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PubMed2005

[Hans Berger (1873-1941)--the history of electroencephalography].

The discovery of electroencephalography (EEG) in 1929 by the German psychiatrist Hans Berger was a historical breakthrough providing a new neurologic and psychiatric diagnostic tool at the time, especially considering the lack of all those now available in daily practice (EP, CT, MRI, DSA, etc.) whithout which the making of neurologic diagnosis and planning neurosurgical operative procedures would now be unconceivable. There are no recent reports on the topic in the Croatian medical literature. The methods used in the study included search through previous reports, bibliographic notes, Internet sources, and analysis of continuous scientific attempts made through centuries to discover the real nature and meaning of electrical activity. Galvani's accidental discovery of "biological electricity" led to Volta's discovery of the battery (voltaic pile). Using it, Rolando was the first to stimulate cerebral surface. Thus, enabling Fritsch and Hitzig and Ferrier to develop the idea of cerebral localization (Jackson, Gowers, Gotch and Horsley). It was understandable that brain electrical stimulation produces contralateral motor response, but it was unknown whether there was a spontaneous (intrinsic) brain electrical current that could be recorded. Caton was the first to report on the "current in the brain gray substances onto open brain. Based on Caton's discovery and of those of Beck, Danilevsky, Prawdicz-Neminsky and others, Berger made the first EEG (electrocorticogram) recording on July 6, 1924, during a neurosurgical operation on a 17-year-old boy, performed by the neurosurgeon Nikolai Guleke. He reported on the topic in 1929, using the terms alpha and beta waves. The "spike and waves" (Spitzenwellen) were described shortly thereafter by the American group of EEG pioneers (H. and P. Davies, F. and E. Gibbs, Lenox and Jasper), although Berger had also observed them but considered them artifacts. The discovery of electroencephalography was a milestone for the advancement of neuroscience and of neurologic and neurosurgical everyday practice, especially for patients with seizures. The real nature of the disease and its management (anticonvulsants, excision of brain scars, tumors, etc.) were unkonown at that time. Berger's persistent, hardworking and steady personal style overcame all technical and other obstacles during the experiments. Unfortunately, he gained neither acceptance nor recognition, among his fellow contemporaries from abroad. Political turmoils at the dawn of World War II, in the country of Nazi's ideology and finally the outbreak of war, along with the complete ban of any further work on EEG after his forced retirement, led him to an uneasy professional and personal end. In the era when lumbar puncture, pneumoencephalography and ventriculography were the only diagnostic tools to detect and localize "sick sites" in the brain, EEG revolutionized daily neurologic and neurosurgic procedures, and bridged a time period of about 40 years (1930-1970) until the advent of computer tomography. Nowadays its importance is not as great as it was before, but it still has its place in the diagnostic work-up of seizures, brain tumors, degenerative brain changes, and other diseases.

Electroencephalography↗
PubMedDate not supplied

[Video-electroencephalography prolonged monitoring in patients with ambulatory diagnosis of medically refractory temporal lobe epilepsy: application of fuzzy logic's model].

INTRODUCTION: The video-electroencephalography (video-EEG) prolonged monitoring is an important auxiliary diagnostic instrument in epilepsy, and provides valuable information to classify the type of crisis and epileptic syndromes and to localize the epileptogenic zone. The fuzzy logic gives an efficient and intelligent analysis method, able to make inferences over ambiguous systems, and has been increasing used in several areas. AIMS: To correlate clinical and electroencephalographic data obtained with video-EEG of patients with clinical and interictal electroencephalography criteria of medically refractory temporal lobe epilepsy (TLE) and to make inferences of diagnosis precision with the application of the Fuzzy Hierarchy COPPE/Cosenza Model; to investigate the frequency in which the clinical, syndromic and topographic diagnosis can be modified in these patients; to evaluate the usefulness and applicability of fuzzy logic on the analysis of this type of study. PATIENTS AND METHODS: Transversal, prospective study, that included 22 adult outpatients with ambulatory diagnosis of medically refractory TLE, submitted to video-EEG monitoring that varied from 48 hours to 10 days. The grade of diagnosis precision was infered by fuzzy logic. RESULTS: The clinical diagnosis of epilepsy was modified in two (9%) patients, the syndromic in six (27.2%) and the topographic in 16 (72.7%). The fuzzy indicators of ambulatory diagnostic precision were: 0.91 to clinical diagnosis; 0.74 to syndromic diagnosis and 0.36 to topographic diagnosis, considering 1 the maximal precision diagnostic value (attributed to the video-EEG results). CONCLUSIONS: The video-EEG prolonged monitoring established the clinical, syndromic and topographic correct diagnosis in these patients; the fuzzy logic best defined a mathematical value of the correspondence between ambulatorial diagnosis of TLE and the video-EEG prolonged monitoring.

