Biomedical subjects

A Taghavy

Publications and source records attributed to A Taghavy.

At least 19 recordsLinked to original sources

PubMed1995

Symptomatic and asymptomatic high-grade unilateral internal carotid artery stenosis: scalp topography of event-related potentials (P300) and psychometric testing.

Unilateral internal carotid artery (ICA) stenosis may be accompanied by widespread atherosclerosis of extra- and intracranial vessels leading to subtle cognitive disorders. We applied multichannel recording of P300 in 28 patients (68.3 +/- 8.1 years; 15 asymptomatic, 13 with a history of transient ischemic attack (TIA)) and compared them with an age- and sex-matched control group. All underwent a visual "odd-ball paradigm" as well as a psychometric test, the Cognitive Performance Test (CPT), testing mainly visual attention and memory. The potentials were derived from 16 electrodes according to the 10/20 system against linked mastoids. The latencies and amplitudes of N250 and P300 were measured and their amplitudes additionally mapped. Furthermore, the early sensory exogenous potentials, P1 and N1, within the P300 potentials as well as conventional pattern reversal visual evoked potentials (PVEPs) were evaluated. (1) Both the early exogenous potentials and the conventional PVEPs showed no significant differences among all groups. (2) There were no significant differences between asymptomatic patients and those with a TIA history in all parameters of the P300 complex so that one total patient group was constructed and compared to the controls. (3) Patients' P300 amplitudes showed significant reductions over hemispheres ipsilateral (P < or = 0.014) and contralateral (P < or = 0.044) to the stenosis. (4) The N250 amplitudes were reduced only in the central leads (P < or = 0.05). (5) The latencies of N250 potentials were significantly prolonged at many electrodes, not only ipsi-(P < or = 0.0007) but also contralateral (P < or = 0.022) to the stenosis. (6) The patients' P300 latencies showed significant lengthening only at occipital sites (P < or = 0.05) compared to controls. (7) In all measured parameters, within the patient group, the differences between hemispheres ipsilateral versus contralateral to the ICA stenoses did not reach statistical significance. (8) The CPT values detected slight cognitive disorders for both patient groups and they correlated significantly with the latencies in many leads. (9) The highest test sensitivity to classify patients versus controls (z score > 2) was reached in P300 maps of TIA patients (77%). An altered P300 indicates electrophysiologically, and CPT behaviorally, subclinical cognitive deficits even in asymptomatic patients with unilateral tight ICA stenoses. Interestingly, no differences between asymptomatic and TIA patients with a high-grade unilateral ICA stenosis could be found.

Aged↗

PubMed1994

Dynamics of cognitive brain dysfunction in patients with cirrhotic liver disease: an event-related P300 potential perspective.

The dynamics of cognitive brain functions of 104 patients with both chronic non-cirrhotic (NC) and cirrhotic liver disease (C: C1, non-encephalopathic; C2, encephalopathic) were investigated by means of visual P300 potentials elicited in both the paradigms of transient (PI) and selective attention (PII). Conventional PVEPs, psychometric tests and quantitative liver function tests were also performed. As compared to both an age-matched control group (N) and the non-cirrhotic patients (NC), the N250 and P300 latencies of the cirrhotics (C) were equally prolonged in both P300 paradigms (P = 0.0001). By contrast, the P300 amplitudes were not different between the patient groups in either P300 paradigm. In the cirrhotics, however, the P300 amplitude differences between PII and PI (+ 3.7 +/- 2.8 muV, mean +/- 1 S.D.) were significantly (P < 0.01) smaller than in the non-cirrhotics (+ 7.5 +/- 5.2 muV) reflecting disturbances in the dynamics of visual attention. Interestingly, these P300 amplitude differences between both paradigms were positively correlated (r = 0.35; P = 0.005) with hepatic metabolic capacity, but not with liver blood flow (r = 0.23; P > 0.05). The diagnostic efficacy of the visual P300 in PI (sensitivity, 48%; specificity, 100%) was lower than that of the visual P300 in PII (79%; 100%) and that of the psychometric tests (63%; 94%), but it remained superior to that of the PVEPs (29%; 97%). It is concluded that in patients with cirrhotic liver disease visual P300 potentials can even reveal the dynamics of minor cognitive brain dysfunction and may also provide interesting pathophysiological information.

