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At least 973 records · Page 54Linked to original sources
PubMed1982

The localizing value of depth electroencephalography in 32 patients with refractory epilepsy.

Clinical seizure manifestations, physical examination, radiological studies, neuropsychological tests, and scalp and depth electroencephalographic (EEG) studies were done to localize seizure foci in 32 patients, 23 of whom have undergone surgery with more than one year of follow-up. Of 16 patients with unlocalized scalp EEGs, depth EEG detected a consistent focal seizure onset in 3. Of 15 patients with localized scalp EEGS, depth EEG revealed multiple foci in 3 and inaccurate localization of the focus by scalp EEG in 4. Therefore, localization by scalp EEG was inaccurate in 10 of 31 patients. When depth EEG revealed a consistent focal seizure onset and this localization was used to determine to surgical resection site, good to excellent results were obtained in 12 of 13 patients. When depth EEG revealed additional foci of seizure origin, surgical results were fair or poor in all patients. No other localizing criteria predicted depth EEG results or surgical success with such accuracy. Furthermore, some criteria, including neuropsychological tests and radiological abnormalities, were falsely localizing at times. Therefore, of the presently available localizing criteria, depth EEG appears to be the most accurate.

Adolescent↗
PubMed1990

Electroencephalography laboratory diagnosis of prolonged QT interval.

Patients with prolongation of the QT interval are at risk for significant neurological morbidity and mortality secondary to ventricular tachyarrhythmias. These patients frequently undergo electroencephalographic (EEG) examination to evaluate episodes of loss of consciousness, which may be associated with convulsions. Electrocardiogram recording as a part of the EEG is a simple and common practice, but analysis for possible QT prolongation is not routinely performed by electroencephalographers. This is, in part, due to the fact that while calculation of the corrected QT interval is straight forward, a calculator is generally required. A nomogram that is presented simplifies determination of the corrected QT interval, facilitating diagnosis of prolongation of the QT interval in the EEG laboratory.

Adult↗
PubMed1993

Characteristics of medial temporal lobe epilepsy: II. Interictal and ictal scalp electroencephalography, neuropsychological testing, neuroimaging, surgical results, and pathology.

Sixty-seven patients with temporal lobe epilepsy without circumscribed, potentially epileptogenic lesions, who were studied with intracranial electrodes and who became seizure free following temporal lobectomy were retrospectively evaluated with regard to preoperative scalp electroencephalographic (EEG) findings, neuropsychological test results, neuroimaging findings, results of surgery, and pathology of resected tissue. Interictal scalp EEG showed paroxysmal abnormalities during prolonged monitoring in 64 patients (96%). These were localized in the anterior temporal region in 60 (94%) of these 64 patients. Bilateral independent paroxysmal activity occurred in 42% of the patients and was preponderant over the side of seizure origin in half. Ictal EEG changes were rarely detected at the time of clinical seizure onset, but lateralized buildup of rhythmic seizure activity during the seizure occurred in 80% of patients. In 13%, the scalp EEG seizure buildup was, however, contralateral to the side of seizure origin as subsequently determined by depth EEG and curative surgery. Lateralized postictal slowing, when present, was a very reliable lateralizing finding. Neuropsychological testing provided lateralizing findings concordant with the side of seizure origin in 73% of patients. When neuropsychological testing produced discordant results or nonlateralizing findings, those patients were usually found to have right temporal seizure origin. Intracarotid amobarbital (Amytal) testing demonstrated absent or marginal memory functions on the side of seizure onset in 63% of patients, but 26 patients (37%) had bilaterally intact memory. In those patients who had magnetic resonance imaging, it was very sensitive in detecting subtle medial temporal abnormalities. These abnormalities were present in 23 of 28 magnetic resonance images, and corresponded with mesial temporal sclerosis on pathological examination in all but 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1995

Sleep electroencephalography and the clinical response to amitriptyline in patients with fibromyalgia.

OBJECTIVE: To determine the prevalence and clinical correlations of an anomaly consisting of electroencephalographic (EEG) waves within the alpha frequency band during non-rapid eye movement (NREM) sleep in patients with fibromyalgia, and to evaluate the alpha NREM sleep anomaly as a predictor of response to amitriptyline. METHODS: Twenty-two patients with fibromyalgia were studied in a 2-month, double-blind, crossover trial of amitriptyline (25 mg/day) versus placebo. Nocturnal EEGs were conducted on 2 consecutive nights at baseline and at the end of each 2-month treatment period. RESULTS: Six patients (27%) had a clinical response to amitriptyline, while none responded to placebo (P = 0.02). Treatment with amitriptyline or placebo did not result in any changes in the alpha ratings during NREM sleep. Only 8 patients (36%) exhibited the alpha NREM sleep anomaly at baseline. Those patients reported more sleep difficulty, but otherwise were clinically indistinguishable from those without this EEG sleep anomaly. Lower baseline alpha NREM sleep ratings were seen in responders to amitriptyline than in nonresponders, but these differences did not reach statistical significance. CONCLUSION: The alpha NREM sleep anomaly is present in only a small proportion of patients with fibromyalgia. It does not correlate with disease severity nor is it affected by treatment with amitriptyline. A larger sample size will be needed to adequately assess the value of this sleep anomaly in predicting the response to amitriptyline.