Adult↗
PubMed1991

Quantitative electroencephalography in dogs anesthetized with 2.0% end-tidal concentration of isoflurane anesthesia.

Quantitative electroencephalography was assessed in dogs under controlled, 2% end-tidal isoflurane anesthetic conditions, and each variable at each electrode site was tested for normal distribution. With the quantitative electroencephalographic system used, 16 values for each of 21 electrode sites were evaluated. Absolute power ratios also were evaluated. The methods for quantitative electroencephalographic recording and analysis appear to be readily adaptable to the dog. Most of the data do not conform to a normal distribution. Therefore, distribution-free nonparametric statistics should be used when looking for differences under experimental or clinical conditions. Quantitative electroencephalography appears to be a sensitive noninvasive method that could be used to evaluate brain function under anesthetic, clinical, and experimental settings.

Acid-Base Equilibrium↗
PubMedDate not supplied

[Neurophysiological diagnosis of AIDS dementia complex: importance of electroencephalography].

This study reports the results obtained by an Electroencephalographic screening of 450 HIV-seropositive patients, belonging to different stages of infection. The major bioelectrical changes of cerebral activity were evident in AIDS group (87.2%) and in ARC group (64.5%), whereas mild abnormalities were present in LAS group (38.8%) and in asymptomatic infection (19.2%), often without any evidence of neuropsychological impairment. Therefore, we emphasize the usefulness and the sensibility of Electroencephalography and, in particular, of Electroencephalography coupled with Computerized Spectral Analysis with the aim of identifying the subclinical stages of AIDS Dementia Complex.

AIDS Dementia Complex↗
PubMed1971

[Electrical picture of the brain under increased respiration in children. Studies on the structure of hyperventilation and its value as a provocation method in clinical electroencephalography in a model of multivariate analysis using electronic data processing].

In clinical electroencephalography, hyperventilation is the most used method of activation. However, knowledge of the conditions of hyperventilation with regard to their effects on the EEG is so far rather undifferentiated. For this reason the effects of hyperventilation in 1109 children are examined in this paper based on clinical and electroencephalographic parameters of a data configuration with a large number of criteria and the results obtained are calculated with the aid of electronic data processing. The statistical methods of examination were frequency and significance investigations by chi 2 tests, multifactorial analysis of variance, multiple regression analysis of influencing quantities, and determination of the reliability of the quantitative method of evaluation. New knowledge on group-statistical validity was obtained with this multivariant analysis and it was thus possible to extend the value of hyperventilation as a method of provocation in clinical electroencephalography. The increase in knowledge is based in particular on the facts that the hyperventilation effects are practically independent of sex, they do not require the consideration of certain age related development modalities of the EEG, they are diagnostically significant as regards unspecific changes of the bioelectrical activity, and they make a differentiated consideration with reference to their strength necessary, which results in 4 types of forms of changing the EEG spectrum. In addition to this, a recurrence of EEG changes was observed after the HV effect proper had faded, and the term "Reprise" is suggested for this and its clinico-encephalographic importance discussed. It was also found that occipital maxima dominate and that changes in frequency and amplitude require separate consideration. The influence of respiratory rate, tidal volume minute volume, alveolar CO2 tension, blood sugar and body weight on the strength of the effect of hyperventilation is not very significant. Mean controlled hyperventilation has proved useful to standardise arbitrary hyperventilation; an improvement could be achieved at the most by norming the respiratory rate. It was possible to prove that the applied method of non-mechanical quantitative EEG analyses had a high degree of accuracy and is consequently suitable for scientific investigations.

