Computerized electroencephalography in the evaluation of early dementia

Mapping distributed sources of cortical rhythms in mild Alzheimer's disease. A multicentric EEG study

The study aimed at mapping (i) the distributed electroencephalographic (EEG) sources specific for mild Alzheimer's disease (AD) compared to vascular dementia (VaD) or normal elderly people (Nold) and (ii) the distributed EEG sources sensitive to the mild AD at different stages of severity. Resting EEG (10-20 electrode montage) was recorded from 48 mild AD, 20 VaD, and 38 Nold subjects. Both AD and VaD patients had 24-17 of mini mental state examination (MMSE). EEG rhythms were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). Cortical EEG sources were modeled by low resolution brain electromagnetic tomography (LORETA). Regarding issue i, there was a decline of central, parietal, temporal, and limbic alpha 1 (low alpha) sources specific for mild AD group with respect to Nold and VaD groups. Furthermore, occipital alpha 1 sources showed a strong decline in mild AD compared to VaD group. Finally, distributed theta sources were largely abnormal in VaD but not in mild AD group. Regarding issue ii, there was a lower power of occipital alpha 1 sources in mild AD subgroup having more severe disease. Compared to previous field studies, this was the first investigation that illustrated the power spectrum profiles at the level of cortical (macroregions) EEG sources in mild AD patients having different severity of the disease with respect to VaD and normal subjects. Future studies should evaluate the clinical usefulness of this approach in early differential diagnosis, disease staging, and therapy monitoring.

[Guidelines for recording/analyzing quantitative EEG and evoked potentials. Part II: Clinical aspects]

Digital EEG (DEEG) and quantitative EEG (QEEG) are recently developed tools present in many clinical situations. Besides showing didactic and research utility, they may also have a clinical role. Although a considerable amount of scientific literature has been published related to QEEG, many controversies still subsist regarding its clinical utilization. Clinical applications are: 1. DEEG is already an established substitute for conventional EEG, representing a clear technical advance. 2. Certain QEEG techniques are an established addition to DEEG for: 2a) screening for epileptic spikes or seizures in long-term recordings; 2b) Operation room and intensive care unit EEG monitoring. 3. Certain QEEG techniques are considered possible useful additions to DEEG: 3a) topographic voltage and dipole analysis in epilepsy evaluations; 3b) frequency analysis in cerebrovascular disease and dementia, mostly when other tests have been inconclusive. 4. QEEG remains investigational for clinical use in postconcussion syndrome, learning disability, attention disorders, schizophrenia, depression, alcoholism and drug abuse. EEG brain mapping and other QEEG techniques should be clinically used only by physicians highly skilled in clinical EEG interpretation and as an adjunct to traditional EEG work.

Status of quantitative EEG (QEEG) in clinical practice, 1994

Clinical quantitative EEG (qEEG) is a complex specialty that may include not only standard EEG but also digital ("paperless") EEG, topographic mapping, spectral analysis, spectral coherence, long latency and event related potentials (EP), significance probability mapping (SPM), dipole source localization methodology (DLM), and discriminant function analysis. There are three basic clinical uses: non-specific detection of organicity/encephalopathy, specific categorization of disease or clinical condition, and epileptic source localization. Extreme variations exist in the competency of laboratories practicing clinical qEEG; universally agreed upon standards of practice have not been established but there are a number of efforts to do so. As expected, the clinical value of qEEG to patients varies similarly. Criticisms of qEEG have now been answered: Color displays need not be deceptive. Statistical "capitalization upon chance" can be easily avoided. By training and with newer analytic procedures, artifacts can be recognized and often removed. Data based upon spectral analysis and EP can reliably classify clinical conditions thereby demonstrating a greater sensitivity to EEG/EP data than possible by conventional visual inspection. QEEG is clearly of clinical value when performed in concert with standard EEG and analyzed by clinicians with demonstrated competency in standard EEG followed by specialized training and demonstrated competency in qEEG. QEEG is not a simple substitute for conventional EEG and cannot be seen as a substitute for clinical competence. Although continuing to develop, qEEG technology has matured sufficiently and is now well established. Concerns regarding its clinical use have primarily resulted from its misapplication and misinterpretation stemming, largely, from inadequate personnel training and expertise.

Regional differences in brain electrical activity in dementia: use of spectral power and spectral ratio measures

The pathologic changes in dementia of the Alzheimer's type (DAT) commonly affect selected brain regions. The cortical areas affected in multi-infarct dementia (MID) are less predictable and may be secondary to subcortical gray or white matter damage that is widespread in MID. We compared several types of quantitative EEG power measures (absolute and relative power, and ratios of power) to determine their regional distribution, and their association with changes in cognitive status and age. We examined 49 subjects with clinically diagnosed mild-to-moderate DAT, 29 with mild-to-moderate MID, and 38 elderly controls (CON). We used discriminant analysis to identify, for each parameter type, the brain region and frequency band where the parameter best distinguished between groups of subjects. The parameters showed regional differences in distinguishing between DAT and MID subjects, and in their association with age and cognitive status. All parameters were useful for detecting differences between normal and demented subjects and correctly identified comparable proportions of subjects as having dementia. Subjects who were abnormal on several parameters were much more likely to have dementia. The additive effects of these parameters in correct classification suggest that they may be monitoring different physiologic processes. Combinations of several types of parameters may be more useful than individual parameters for distinguishing demented from non-demented subjects.

