Correlation between diffuse EEG abnormalities and cerebral atrophy in senile dementia

Qualitative electroencephalogram and its predictors in the diagnosis of stroke

Introduction

Stroke is a typical medical emergency that carries significant disability and morbidity. The diagnosis of stroke relies predominantly on the use of neuroimaging. Accurate diagnosis is pertinent for management decisions of thrombolysis and/or thrombectomy. Early identification of stroke using electroencephalogram (EEG) in the clinical assessment of stroke has been underutilized. This study was conducted to determine the relevance of EEG and its predictors with the clinical and stroke features.

Methods

A cross-sectional study was carried out where routine EEG assessment was performed in 206 consecutive acute stroke patients without seizures. The demographic data and clinical stroke assessment were collated using the National Institutes of Health Stroke Scale (NIHSS) score with neuroimaging. Associations between EEG abnormalities and clinical features, stroke characteristics, and NIHSS scores were evaluated.

Results

The mean age of the study population was 64.32 ± 12 years old, with 57.28% consisting of men. The median NIHSS score on admission was 6 (IQR 3-13). EEG was abnormal in more than half of the patients (106, 51.5%), which consisted of focal slowing (58, 28.2%) followed by generalized slowing (39, 18.9%) and epileptiform changes (9, 4.4%). NIHSS score was significantly associated with focal slowing (13 vs. 5, p < 0.05). Type of stroke and imaging characteristics were significantly associated with EEG abnormalities (p < 0.05). For every increment in NIHSS score, there are 1.08 times likely for focal slowing (OR 1.089; 95% CI 1.033, 1.147, p = 0.002). Anterior circulation stroke has 3.6 times more likely to have abnormal EEG (OR 3.628; 95% CI 1.615, 8.150, p = 0.002) and 4.55 times higher to exhibit focal slowing (OR 4.554; 95% CI 1.922, 10.789, p = 0.01).

Conclusion

The type of stroke and imaging characteristics are associated with EEG abnormalities. Predictors of focal EEG slowing are NIHSS score and anterior circulation stroke. The study emphasized that EEG is a simple yet feasible investigational tool, and further plans for advancing stroke evaluation should consider the inclusion of this functional modality.

Clinical correlative evaluation of an iterative method for reconstruction of brain SPECT images

BACKGROUND

Brain SPECT and PET investigations have showed discrepancies in Alzheimer's disease (AD) when considering data deriving from deeply located structures, such as the mesial temporal lobe. These discrepancies could be due to a variety of factors, including substantial differences in gamma-cameras and underlying technology. Mesial temporal structures are deeply located within the brain and the commonly used Filtered Back-Projection (FBP) technique does not fully take into account either the physical parameters of gamma-cameras or geometry of collimators. In order to overcome these limitations, alternative reconstruction methods have been proposed, such as the iterative method of the Conjugate Gradients with modified matrix (CG). However, the clinical applications of these methods have so far been only anecdotal. The present study was planned to compare perfusional SPECT data as derived from the conventional FBP method and from the iterative CG method, which takes into account the geometrical and physical characteristics of the gamma-camera, by a correlative approach with neuropsychology.

METHODS

Correlations were compared between perfusion of the hippocampal region, as achieved by both the FBP and the CG reconstruction methods, and a short-memory test (Selective Reminding Test, SRT), specifically addressing one of its function. A brain-dedicated camera (CERASPECT) was used for SPECT studies with 99mTc-hexamethylpropylene-amine-oxime in 23 consecutive patients (mean age: 74.2 +/- 6.5) with mild (Mini-Mental Status Examination score > or =15, mean 20.3 +/- 3), probable AD. Counts from a hippocampal region in each hemisphere were referred to the average thalamic counts.

RESULTS

Hippocampal perfusion significantly correlated with the MMSE score with similar statistical significance (p < 0.01) between the two reconstruction methods. Correlation between hippocampal perfusion and the SRT score was better with the CG method (r = 0.50 for both hemispheres, p < 0.01) than with the FBP method (r = 0.37 and 0.43, respectively for the right and left hemisphere, p < 0.05 and p < 0.02). The bootstrap procedure showed that such correlation indexes were statistically different both in the right (p < 0.01) and in the left (p < 0.05) hemisphere.

CONCLUSION

These results are interpreted as a better performance of the CG reconstruction method in correctly detecting counts from hippocampal ROI. By using the same gamma-camera or collimator, alternative methods for brain SPECT reconstruction may improve quality of data and then help SPECT diagnostic accuracy.