Adolescent↗
PubMed1998

Subclinical cerebral complications after coronary artery bypass grafting: prospective analysis with magnetic resonance imaging, quantitative electroencephalography, and neuropsychological assessment.

OBJECTIVE: To analyze the frequency and severity of subclinical cerebral complications associated with coronary artery bypass grafting (CABG). DESIGN: A prospective controlled study using preoperative and postoperative magnetic resonance imaging (MRI) of the brain, quantitative electroencephalography (QEEG), and detailed neuropsychological and neurologic examinations as potentially sensitive indicators of subclinical cerebral injury associated with CABG. SETTING: Multimodality evaluation in a tertiary care unit (Kuopio University Hospital, Kuopio, Finland). PATIENTS: Thirty-eight patients undergoing elective CABG and 20 control patients undergoing other major vascular surgery, mostly operations on the abdominal aorta. MAIN OUTCOME MEASURES: Coronary artery bypass grafting-associated cerebral complications assessed preoperatively and postoperatively by brain MRI, QEEG, detailed neurologic examination, and a neuropsychological test battery that evaluates cognitive functions in major areas known to be vulnerable to organic impairment (learning and memory, attention, flexible mental processing, and psychomotor speed). RESULTS: There were no major neurologic complications. A mild hemisyndrome developed in 1 patient who underwent CABG and in 1 control patient. Overall, there was no decline in mean cognitive performance 3 months after surgery. Electroencephalographic slowing of 0.5 Hz or more in at least 2 channels occurred in 11 patients who underwent CABG and in 1 control patient (P=.03). The postoperative brain MRI scan revealed new small ischemic lesions in 8 patients (21%) in the CABG group but in none of the control group (P=.03). These new cerebral MRI lesions did not explain deterioration in neuropsychological test performance or the QEEG slowing. CONCLUSIONS: Coronary artery bypass grafting causes more QEEG alterations and small ischemic cerebral lesions that are detectable by MRI than does other major vascular surgery. The effect is mainly subclinical, because no statistically significant deterioration in mean neuropsychological test performance was detected.

Aged↗
PubMed1998

Quantitative spectral electroencephalography in predicting survival in patients with early Alzheimer disease.

OBJECTIVE: To determine whether measures of quantitative spectral electroencephalography (EEG) can predict survival in patients with early Alzheimer disease. DESIGN: Prospective cohort study; median duration of follow-up was 4.4 years in survivors and 2.6 years in nonsurvivors. Cox proportional hazards models, with adjustment for age and sex were used to estimate relationships between EEG measures and survival. Log relative percentage values of EEG bands were used as predictors. SETTING: Outpatient university memory clinic. PARTICIPANTS: One hundred one consecutively referred patients with early probable Alzheimer disease according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria were studied with EEG at the time of diagnosis. The mean age of the patients was 79.2 years, which was higher than in previous EEG studies. MAIN OUTCOME MEASURE: Mortality. RESULTS: Fifty-one patients (50.5%) died during follow-up, with a median survival time in all patients of 4.1 years. The following EEG variables were significantly associated with increased risk of mortality: from parieto-occipital leads, higher theta (hazard ratio, 2.05; 95% confidence interval, 1.15-3.66; P<.05), lower alpha (hazard ratio, 0.43; 95% confidence interval, 0.25-0.76; P<.01), and lower beta (hazard ratio, 0.38; 95% confidence interval, 0.22-0.68; P<.001) activity; and from frontocentral leads, higher theta activity (hazard ratio, 2.07; 95% confidence interval, 1.17-3.66; P<.05). Stepwise Cox regression analysis showed that loss of parieto-occipital beta (P<.01) and alpha (P<.05) power were independent and significant predictors of mortality. Both beta (12.6-35.4 Hz) and alpha (7.5-12.5 Hz) activity remained significantly associated with mortality after adjustment for education, dementia severity, symptom duration, level of cognitive function, presence of extrapyramidal symptoms or hallucinations, presence of vascular risk factors, and presence of leukoaraiosis or local cortical atrophy. CONCLUSIONS: Decreases of beta and alpha activity on quantitative spectral EEG are independent predictors of mortality in patients with early Alzheimer disease. In the clinical context, the use of EEG technology for prediction of survival in individual patients remains to be determined.