Adult↗
PubMed2005

Real-time display of artifact-free electroencephalography during functional magnetic resonance imaging and magnetic resonance spectroscopy in an animal model of epilepsy.

Simultaneous recording of electroencephalogram (EEG) and functional MRI (fMRI) or MR spectroscopy (MRS) can provide further insight into our understanding of the underlying mechanisms of neurologic disorders. Current technology for simultaneous EEG and MRI recording is limited by extensive postacquisition processing of the data. Real-time display of artifact-free EEG recording during fMRI/MRS studies is essential in studies that involve epilepsy to ensure that they address specific EEG features such as epileptic spikes or seizures. By optimizing the EEG recording equipment to maximize the common mode rejection ratio of its amplifiers, a unique EEG system was designed and tested that allowed real-time display of the artifact-free EEG during fMRI/MRS in an animal model of epilepsy. Spike recordings were optimized by suppression of the background EEG activity using fast-acting and easily controlled inhalational anesthesia. Artifact suppression efficiency of 70-100% was achieved following direct subtraction of referentially recorded filtered EEG tracings from active electrodes, which were located in close proximity to each other (over homologous occipital cortices) and a reference electrode. Two independent postacquisition processing tools, independent component analysis and direct subtraction of unfiltered digital EEG data in MATLAB, were used to verify the accuracy of real-time EEG display.

Algorithms↗
PubMed1994

Cordance: a new method for assessment of cerebral perfusion and metabolism using quantitative electroencephalography.

Increased slow-wave and decreased fast-wave activity on the electroencephalogram is common in brain dysfunction and may be caused by partial cortical deafferentation. No measure that is specific or sensitive for this deafferentation, however, has yet been reported. We studied a series of subjects with white-matter lesions undercutting the cortex and developed a method for analyzing electrical activity called "cordance" that has face validity as a measure of cortical deafferentation. Cordance is measured along a continuum of values: positive values denote "concordance," an indicator associated with normally functioning brain tissue; negative values denote "discordance," an indicator associated with undercutting lesions, low perfusion, and low metabolism. We present a series of subjects studied with magnetic resonance imaging, positron emission tomography, and single-photon emission computed tomography that demonstrate strong associations between cordance and other measures of brain structure and function.

Adult↗
PubMed1994

Automatic analysis of sleep using two parameters based on principal component analysis of electroencephalography spectral data.

A computer program for the analysis of a sleep electroencephalogram (EEG) is presented. The method relies on two steps. First, a spectral analysis is performed for signals recorded from one or more electrode locations. Then, two EEG parameters are obtained by storing the spectral activity in a multidimensional space, whose dimension is reduced using principal component analysis (PCA) techniques. The main advantage of these parameters is in describing the process of sleep on a continuous scale as a function of time. Validation of the method was performed with the data collected from 16 subjects (8 young volunteers and 8 elderly insomniacs). Results showed that the parameters correlate highly with the hypnograms established by conventional visual scoring. This signal parametrisation, however, offers more information regarding the time course of sleep, since small variations within individual sleep stages as well as smooth transitions between stages are assessed. Finally, the concurrent use of both parameters provides an original way of considering sleep as a dynamic process evolving cyclically in a single plane.

Adult↗
PubMed1986

Electroencephalography in minor head injury in children.

EEG and CT scans of 280 cases of minor head injury in children under 15 years of age were studied. Abnormality on initial EEG was shown in 42.5%. Those who lost consciousness had a higher incidence of abnormality than those who did not, and it was higher between 4 and 13 years of age. The sleep state has much influence on the finding. The patients should be awake or in a light sleep stage. The most frequent abnormality was slow waves, seen predominantly in the occipital regions, and which tended to disappear more easily than the paroxysmal ones. The EEGs became or remained normal in 95%, excluding incompletely followed-up cases. There was no case of post-traumatic epilepsy in our series, but 4 cases of post-traumatic early convulsions, in which the EEGs were variable. CT scan disclosed abnormality in 6%.

Adolescent↗