Timing of disease progression by quantitative EEG in Alzheimer' s patients

This prospective study was planned to assess whether quantitative EEG (qEEG) can give an estimate of the timing of achievement of three endpoints (loss of activities of daily living, incontinence, and death) in 72 consecutive patients (53 females, 19 males; mean age, 70.8) affected with probable Alzheimer's disease, as defined according to the NINCDS-ADRDA criteria. Power-weighted, log-transformed relative values of the four conventional EEG bands were considered in a central-posterior temporal region for each hemisphere. The hypothesis was tested by the lifereg procedure of the Statistical Analysis System package (first significance level accepted, P < or = 0.01). Because patients were in different stages of the disease, the statistical analysis was performed in the entire group as well as in the subgroup of 41 patients (mean age, 69.6) with mild dementia (scoring 3 or 4 on the global deterioration scale). In the whole group, the loss of activities of daily living was predicted by delta power in either side (P = 0.01), incontinence was predicted by alpha power in the right side (P < 0.01), whereas the statistical significance was not reached for death (P < 0.05). In the subgroup of mild demented patients, the loss of activities of daily living was predicted by delta power in the left side (P = 0.01), incontinence by both delta (P < 0.01) and alpha (P < 0.001) power in the right side, and death was not significantly predicted (P = 0.08). Quantitative EEG is a low-cost, discomfort-free technique which may be used to obtain information on the timing of disease evolution. The results showed in mild Alzheimer's disease appear especially interesting to attempt a prediction of the future time course of the disease from its beginning.

Quantitative EEG analysis in early onset Alzheimer's disease: correlations with severity, clinical characteristics, visual EEG and CCT

We report EEG findings in 15 presenile Alzheimer patients (probable Alzheimer's disease according to NINCDS-ADRDA criteria) in relation to clinical characteristics. The quantitative EEG was analysed in terms of absolute band power while accounting for EOG and EMG artifacts, respectively. The degree of dementia is strongly reflected by an increase of power in the delta frequency band, accentuated on the left hemisphere, as well as decrease of alpha activity. Longer duration of disease is associated with a decrease of power in the alpha frequency band, earlier age at onset with an additional increase of power in the theta frequency band. Visual EEG evaluation correlates highly with the degree of dementia, in contrast to visually assessed CCT.

EEG in the differential diagnosis between Alzheimer's disease and vascular dementia

Demented patients with Alzheimer's disease (AD) (n = 67), multi-infarct dementia (MID) (n = 77) and probable vascular dementia (PVD) (n = 45) were studied with electroencephalography (EEG). All patients underwent a routine EEG examination and quantitative EEG was recorded from 14 patients with AD, 20 with MID, and 12 with PVD. The patient groups did not differ in regard to sex, age, education, or degree of dementia. Diffuse abnormality of EEG increased in AD, while driving response to photic stimulation and the mean frequency of background activity decreased in all groups with increasing degree of dementia. In quantitative EEG, the percentage of alpha power decreased and those of theta and delta power increased relative to the degree of dementia. Focal abnormalities, and irritative (spikes and/or sharp waves) and slow wave paroxysms were more common in MID than in AD. Patients with different types of dementia did not differ significantly in regard to diffuse abnormality, occurrence of driving response, mean background frequency, or parameters of quantitative EEG. The mean frequency of background activity and the degree of diffuse abnormality correlated with central and cortical atrophy, white matter low attenuation seen on computed tomography, and with neuropsychological findings.

The EEG in the normal elderly: a contribution to the interpretation of aging and dementia

Forty-seven normal elderly, 16 normal subjects ranging from 40 to 60 years of age and 14 patients affected by primary dementia are studied. The EEG is recorded from different brain areas and analysed by FFT algorithm. Main results are: There is persistence of the regional distribution of the alpha frequency which is higher in occipital than in frontal leads in the normal elderly. Spectral composition in the same group keeps its typical profile with age. Alpha-dominant tracings form 68%. Values collected from the two hemispheres are similar. Therefore, no evidence is detected for a selective age effect on one side, either right or left. In the elderly group, a sex-linked difference is found. Women have less delta and more beta frequency. The opposite holds true in men. EEG slowing is typical of old age. However, in occipital leads the alpha frequency has an average of 9.46 Hz. Statistical comparison between the normal groups (middle aged vs. elderly) gives no significant results. Significant differences are seen when the normal elderly are compared with demented subjects. The data do not support the hypothesis of a continuum from aging to mental deterioration.