Adult↗

PubMed1993

The event-related P300 potential analysis of cognitive human brain aging: a review.

Event-related P300 potentials are closely reflecting cognitive functions such as stimulus evaluation time (P300 latency) and task relevance (P300 amplitude). Hence, both their potential clinical application for detecting slight cognitive disturbances and an increasing interest in the aging of cognitive human brain functions resulted in a growing number of studies on age-related P300 changes. Although there are converging lines of evidence that aging results in prolongations of P300 latencies, reductions of P300 amplitudes and a more equipotential P300 scalp distribution, the amount of these changes and the best fit for the P300-age interactions, respectively, remain still controversial. In general, these P300 alterations obviously reflect only minor cognitive changes during normal aging. For their clinical application, however, it is necessary to obtain an age-matched normative database. Furthermore, the increased P300 variability in the elderly has to be reduced--as far as possible--by appropriate simple P300 paradigms which should be preferentially applied in longitudinal analyses to differentiate normal from pathological aging of cognitive functions. Finally, additional cross-correlational analyses between the P300 and morphological as well as neurobiochemical data are needed. By these means, our knowledge about age-related changes of cognitive brain functions should be considerably enlarged.

Adolescent↗

PubMed1993

[Oculomotor paralysis as the leading symptom of meningovascular syphilis. Report of two patients and review of the literature].

A brain stem infarction in the area of the nerve fascicle of the oculomotor nerve could be demonstrated by NMR to be the cause of a complete oculomotor nerve palsy in a patient with neurosyphilis. A second case presented the very rare finding of an isolated bilateral incomplete oculomotor nerve paresis with external paresis on the right and internal paresis on the left side.

Brain Stem↗

PubMed1992

Visual event-related P300 potentials in early portosystemic encephalopathy.

Visual event-related P300 potentials, conventional visual evoked potentials, and psychometric tests were applied to patients with noncirrhotic chronic liver disease and to clinically nonencephalopathic and encephalopathic cirrhotics to compare their diagnostic efficacy in detecting early portosystemic encephalopathy (PSE). Sixty-four investigations were performed in 58 patients. The latencies of the P300 parameters were significantly longer in both the encephalopathic and nonencephalopathic cirrhotics than in the noncirrhotics, indicating distinctly abnormal cortical processing of visual stimuli in cirrhotic patients. The visual P300 potentials showed the highest sensitivity and specificity for grade I PSE. Abnormal P300 test results were also found in 78% of the clinically nonencephalopathic cirrhotics, while psychometric tests showed abnormalities in only 41%. The P300 latencies were similar in alcoholic and nonalcoholic cirrhotics. Significant inverse correlations were found between the P300 latencies and measures of quantitative liver function such as galactose-elimination capacity and aminopyrine breath test. It is concluded that visual event-related P300 potentials are a sensitive index of subclinical and grade I PSE. Furthermore, the degree of cognitive dysfunction detected by this method in patients with liver cirrhosis appears to be related to the reduction in hepatic metabolic capacity.

Adult↗

PubMed1992

Pattern reversal visual evoked potentials (PVEPs) in transient ischemic attacks (TIAs) and prolonged reversible ischemic neurological deficits (PRINDs) of anterior circulation with normal EEGs and normal cranial CTs.