Aged↗
PubMed1989

Electroencephalography (EEG) in the differential diagnosis of dementia.

Recent technical advances in neurodiagnostic procedures have improved significantly our knowledge of the pathophysiology of a number of disease processes and how they relate to behavioral manifestation. This paper focuses on advances in electroencephalography (EEG) and the implications that this growing body of research has for the diagnosis of suspected brain disorders in older patients.

Aged↗
PubMed1981

Depth electroencephalography in selection of refractory epilepsy for surgery.

Depth electroencephalography (EEG) is sometimes used to evaluate medically refractory epileptic patients for surgical treatment. Surgical excision of well-defined epileptogenic foci has been shown repeatedly to cause a substantial reduction of seizure frequency in 60 to 80% of these patients; however, because surgical success is no better at centers that employ depth EEG in patient evaluation, the procedure remains controversial. Review of the available literature shows that depth EEG results reported to date, when compared to scalp EEG results in 178 patients, could have enabled selection of 36% more patients for surgery by defining otherwise unidentifiable single epileptogenic foci. Furthermore, depth EEG could have prevented surgery in another 18% by demonstrating different or additional epileptogenic foci in patients otherwise thought to have a single discharging focus amenable to resection. Thus depth EEG had the potential to alter the surgical decision in more than 50% of patients reported. Centers that employ depth EEG may evaluate a different population of patients, which could account for their lack of increased surgical success.

Electrodes, Implanted↗
PubMed1989

Hereditary long Q-T syndrome presenting as epilepsy: electroencephalography laboratory diagnosis.

Patients with hereditary Q-T interval prolongation can present with seizures, syncope, and sudden death. In 2 siblings with autosomal dominant familial long Q-T syndrome, electroencephalographic examinations performed 6 and 2 years before diagnosis included electrocardiographic tracings documenting the cardiac abnormality. A timely diagnosis of this condition may have prevented the death of 1 of these patients. Measurement of the corrected Q-T interval on electrocardiographic tracings obtained in the electroencephalography laboratory should be considered in selected patients.

Adolescent↗
PubMed1991

Comparison of bitemporal and unitemporal epilepsy defined by depth electroencephalography.

Of 166 consecutive patients studied with depth electroencephalography (EEG), 87 had seizures arising from one temporal lobe and 23 had seizures arising independently from each temporal lobe. We retrospectively reviewed and compared those patients with unitemporal and those with bitemporal seizures. There was no statistically significant differences between the two groups in terms of age at onset of seizures, duration of epilepsy, localization of scalp EEG abnormalities, surgical results, or pathological findings. The bitemporal group, however, had significantly fewer patients with a history of febrile seizures (p less than 0.025). Two patients with bitemporal seizures were later found to have extratemporal lesions, and one an extrahippocampal temporal lesion, on magnetic resonance scans; one patient's extratemporal lesion was resected and all habitual seizures stopped. These findings suggest that a single pathophysiological process accounts for unitemporal and some bitemporal epilepsy, but that independent onset of seizures from each temporal lobe detected by depth EEG may also indicate extratemporal foci.

Adolescent↗
PubMed1991

Temporal lobectomy in patients with bitemporal epilepsy defined by depth electroencephalography.