A longitudinal EEG study of mild senile dementia of Alzheimer type: changes at 1 year and at 2.5 years

This longitudinal study of resting EEGs compared patients with senile dementia of Alzheimer type (SDAT) and healthy controls at 3 times of testing over a 2.5 year period. Measures included the mean EEG frequency as well as the percentage of power in alpha, beta, theta, and delta frequency bands obtained from power spectral analysis. The values from occipital to vertex derivations were averaged for the left and right hemispheres. In healthy older adults delta increased, and both beta and mean frequency decreased over the study period; there was no significant change in theta or alpha. In the SDAT group, all 5 EEG measures changed significantly; there were increases in delta and theta, and decreases in beta, alpha and mean frequency. Theta percentage power distinguished between all 4 stages of dementia (control, mild, moderate and severe). Other EEG measures discriminated only at certain stages. In the mild stage of SDAT theta, beta and mean frequency were already different from control values. In the moderate stage, these differences persisted, and alpha became different. Delta was the last to change, and in the present small sample of those with severe SDAT the difference had not yet reached significance.

Memory dysfunction and vigilance: neurophysiological and psychopharmacological aspects

Human brain function as measured by the computer-assisted spectral analyzed electroencephalogram (EEG) shows significant alterations in normal and pathological aging characterized by an increase of delta and theta activity and by a decrease of alpha and alpha-adjacent beta activity as well as by a slowing of the dominant frequency. These changes are indicative of deficits in the vigilance-regulatory systems. By the term vigilance we understand the availability and grade of organization of man's adaptive behavior, which in turn is dependent of the dynamic state of the total neural activity. An impairment of vigilance was found to be significantly correlated with the clinical symptomatology of the organic brain syndrome (OBS) as well as with mnestic performance deficits. Elderly subjects with bad memory exhibit slower activity and less alpha and alpha-adjacent beta activity than those with good memory. This was found to be true for both the time of acquisition and recall. Antihypoxidotic/nootropic drugs, such as the ergotalkaloids dihydroergotoxine and nicergoline, vincamine-alkaloids, piracetam, aniracetam, etiracetam, piridoxilate and others, induce interestingly just oppositional changes in human brain function, thereby improving vigilance. Other methods for proving therapeutic efficacy in man, like experimentally induced hypoxic hypoxidosis and the reversible alcoholic OBS, are discussed.

Senile dementia of the Alzheimer type

The prevalence of severe dementia in the United States is about 1.3 million cases, of which at least 50 to 60% are of the Alzheimer type. Severe dementia of the Alzheimer type is found rarely in a clearly dominant pattern, although often one or more relatives are affected. Down's syndrome in adults is often associated with Alzheimer changes. The diagnosis is a clinicopathological one; there is a considerable error rate in the clinical diagnosis early in the course of the disease, especially in regard to dementia in depression. The differential diagnosis involves a great many disorders, including multi-infarct dementia, tumors, subdural hematomas, and others. Physiological aspects of Alzheimer's disease include a diffusely slow electroencephalogram, reduced cerebral blood flow, and particular patterns noted on positron emission tomographic scanning. The latter technique has also demonstrated that oxygen extraction is normal in Alzheimer's disease, thus excluding ischemia from possible pathogenetic factors. Morphological changes, that is, the presence of plaques and tangles, are widely distributed in neocortex, paleocortex, and many deep gray areas down through the pontine tegmentum, but largely exclude the basal ganglia, thalamus, and substantia nigra. Numerous plaques without neocortical tangles are found in many demented persons older than 75 years. A severe loss of large neocortical neurons is characteristic of the disease. The chemical nature of the paired helical filaments that make up the neurofibrillary tangle has not yet been ascertained. Neurons are markedly deficient in the basal forebrain nuclei, and this deficiency may account for the severe diminution of choline acetyltransferase and acetylcholine in the neocortex and paleocortex. Muscarinic cholinergic receptors are present in normal amounts. Norepinephrine is reduced in some cases, and somatostatin in most. Substance P is low in severe cases. The etiology of the disorder is unknown and the role of aluminum is disputed. Management of patients with Alzheimer's disease is difficult, and neuroleptics are to be used with great caution because of their side effects. Substrate therapy has not been effective; physostigmine improves memory but is not suitable for general use. Trophic factors, gangliosides, and aluminum chelation are being investigated for use in pharmacological intervention.