Prevalence and significance of electroencephalographic abnormalities in patients with suspected organic mental syndromes

OBJECTIVE

To determine the prevalence of electroencephalogram (EEG) abnormalities at different levels of cognitive impairment and to assess the possible diagnostic usefulness of the test.

DESIGN

Combined prospective assessment of subjects receiving EEGs and retrospective chart review of symptoms and medications.

SETTING

Academic geriatric psychiatry service.

PATIENTS

350 adults age 50 and above; 312 were patients being evaluated for possible organic mental syndrome and 38 were normal controls.

MEASUREMENTS

All subjects had EEGs and Mini-Mental State Examinations (MMSE) performed at the time of the EEG. EEGs were rated for the presence and type of abnormality, and subjects were stratified according to the severity of impairment. Charts were reviewed by a person blinded to EEG results to determine clinical diagnosis and medications received.

MAIN RESULTS

Abnormal EEGs were significantly more common among all patients (67%) in the study than among controls (11%), and the prevalence of abnormality increased with increasing impairment. Many demented patients with equivocal impairment (42%), and most with mild-to-moderate impairment (65%) had abnormal EEGs. An abnormal EEG was not indicative of dementia even when clear cognitive impairment was present, since patients with depression frequently also had abnormal EEG results.

CONCLUSIONS

These findings suggest that the EEG is a moderately sensitive but non-specific indicator of brain dysfunction in the elderly. The significance of abnormalities among patients with equivocal impairment should be more fully assessed by longitudinal follow-up to determine if greater cognitive impairment develops.

Diagnosis by electroencephalographic topography

In 5 patients, electroencephalographic (EEG) topography (Fourier analysis and topographic display of EEG data) demonstrated clinically significant acute brain lesions not seen by magnetic resonance imaging or computed tomography. EEG topography contributed to patient management more than standard EEG. Additional, carefully designed, prospective studies may indicate how frequently and in which settings EEG topography is a valuable diagnostic test.

Somatosensory evoked responses via electronic brain imaging (EBI)

This study of a series of 40 mildly head injured (concussed) patients suggests that different physiologic pathways underlying the tests done in a six-part resting EEG, and for the 11 evoked electrical potential shifts occurring in the cerebral terrain, are testable. Further work seems likely in order to ascertain which clinical signs and symptoms may be related to specific individual types of recorded electronic brain imaging (EBI) abnormality. Which of the 11 parameters studied, EEG, VER, AER, and SER, would be more or less likely to be abnormal in their individual patterns (as being deviant from normal controls) also remains to be defined. The relationship of these neurophysiologic abnormalities to certain postconcussive symptoms, i.e., headache, dizziness, blurred vision, etc., at this point in time remains to be evaluated more precisely. The authors suggest that further research is necessary in evaluating the clinical use of somatosensory evoked responses as an additional parameter in electronic brain imaging (EBI) technology.

Comparison of EEG background frequency analysis, psychologic test scores, short test of mental status, and quantitative SPECT in dementia

Fourteen patients who had cognitive dysfunction were studied with quantitative electroencephalography (EEG), single-photon emission computed tomography (SPECT), and several tests of intellectual and memory function, including the Wechsler Adult Intelligence Scale (WAIS), the Auditory Verbal Learning Test, and the Short Test of Mental Status, to determine whether EEG background frequency content correlates with degree of dementia and with regional uptake of radioisotope on SPECT. The factors from spectral analysis that correlated best with psychometric data were mean frequency in the 1.5- to 20-Hz range and percentage power in the 13- to 20-Hz band (positive correlation) or the 1.5- to 8-Hz band (negative correlation). The WAIS subtest scores that correlated most with the EEG data were performance IQ and perceptual organization. Correlations between percentage power and amplitude ratio in the EEG frequency bands and regional SPECT counts were found, but most were not statistically significant.

On the controversies about clinical use of EEG brain mapping

Quantitative EEG analysis, often called EEG Brain Mapping, consists of a large variety of separate techniques. Most of these techniques have demonstrated research uses, but few have been shown to have clinical applications that actually impact patient care. Substantial problems exist that can interfere with routine clinical applications. These include a variety of artifacts, confounding clinical problems, diversity of techniques and statistical issues. Existing medical literature suggests several areas where there are clinical uses at this time. EEG Brain Mapping can be used as a testing technique to determine abnormality and perhaps as a monitoring tool, too. It should be viewed as complementary to neuroimaging techniques, rather than a competitor. Those who introduce costly new technology bear the burden of proof for demonstrating its usefulness and cost-effectiveness. Evaluation of new tests should be based on several principles outlined here. EEG Brain Mapping, when used for clinical purposes, should be read together with the accompanying traditional polygraph EEG record. Reproducibility of results should be demonstrated, and artifacts, normal variants and other problems must be identified or avoided. The reader must recognize that features noted on statistical tests do not necessarily imply that pathology exists. Reporting results and clinical implications should be done carefully, thoroughly and with appropriate caution. Results are often quite nonspecific. The user must have skills, knowledge and abilities for reading polygraph EEG as well as additional experience and knowledge about quantitative EEG techniques and problems. Experts must remain careful and responsible about introducing EEG Brain Mapping into routine clinical practice.