Out of 75 patients with TIA or PRIND we selected 9 TIAs and 6 PRINDs with normal EEGs and CCTs, full recovery of neurological function, no history of amaurosis fugax and no findings of visual impairments. PVEPs were derived from 01-02 to Fz and Cz as ground following binocular pattern reversal visual stimuli of 1.9 Hz. Interhemispheric differences of the latencies of P60, N80, P100 and of the amplitudes N80/P100 and P100/N140 were compared with the corresponding parameters of 22 age matched controls. In contrary to the latency differences the interhemispheric difference of the amplitude N80/P100 was highly significantly larger (33.5 +/- 16.0%) in patients than in the control group (12.8 +/- 9.8%) (p < or = .0005). The amplitude P100/N140 behaved the same way (p < or = .025); the amplitude of the affected side being smaller. There were no statistical differences between TIAs and PRINDs and a tendency was seen for normalization of the differences with increasing time distances between the onset of the ischemic attack and the point of time of the recordings.

Adult↗

PubMed1992

Parenchymal "damage" in transient ischemic attacks (TIAs) and prolonged reversible ischemic neurologic deficits (PRINDs):--the role of cranial CT and EEG.

Over a period of 6 years (1985-1990) we reviewed records of patients with one or more TIAs or PRINDs (196 TIAs, 63 PRINDs). 111 patients (42.9%) suffered from TIAs/PRINDs of the anterior circulation. In all cranial CT scanning (CCT) was performed, whereas only in 79 EEG was recorded after recovery from the symptoms. 25 patients (22.5%) out of the 111 showed low density areas of recent onset in CCT made responsible for the attack. Among the EEGs of the 79 patients 35 (44.3%) revealed corresponding electrical abnormalities. Out of the 79 patients investigated by both methods in 14 (17.7%) a lesion was demonstrated in CCT and focal abnormality in EEG. In 11 (13.9%) EEG was normal despite a lesion manifested in CCT. Vice versa 21 patients (26.6%) showed normal CCTs but focal abnormalities in EEG. By far most cases (43%) had normal CCTs and EEGs. These results may contribute to a redefinition of TIA and PRIND as clinically defined syndromes in prae-CT-area.

Amnesia↗

PubMed1991

[Visual P300 in acute hepatic encephalopathy resulting from non-A-non-B fulminant hepatitis: analysis of the course before and after orthotopic liver transplantation].

The method of Pattern Flash elicited P300 (PFP300) has been applied to evaluate the dynamic alterations in cognitive function of a 58 year old woman (H. C.) presenting with hepatic failure due to fulminant hepatitis Non-A-Non-B. At the time of the first investigation she complained about slight memory deficits and revealed signs of hepatic encephalopathy grade I according to Parson-Smith et al. (bilirubin 26.0 mg/dl, NH3 102 micrograms/dl, electrolytes and blood sugar normal). Psychometric tests: Number connection test (NCT): 54 s (28-53 s, greater than 2sd); Syndrom-Kurz-Test (SKT): total score = 9 (0-4), compatible with a slight "organic brain syndrome". PFP300: N250 latency 343.5 ms (276.4 +/- 14.7 ms, greater than 4sd); PFP300-latency: 442.5 ms (326.9 +/- 14.7, greater than 7sd); PFP300 amplitudes: 16.0 microV (14.4 +/- 8.4, +/- 1sd), indicating severe disturbance in visual discrimination without visual attention deficits. Due to progressive deterioration of liver function the patient had to undergo orthotopic liver transplantation. The patient was reinvestigated four weeks later. The clinical and laboratory status were normal and no signs of hepatic encephalopathy could be detected clinically or by means of the psychometric tests. The parameters of the PFP300 complex had also completely returned to normal: N250-latency: 273.0 ms (less than 1sd); PFP300-latency: 348.0 ms (less than 1sd). This observation suggests that the analysis of P300 can help to detect and follow minor cognitive deficits in cases of acute hepatic encephalopathy. It further underscores the hepatic etiology as well as the potential reversibility of this type of encephalopathy.

