Topographic maps of brain electrical activity in primary degenerative dementia of the Alzheimer type and multiinfarct dementia

EEG measures for clinical research in major vascular cognitive impairment: recommendations by an expert panel

Vascular contribution to cognitive impairment (VCI) and dementia is related to etiologies that may affect the neurophysiological mechanisms regulating brain arousal and generating electroencephalographic (EEG) activity. A multidisciplinary expert panel reviewed the clinical literature and reached consensus about the EEG measures consistently found as abnormal in VCI patients with dementia. As compared to cognitively unimpaired individuals, those VCI patients showed (1) smaller amplitude of resting state alpha (8-12 Hz) rhythms dominant in posterior regions; (2) widespread increases in amplitude of delta (< 4 Hz) and theta (4-8 Hz) rhythms; and (3) delayed N200/P300 peak latencies in averaged event-related potentials, especially during the detection of auditory rare target stimuli requiring participants' responses in "oddball" paradigms. The expert panel formulated the following recommendations: (1) the above EEG measures are not specific for VCI and should not be used for its diagnosis; (2) they may be considered as "neural synchronization" biomarkers to enlighten the relationships between features of the VCI-related cerebrovascular lesions and abnormalities in neurophysiological brain mechanisms; and (3) they may be tested in future clinical trials as prognostic biomarkers and endpoints of interventions aimed at normalizing background brain excitability and vigilance in wakefulness.

The Role of Quantitative EEG in the Diagnosis of Neuropsychiatric Disorders

Quantitative electroencephalography (QEEG) is a modern type of electroencephalography (EEG) analysis that involves recording digital EEG signals which are processed, transformed, and analyzed using complex mathematical algorithms. QEEG has brought new techniques of EEG signals feature extraction: analysis of specific frequency band and signal complexity, analysis of connectivity, and network analysis. The clinical application of QEEG is extensive, including neuropsychiatric disorders, epilepsy, stroke, dementia, traumatic brain injury, mental health disorders, and many others. In this review, we talk through existing evidence on the practical applications of this clinical tool. We conclude that to date, the role of QEEG is not necessarily to pinpoint an immediate diagnosis but to provide additional insight in conjunction with other diagnostic evaluations in order to objective information necessary for obtaining a precise diagnosis, correct disease severity assessment, and specific treatment response evaluation.

Regional functional connectivity predicts distinct cognitive impairments in Alzheimer's disease spectrum

Understanding neural network dysfunction in neurodegenerative disease is imperative to effectively develop network-modulating therapies. In Alzheimer’s disease (AD), cognitive decline associates with deficits in resting-state functional connectivity of diffuse brain networks. The goal of the current study was to test whether specific cognitive impairments in AD spectrum correlate with reduced functional connectivity of distinct brain regions. We recorded resting-state functional connectivity of alpha-band activity in 27 patients with AD spectrum − 22 patients with probable AD (5 logopenic variant primary progressive aphasia, 7 posterior cortical atrophy, and 10 early-onset amnestic/dysexecutive AD) and 5 patients with mild cognitive impairment due to AD. We used magnetoencephalographic imaging (MEGI) to perform an unbiased search for regions where patterns of functional connectivity correlated with disease severity and cognitive performance. Functional connectivity measured the strength of coherence between a given region and the rest of the brain. Decreased neural connectivity of multiple brain regions including the right posterior perisylvian region and left middle frontal cortex correlated with a higher degree of disease severity. Deficits in executive control and episodic memory correlated with reduced functional connectivity of the left frontal cortex, whereas visuospatial impairments correlated with reduced functional connectivity of the left inferior parietal cortex. Our findings indicate that reductions in region-specific alpha-band resting-state functional connectivity are strongly correlated with, and might contribute to, specific cognitive deficits in AD spectrum. In the future, MEGI functional connectivity could be an important biomarker to map and follow defective networks in the early stages of AD.

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Magnetoencephalographic imaging (MEGI) measures brain functional connectivity.

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We investigated MEGIalpha-band connectivity in a cohort with Alzheimer’s disease spectrum.

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Decreased connectivity of multiple brain regions correlates with disease severity.

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Decreased connectivity of focal brain regions correlates with cognitive deficits.

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MEGI is a novel, unbiased approach to map neural network defects in dementia.

Alzheimer's disease qEEG: spectral analysis versus coherence. Which is the best measurement?