Accuracy of clinical diagnosis in primary degenerative dementia: correlation with neuropathological findings

Neuropathological features and causes of death are presented in 27 deceased patients belonging to a prospective series of 71 hospitalised patients with primary degenerative dementia. The clinical criteria for primary degenerative dementia used in the present study were accurate enough to exclude patients with multi-infarct dementia. At necropsy, 82% of the cases had neuropathological changes of Alzheimer's disease. The clinical features of patients with other neuropathological changes are described. The most common immediate cause of death was bronchopneumonia which accounted for 59% of deaths in Alzheimer's disease.

EEG and computed tomography in the investigation of patients with senile dementia

Fifty-six patients with senile dementia of Alzheimer type and 84 normal elderly people were examined by EEG and computed tomography. In discriminant function analysis of the computed tomography indexes the highest discriminant function coefficient was for width of the third ventricle. Using computed tomography, the groups were correctly classified for 84% of the subjects. In discriminant function analysis of the EEG variables the highest discriminant function coefficient was for dominant occipital rhythm; the groups were correctly classified for 86% of the subjects. In discriminant function analysis of the width of the third ventricle, an index of cortical atrophy, the dominant occipital rhythm, age and sex, the width of the third ventricle had the highest discriminant function coefficient; the groups were correctly classified for 90% of the subjects.

Computed tomography findings in senile dementia and normal aging

Computed tomography (CT) findings in 57 patients with senile dementia of Alzheimer type (SDAT), 19 patients with multi-infarct dementia and 85 controls of similar age and sex were studied. The SDAT patients differed from the controls of ventricular dilatation, frontal horn index, cella media index and the width of the third ventricle, and also in the index of cortical atrophy. Even the least severely demented SDAT patients differed from the controls. In the SDAT group with the increasing degree of intellectual impairment the ventricular dilatation increased, but cortical atrophy did not correlate with the psychological test score. The multi-infarct dementia patients differed from the controls in all CT variables including local changes. The SDAT patients had a more marked ventricular dilatation than the multi-infarct dementia patients. The multi-infarct dementia patients had more frequently local changes in SDAT patients. In the control group age correlated with ventricular dilatation, and the lower test scores correlated with cortical atrophy in the left temporal region.

The EEG and differential diagnosis in psychogeriatrics

A model for differentiating cerebral dysfunction in senile, arteriosclerotic dementia, and depressive states is proposed on the basis of electrocortical topographic measures of EEG coherence. Bipolar EEGs were recorded from central, parietal, occipital and temporal areas in 24 elderly patients with a firm clinical diagnosis of senile dementia, senile arteriosclerosis or depression. Power and coherence spectra were computed on 20 second epochs recorded during eyes open, eyes closed and photic stimulation. Significant group differences were reported in both power and coherence measures. Power results were uniform for all channels but coherence values differed significantly with derivation. The best discriminator between groups was EEG coherence estimates between right parietal and temporal derivation. Correlations between clinical symptomatology and EEG coherence supported the direction of the discrimination between groups. The EEG coherence function is discussed as a potential measure of neuro-functional pathology in psychiatry.

Electroencephalography and computerised tomography in vascular and non-vascular dementia in old age

Nine normal elderly subjects and 81 patients with dementia have been studied by computerised tomography (CT) and electroencephalography (EEG). There was a broad relationship between slowing of the basic frequency of the EEG and the severity of mental impairment. Localised slow-wave activity was found in 19% of those with non-vascular dementia and 72% of those with dementia of vascular origin. The mean size of the ventricles, as determined from CT scans, was larger in the vascular than in the non-vascular group. Within the vascular group it was larger in those without than in those with visible infarcts. There was no relationship in either group between ventricular size and dominant EEG frequency.

Predictors of mortality in presenile and senile dementia

Forty-seven hospitalized patients with a diagnosis of presenile or senile dementia and without focal neurological disease of major systemic illness were given complete neurological, neuroradiological, and neuropsychological examinations. Mortality at one year after hospitalization was determined, 12 patients being lost to follow-up. Of the remaining 35 patients, 19 were alive and 1l had died. These groups did not differ in age, education, length of dementia history, sex, race, or degree of cerebral atrophy (by computerized tomography). Significant differences were found in degree of electroencephalographic abnormality and in 8 of 14 cognitive measures, the the largest single difference being on a test of expressive language. Discriminant function analysis made with the cognitive measures as dependent variables yielded a correct prediction (classification analysis) of mortality in all but 1 case (97% accuracy). These results suggest that (1) degree of functional brain impairment rather than degree of cerebral atrophy may be the more important influence on mortality in dementia patients without focal lesions, (2) short-term survival may be accurately predicted in such patients by tests of cognitive functioning, and (3) expressive language deficit in such patients may indicate a particularly poor prognosis for survival.