Acute Disease↗

PubMed1991

[Dose-response relationships between blood alcohol concentrations and cognitive potentials (visual P300) in man].

20 healthy male subjects with a mean age of 24 +/- 2.7 years were intravenously administered a mean total dose of ethanol of 1.33 +/- 0.04 g ethanol/kg body weight using a perfusor device. The ethanol kinetic resulted in a "rising phase" of 90.2 +/- 0.9 min. in average. The PFP300 parameter in this phase of acute alcohol intoxication showed the following changes: Along with the increasing blood alcohol level the N250- and PFP300a-latencies of both the A- and B-potentials are progressively prolonged and the ascending PFP300-amplitudes are progressively reduced. The N250-latency of the B-potentials is shown to be the most sensitive parameter of the PFP300-complex already changing at a blood alcohol concentration (= b.a.c.) of 0.59 +/- 0.11% with a mean linear prolongation of 2.5 ms per 0.1 g ethanol/kg body weight. This prolongation reflects the increasing disability of the subjects to discriminate between task-relevant and task-irrelevant stimuli at b.c.a.-levels much below that being presently permitted for driving in the Federal Republic of Germany.

Adult↗

PubMed1988

The pattern flash elicited P300-complex (PF-P300): dynamics of its topographic scalp distribution in different states of visual attention.

PF-P300 has been recorded from 13 healthy male subjects (21-35 years) in two different conditions of visual attention (transient versus sustained attention) at 16 electrode locations (10/20-system) against linked mastoids. The PFP300 complexes were measured and mapped. Thus, we obtained the following: (1) N250 did not show any significant differences between both conditions. (2) PF-P300, however, showed significantly different (p less than or equal to .05) maps between both conditions, especially bilateral frontal and left occipital with the measured PFP300a-amplitudes being higher (p less than or equal to .01) under sustained attention. The PFP300a-latencies did not show such differences. (3) N400 showed similar (p less than or equal to .001) differences in its mean peak distribution, but its latencies were shorter (p less than or equal to .01 resp. .0001) at all recording sites (except Fz, Pz) in condition (2). (4) Further evaluation of the PFP300-complex under sustained attention by means of increment mapping and multichannel potential measurements showed that PFP300 first rises at Fz, Pz, then spreads over the left occipital region and culminates bilateral frontal and parieto-occipital. Interestingly, the latencies of N250 and PFP300a were shorter at O1 (p less than or equal to .01) than at O2. With the help of electrical brain mapping it is possible to study the dynamics of both the PFP300 scalp distribution between two distinct mental states and within one mental state.

Adult↗

PubMed1988

Colour-black pattern reversal visual evoked potentials (colour-black-PVEPs): neurobiological aspects and clinical applicability of a new method.

The new method of Colour-Black-PVEPs was applied to 67 healthy subjects with normal colour vision who were subdivided into age groups (= AG) I (N = 40: 18-30 years) and AG II (N = 27: 31-60 years): 1. For the N80-, P100- latencies and the N80P100-amplitudes of all Colour-Black-PVEPs we obtained age-, sex- and eye-matched normative data. 2. The female subjects of AG I showed shorter (p less than or equal to 0.05 resp. 0.002) P100-latencies and higher (p less than or equal to 0.02 resp. 0.0001) N80P100-amplitudes in the Colour-Black-PVEPs than the male subjects. In AG II, however, the Colour-Black-PVEPs did not show any more sex-differences for the P100-latencies, whereas the N80P100-amplitudes remained significantly higher for the females. 3. In the Colour-Black-PVEPs the N80- and P100-latencies did not reveal age-dependent changes. The N80P100-amplitudes, however, decreased with increasing age, but this was significant for the females only. 4. The head sizes, although decreasing with age, were in both age groups significant smaller for the females only. 4. The head sizes, although decreasing with age, were in both age groups significant smaller for the females. Therefore, head size alone could not fully explain the sex-differences in the Colour-Black-PVEPs and their age-dependent changes. 5. In both age groups, the N80--and P100-latencies increased significantly for both sexes from the Green-Black- and Red-Black-PVEPs to the Blue-Black-PVEPs. The N80P100-amplitudes decreased in the same sequence. This method may become a valuable tool in the investigation of neurophysiological and ophthalmoneurological aspects of human colour vision.

