. Averaging of 50 responses (time base 200-500-1000 msec) was considered; measures were made by registration on X-Y Plotter. Abnormal VER by increased latencies of III and/or IV peak (Ciganek) were present uni- or bilaterally in most of the subjects (73,3% of the I Group; 66,6% of the II Group). Percentage of abnormal VER is quite higher than clinical involvement of visual pathways; it is present in 3 out of 5 patients also, in whom clinical findings were confined to spinal cord. The results are discussed with reference to the previous literature. Recording of VER seems useful in detecting involvement of visual pathways without clinical evidence.

Adult↗

PubMedDate not supplied

Middle latency auditory evoked potentials improve the detection of abnormalities along auditory pathways in multiple sclerosis patients.

Brain-stem and middle latency auditory evoked potentials (BAEPs and MLAEPs) have been studied in 34 multiple sclerosis (MS) patients. We were able to detect a central nervous system auditory pathway involvement in 17 (50%) of the patients: 38% by BAEPs alone (I-V inter-peak latency) and 47% by MLAEPs alone (Na and Pa peak latency). Five patients had abnormal MLAEPs with normal BAEPs whereas the opposite was detectable in only 1 patient. In addition, most MLAEP parameters in the MS group statistically differed from those obtained in the control group. Therefore, our results demonstrated that the auditory pathway impairment could frequently be located at a rostral level along the auditory radiation. In conclusion, even if only Na and Pa components were considered, MLAEPs succeeded in improving the sensitivity of the auditory evoked potential examination without increasing the false positive rate.

Acoustic Stimulation↗

PubMedDate not supplied

Reliability and upper normal variability limits of pattern reversal visual evoked potential parameters.

Twenty healthy volunteers aged 21-48 years (10 males, 10 females) were submitted to pattern reversal visual evoked potentials with 15' and 30' checks. The recordings were repeated after 7 days to assess reliability and upper normal variability limits of the following parameters: latencies of N70, P100, N140 and peak-to peak amplitudes of N70-P100, P100-N140. Reliability was tested with intraclass correlation coefficient, which was excellent or good for all parameters. Test-retest variability limits were computed with = 0.01 for absolute latency differences and relative amplitude differences.

Adult↗