Patient selection for temporal lobectomy was reviewed for 23 patients with seizures that arose independently from each temporal lobe as detected by depth electroencephalography (EEG). Although neuropsychological testing, interictal EEG findings, imaging studies, and subclinical seizures were also considered, all patients offered temporal lobectomy had (1) at least 50% of the clinical seizures originating from the lobe to be resected, (2) adequate contralateral memory on testing with amobarbital, and (3) no clear evidence of an extratemporal focus. Eleven patients underwent temporal lobectomy. Pathological findings were considered positive in all nine specimens reviewed. Nine patients had no seizures, one had greater than 75% reduction in seizure frequency, and 1 had 50 to 75% reduction. Pathological features and clinical outcome were similar in the 6 patients with fewer than 80% and the 5 patients with at least 80% of seizures originating from the resected lobe. Thus, having fewer than 80% of seizures originate from one temporal lobe should not be an absolute contraindication for temporal lobectomy.

Adolescent↗
PubMed1992

Quantitative electroencephalography. A new approach to the diagnosis of cerebral dysfunction in systemic lupus erythematosus.

OBJECTIVE: Neuropsychiatric manifestations are common in patients with systemic lupus erythematosus (SLE), but accurate diagnosis is often difficult. We conducted a prospective study to determine the utility of neurometric quantitative electroencephalography (QEEG) as an indicator of cerebral dysfunction in SLE patients. METHODS: Fifty-two SLE patients were divided into 4 groups based on the results of neuropsychiatric evaluations. These included patients with objective evidence of neuropsychiatric SLE (NPSLE), patients with neuropsychiatric symptoms, patients with no evidence of NPSLE, and patients with a prior history of NPSLE: All QEEG findings were compared with data in an age-regressed normative database and with findings in an independent sample of normal subjects. RESULTS: QEEG sensitivity was 87%, and specificity was 75%. QEEG results were abnormal in 74% of the SLE patients with neuropsychiatric symptoms and in 28% of the patients with no evidence of active NPSLE: QEEG profiles varied as a function of the severity and type of neuropsychiatric manifestation present. Within this patient population, QEEG was more sensitive than magnetic resonance imaging, computed tomography scanning, or conventional EEG. CONCLUSION: Neurometric QEEG may be a sensitive indicator of cerebral dysfunction in patients with NPSLE and can differentiate patients with diverse neuropsychiatric manifestations. When combined with a careful clinical history and evaluation, QEEG provides information that may be useful for the early detection of NPSLE and for serial evaluation of disease activity and treatment efficacy.

Adult↗
PubMed2005

Electroencephalography in the assessment of neuropsychiatric manifestations in antiphospholipid syndrome and systemic lupus erythematosus.

OBJECTIVE: To describe the prevalence and clinical associations of abnormalities on electroencephalography (EEG) in patients with antiphospholipid syndrome (APS) and/or systemic lupus erythematosus (SLE) who have neuropsychiatric symptoms. METHODS: The study group comprised 57 patients (age </=50 years) with manifestations of neuropsychiatric illness. Patients with stroke, epilepsy, or other encephalopathies were excluded. Fourteen patients had APS, 24 patients were positive for antiphospholipid antibodies (aPL), and 19 patients had SLE without aPL. All patients underwent EEG and brain magnetic resonance imaging (MRI) while they were awake. RESULTS: Abnormal EEG findings (showing mainly bitemporal slow activity) were recorded in 37 of 57 patients (65%). Abnormal EEG findings were observed in all patients with APS and in 17 of 24 aPL-positive patients (71%), compared with 6 of 19 patients with SLE (32%) (P < 0.001 and P < 0.05, respectively). There was an association between abnormal EEG findings and the frequency of aPL positivity (at least 2 positive results) (P = 0.002). Three EEG recordings showed potentially epileptiform activity. Results of brain MRI were abnormal in 18 (31.6%) of 57 patients: 8 in the APS group (57.1%), 7 in the aPL-positive group (29.2%), and 3 in the SLE group (15.8%). None of the patients with normal EEG findings had abnormal MRI results. Thus, brain MRI findings were normal in the majority of patients. Patients with abnormal EEG results were more likely to report memory problems (P < 0.001). CONCLUSION: Our findings suggest that EEG abnormalities are common and correlate with the presence of aPL even in the absence of brain abnormalities on MRI. EEG should be considered in aPL-positive patients with neuropsychiatric symptoms, because use of antiaggregants or anticoagulation may need to be considered.