Adolescent↗

PubMed1988

The pattern flash elicited P300-complex (PF-P300): a new method for studying cognitive processes of the brain.

For neurological purposes we developed a new method for eliciting P300-waves: Using two different kinds of checkerboard stimuli that were randomly flashed on a TV screen we obtained, besides the well-known usable primary complex, prominent PF-P300-complexes consisting of a marked negative potential (= N250), the PFP300a and the N400 peaks. These components could be related to different cognitive processes such as floating versus selective sustained attention and stimulus evaluation. N250 especially was shown to be closely related to different degrees of difficulty in visual discrimination. Further, the PFP300 components are test-retest reliable and sex-independent. Since they have relative small interindividual variabilities, we consider the N250- and PFP300a-latencies especially as well as the ascending PFP300a-amplitudes to be appropriate parameters for investigating diseases with cognitive disorders objectively.

Brain↗

PubMed1988

[The visual P300 (pattern flash P300) in the physiologic aging process].

For studying the relationship between the PFP300 (Pattern Flash elicited P300) and age we investigated 73 healthy subjects - 34 males, 39 females - between 18 and 60 years of age by presenting randomly two different checkerboards A (16 X 16 caskets visual angle = 50') and B (64 X 64 caskets visual angle = 12.5') to them (A:B = 80:20). The subjects' task was to keep a running count in their heads of the infrequent B-stimuli only. The resulting A- and B-responses were derived from Oz to Fz (Cz was ground). The results were as follows: 1. Comparing the PFP300-parameters between age group I (N = 46, 18-30 years) and age group II (N = 27, 31-60 years) we found that in the elder group both the N250-latencies (in B-potentials) and the PFP300a-latencies (in A-potentials) are significantly prolonged (p less than or equal to 0.01). The ascending PFP300a-amplitudes, however, remain (still?) unchanged. 2. Regression analyses between the PFP300-parameters and age for the total group revealed significant relationships for both the N250- (r = 0.35, P less than or equal to 0.01) and PFP300a-latencies (r = 0.78, P less than or equal to 0.01) and PFP300a-latencies (r = 0.78, P less than or equal to 0.01). In contrast to this, we could only find a zero correlation for the ascending PFP300a-amplitudes. 3. The coefficient of the regression line was 0.71 ms/year for the N250-latency and 1.09 ms/year for the PFP300a-latency. These findings indicate that one has to build age-matched control groups for applying PFP300 to pathophysiological processes.

Adolescent↗

PubMed1988

[A new method of automatic cartography of EEG and evoked potentials. An addition to digital imaging diagnosis?].

We give an overview of historical development, methodology and clinical applications of a recently developed device for mapping multichannel EEG, spectral EEG and Evoked Potentials and displaying results as color-coded maps of electrical brain function within contours of a head. The option of mapping results of statistic analysis provides broad application to brain diseases, especially psychopathologic disorders of organic origin not detectable by any other imaging procedures.

Brain↗

PubMed1987

Pattern reversal visual evoked potentials (white-black- and colour-black-PVEPs) in the study of eye dominance.