There is evidence in electroencephalography that alpha, theta and delta band oscillations reflect cognitive and memory performances and that quantitative techniques can improve the electroencephalogram (EEG) sensitivity. This paper presents the results of comparative analysis of qEEG variables as reliable markers for Alzheimer's disease (AD). We compared the sensitivity and specificity between spectral analysis (spectA) and coherence (Coh) within the same group of AD patients. SpectA and Coh were calculated from EEGs of 40 patients with mild to moderate AD and 40 healthy elderly controls. The peak of spectA was smaller in the AD group than in controls. AD group showed predominance of slow spectA in theta and delta bands and a significant reduction of inter-hemispheric Coh for occipital alpha 2 and beta 1 and for frontal delta sub-band. ROC curve supported that alpha band spectA was more sensitive than coherence to differentiate controls from AD.

Diagnosis of Alzheimer's disease in Brazil: Supplementary exams

This article presents a review of the recommendations on supplementary exams employed for the clinical diagnosis of Alzheimer's disease (AD) in Brazil published in 2005. A systematic assessment of the consensus reached in other countries, and of articles on AD diagnosis in Brazil available on the PUBMED and LILACS medical databases, was carried out. Recommended laboratory exams included complete blood count, serum creatinine, thyroid stimulating hormone (TSH), albumin, hepatic enzymes, Vitamin B12, folic acid, calcium, serological reactions for syphilis and serology for HIV in patients aged younger than 60 years with atypical clinical signs or suggestive symptoms. Structural neuroimaging, computed tomography or - preferably - magnetic resonance exams, are indicated for diagnostic investigation of dementia syndrome to rule out secondary etiologies. Functional neuroimaging exams (SPECT and PET), when available, increase diagnostic reliability and assist in the differential diagnosis of other types of dementia. The cerebrospinal fluid exam is indicated in cases of pre-senile onset dementia with atypical clinical presentation or course, for communicant hydrocephaly, and suspected inflammatory, infectious or prion disease of the central nervous system. Routine electroencephalograms aid the differential diagnosis of dementia syndrome with other conditions which impair cognitive functioning. Genotyping of apolipoprotein E or other susceptibility polymorphisms is not recommended for diagnostic purposes or for assessing the risk of developing the disease. Biomarkers related to the molecular alterations in AD are largely limited to use exclusively in research protocols, but when available can contribute to improving the accuracy of diagnosis of the disease.

Improving Alzheimer's disease diagnosis with machine learning techniques

There is not a specific test to diagnose Alzheimer's disease (AD). Its diagnosis should be based upon clinical history, neuropsychological and laboratory tests, neuroimaging and electroencephalography (EEG). Therefore, new approaches are necessary to enable earlier and more accurate diagnosis and to follow treatment results. In this study we used a Machine Learning (ML) technique, named Support Vector Machine (SVM), to search patterns in EEG epochs to differentiate AD patients from controls. As a result, we developed a quantitative EEG (qEEG) processing method for automatic differentiation of patients with AD from normal individuals, as a complement to the diagnosis of probable dementia. We studied EEGs from 19 normal subjects (14 females/5 males, mean age 71.6 years) and 16 probable mild to moderate symptoms AD patients (14 females/2 males, mean age 73.4 years. The results obtained from analysis of EEG epochs were accuracy 79.9% and sensitivity 83.2%. The analysis considering the diagnosis of each individual patient reached 87.0% accuracy and 91.7% sensitivity.

Does EEG montage influence Alzheimer's disease electroclinic diagnosis?

There is not a specific Alzheimer's disease (AD) diagnostic test. AD diagnosis relies on clinical history, neuropsychological, and laboratory tests, neuroimaging and electroencephalography. Therefore, new approaches are necessary to enable earlier and more accurate diagnosis and to measure treatment results. Quantitative EEG (qEEG) can be used as a diagnostic tool in selected cases. The aim of this study was to answer if distinct electrode montages have different sensitivity when differentiating controls from AD patients. We analyzed EEG spectral peaks (delta, theta, alpha, beta, and gamma bands), and we compared references (Biauricular, Longitudinal bipolar, Crossed bipolar, Counterpart bipolar, and Cz reference). Support Vector Machines and Logistic Regression classifiers showed Counterpart bipolar montage as the most sensitive electrode combination. Our results suggest that Counterpart bipolar montage is the best choice to study EEG spectral peaks of controls versus AD.

The clinical use of quantitative EEG in cognitive disorders

The primary diagnosis of most cognitive disorders is clinically based, but the EEG plays a role in evaluating, classifying and following some of these disorders. There is an ongoing debate over routine use of qEEG. Although many findings regarding the clinical use of quantitative EEG are awaiting validation by independent investigators while confirmatory clinical follow-up studies are also needed, qEEG can be cautiously used by a skilled neurophysiologist in cognitive dysfunctions to improve the analysis of background activity, slow/fast focal activity, subtle asymmetries, spikes and waves, as well as in longitudinal follow-ups.

qEEG spectral peak in Alzheimer's disease: A possible tool for treatment follow-up

qEEG spectral analysis has been considered highly sensitive to cortical functional changes and agrees strongly with the clinical diagnosis of AD. The sensitivity of spectral analysis has ranged from 71% to 81% in several studies.1-3.