Adult↗
PubMed1987

Multimodality evoked potentials and electroencephalography in severe coma cases. Clinical experiences in a neurosurgical intensive care unit.

In a neurosurgical intensive care unit 26 patients with unconsciousness and unresponsiveness were investigated by means of multimodality evoked potentials and electroencephalography in order to obtain information on the functional state of the nervous system. Multimodality evoked potential techniques allowed us to differentiate patients with EEG alterations due to drug treatment from those without therapy. The functional state and prognosis can be better evaluated by means of evoked potential techniques. Patients with raised intracranial pressure seem to undergo some characteristic alterations in FEP and far field potential derivations.

Adolescent↗
PubMed1998

Utility of multimodal evoked potential study and electroencephalography in mitochondrial encephalomyopathy.

We performed electroencephalography (EEG) and multimodal evoked potential (EP) studies in 16 patients with various forms of mitochondrial encephalomyopathy (ME). The electrophysiological investigations revealed signs of involvement of the peripheral and central nervous system (CNS) in 14 patients, with a high incidence of visual-EP (VEP) alterations, indicative of visual pathway vulnerability in mitochondrial diseases. No specific pattern of abnormalities emerged and, in particular, clinical and laboratory findings did not correlate with each other. EP (particularly VEP and electroretinogram) investigations should be part of the diagnostic work-up of patients with mitochondrial disorders in order to better characterize the clinical picture, disclose involvement of specific sensory systems of the CNS, and assess patients with atypical clinical presentations.

Adult↗
PubMed1988

Phase space electroencephalography (EEG): a new mode of intraoperative EEG analysis.

Intraoperative monitoring of electroencephalography (EEG) data can help assess brain integrity and/or depth of anesthesia. We demonstrate a computer generated technique which provides a visually robust display of EEG data plotted as 'phase space trajectories' and a mathematically derived parameter ('dimensionality') which may correlate with depth of anesthesia. Application of nonlinear mathematical analysis, used to describe complex dynamical systems, can characterize 'phase space' EEG patterns by identifying attractors (geometrical patterns in phase space corresponding to specific ordered EEG data subjects) and by quantifying the degree of order and chaos (calculation of dimensionality). Dimensionality calculations describe the degree of complexity in a signal and may generate a clinically useful univariate EEG descriptor of anesthetic depth. In this paper we describe and demonstrate phase space trajectories generated for sine waves, mixtures of sine waves, and white noise (random chaotic events). We also present EEG phase space trajectories and dimensionality calculations from a patient undergoing surgery and general anesthesia in 3 recognizable states: awake, anesthetized, and burst suppression. Phase space trajectories of the three states are visually distinguishable, and dimensionality calculations indicate that EEG progresses from 'chaos' (awake) to progressively more 'ordered' attractors (anesthetized and burst suppression).

Electroencephalography↗
PubMed1997

Combined electroencephalography and measurements of transcranial blood flow velocity during orthostatic testing--a new approach to assess syncope of unknown origin?

Differential diagnosis of syncope and seizures frequently imposes a major problem, particularly if interictal examinations are normal. We performed orthostatic testing combined with surface electroencephalography (EEG) and non-invasive measurements of cerebral blood flow velocity. Ten healthy controls, ten patients with confirmed diagnosis of epilepsy and 25 patients with history of syncope of unknown origin were examined. The following parameters were evaluated continuously and simultaneously during orthostatic challenge: computerized EEG with synchronous video-monitoring, transcranial Doppler sonography (TCD), heart rate and blood pressure. Isolated cerebrovascular dysregulation (i.e. a drop in cerebral perfusion despite the absence of a significant drop in peripheral blood pressure) occurred in 2/10 controls, 3/10 patients with epilepsy and 11/25 patients with syncope of unknown origin. The combined EEG and TCD measurements represent a new approach to the work-up of patients with otherwise unexplained syncope, helping us to understand the interdependence of neuronal activity and peripheral/cerebrovascular autoregulation under postural stress.

Adolescent↗