We investigated the influence of eye dominance scaled by 6 tests on the parameters (N80, P100 latency and N80-P100 amplitude) of the white-black-, green-black-, red-black- and blue-black-pattern visual evoked potentials (PVEPs) of 40 healthy subjects (20 males and 20 females) with normal visual acuity. The P100 latency of the white-black PVEPs was, for both sexes, shorter (P less than or equal to 0.001) in the PVEPs of the dominant eyes. This P100 latency shortening could also be verified for both right dominant and left dominant eyes with no significant difference between them. A consistent relationship, however, between the different degrees of eye dominance and the P100 latency shortening could not be established. In contrast to the P100 latency findings the N80 latencies of the white-black-PVEPs and the N80-P100 amplitudes did not show any significant differences with respect to eye dominance. Furthermore, the colour-black PVEPs did not present any differences of latency and amplitude depending on eye dominance. Thus our results give further electrophysiological evidence for eye dominance as a lateralized CNS phenomenon that is not influenced by colour.

Adult↗

PubMed1984

[Malignant cerebellar infarct].

Three patients with cerebellar infarcts and secondary obstructive hydrocephalus (hydrocephalus occlusus) are described, the condition being due to the space-occupying action of the ischaemia and oedema zone with compression and displacement of the fourth ventricle and/or obstruction of the aqueduct. Possible brain stem compression and danger of cerebellar tonsillar herniation were present. From the acute deterioration of the clinical picture, particularly of the state of consciousness, as well as from the findings obtained via computed tomography showing a widening of the inner ventricular space, it was imperative to perform emergency pressure-relieving drainage surgery with ventriculo-atrial shunts in all the cases described. The first two patients could be discharged postoperatively with successful treatment, only slight neurological disturbances remaining. This leads to the conclusion that a (malignant) cerebral infarct should be treated as an emergency case, in a somewhat similar way as in cases of cerebellar haemorrhage or other space-occupying lesions in the posterior fossa of the skull. To recognize the life-threatening exacerbation, sufficient observation and supervision will be necessary. Rapid deterioration in consciousness should be considered a sign of increasing intracranial pressure progressing with the development of hydrocephalus internus occlusus. After neuroradiological diagnosis, especially after verification via computed tomography, this should be interpreted as an indication for immediate neurosurgical intervention. This is the only way to keep the mortality rate satisfactorily low. Dichotomy of cerebellar infarcts into a benign type with spontaneous decrease of symptoms and signs, and a malignant type with development of hydrocephalus internus and increased intracranial pressure, such as in the cases described here, is suggested.

Cerebellum↗

PubMed1981

[Stenoses of the cerebral arteries in pseudoxanthoma elasticum (author's transl)].

The Grönblad-Strandberg-Syndrome (Pseudoxanthoma elasticum) is a systemic disease of the elastic tissue, typical symptoms being lesion of skin and ocular fundi. The frequently appearing vascular changes, particularly of occlusive nature, are important for the patient's prognosis. Several clinical observations had led different authors to assume cerebrovascular involvement. Our neuroradiological findings support this opinion: In this report on a 45-year-old patient with acute hemisyndrome, we demonstrated, for the first time using computerized tomography, ischemic infarcts of both cerebral hemispheres. Cerebral angiography showed bilateral stenoses of the internal carotid arteries with further irregularities of the lumen of the intracranial arteries.

Carotid Artery Diseases↗

PubMed1976

[Simultaneous recording of visually evoked potentials (VEP) and registration of simple visual reaction times (RT) in the maximum range of ethanol influence (author's transl)].

The method of simultaneous recording of visual-evoked response (1 occipit-vertex) and simple reaction time to periodic foveal visual stimuli of 1/" per sec was applied to 16 normal individuals. On two successive days the conditions were kept constant except for an independent variable, i.e., ethanol with an average peak of 1.32%; the range of 0.1% below the peak being examined. The amplitude of the component N2-P3 (120-170 msec after the stimuli) was depressed in all individuals. The latencies of N2 and P3 were increased concurrently. The latency of P3, for example, was increased by 10.7% (P less than or equal 0.01) and that of the means of simultaneously recorded reaction time by 14.8% (P less than or equal 0.01). The amount of the increase, however, showed no significant correlation between the two when using Spearman's correlation coefficient and t-test.

Ethanol↗