OBJECTIVE

The aim of this study was to retrospectively evaluate whether alpha qEEG spectral peak can supplement clinical examination by constituting an independent tool to monitor treatment and follow-up of dementia progression in Alzheimer's disease (AD). In addition, we examined the demographic data and alpha power spectra distribution of patients and elderly normal controls.

METHODS

qEEGs were selected from 2 groups of patients: normal controls (n=30), and patients who fulfilled criteria for mild probable AD diagnosis (n=41). The alpha qEEG spectral analysis and MMSE were performed once or twice a year.

RESULTS

In our groups, MMSE scores and qEEG alpha spectral peak were unchanged (no statistical differences) after anticholinesterase use where qEEG spectral peak was never lower than 8 Hz in the control group.

CONCLUSION

This study supports two important concepts. First, 8 Hz alpha appears to be the lowest awake spectral peak compatible with normality. And finally, in a clinical context, qEEG is a valuable diagnostic tool that could prove useful for Dementia follow-up.

Neurophysiologic correlates of psychiatric disorders and potential applications in epilepsy

There is increasing interest in psychiatric assessment using neurophysiologic tools such as electroencephalography (EEG), magnetoencephalography (MEG), and transcranial magnetic stimulation (TMS). This is because these technologies have good temporal resolution, are relatively noninvasive, and (with the exception of MEG) are economical. Many different experimental paradigms and analysis techniques for the assessment of psychiatric patients involving these technologies are reviewed including conventional quantitative electroencephalography (QEEG), EEG cordance, low-resolution electromagnetic tomography (LORETA), frontal midline theta, midlatency auditory evoked potentials (P50, N100, P300), loudness dependency of the auditory evoked potential (LDAEP), mismatch negativity (MMN), contingent negative variation (CNV), and transcranial magnetic stimulation (TMS). Many of these neurophysiologic stimulus paradigms hold the promise of improving psychiatric patient care by improving diagnostic precision, predicting treatment response, and providing new phenotypes for genetic studies. Large cooperative multisite studies need to be designed to test and validate a few of these paradigms so that they might find use in routine clinical practice.

Magnetoencephalographic analysis of cortical activity in Alzheimer's disease: a pilot study

OBJECTIVES

In the present study, MEG was used to analyze spectral power and reference-free coherence in patients with probable Alzheimer's disease (AD).

METHODS

Sixty-one channel MEG was recorded in 5 AD patients and 5 age-matched controls at rest with eyes open and eyes closed, as well as during the performance of two different mental tasks. Artefact-free epochs were selected for the analysis of power and coherence values in each of 5 4-Hz wide frequency bands ranging from 2 to 22 Hz.

RESULTS

In AD patients, the absolute low frequency magnetic power was significantly and rather diffusely increased relative to controls with a fronto-central maximum. High frequency power values were significantly decreased over the occipital and temporal areas. Reactivity to eye-opening and mental tasks was reduced in the patient group. Relative to controls, a general decrease of MEG coherence values, including all frequencies analyzed, was found in AD patients.

CONCLUSIONS

These observations confirm the pattern of changes in spectral power and reactivity known from EEG studies and suggest that coherence decreases in AD patients are widespread and include frequencies outside the alpha band.

[Vascular dementia: diagnostic challenge and treatment]

BACKGROUND

Treatment of vascular dementia depends on accurate diagnosis and criteria for evaluation of therapeutic responses that are not well standardized.

METHODS

Diagnostic criteria for vascular dementia, tools for the assessment of its clinical course and current treatment options are sequentially reviewed.

RESULTS

Strict diagnostic criteria with high specificity should be selected in clinical trials. Tools for sequential assessment are not standardized. Clinical endpoints of real value for patients and caregivers are usually excluded from analysis. Prevention of recurrent cerebrovascular events is the only known treatment for stabilization and eventually recovery of cognitive and behaviour disturbances. Benefit may be obtained by adapting hospital or home environment and introducing daily routines minimizing stress and fatigue. The use of non-specific cerebral stimulants and so-called neuroprotective drugs is controversial. Careful neuropsychological evaluation guiding management of specific deficits and the use of psychiatric drugs in selected situations may also be useful.

CONCLUSION

Strict criteria for the diagnosis of vascular dementia and for the evaluation of treatment responses should be used in drug trials. Aside the secondary prevention of stroke, no drug therapy influencing cognition or neuronal damage has been proved to be useful in patients with vascular dementia.

A comparison of qEEG and HMPAO-SPECT in relation to the clinical severity of Alzheimer's disease

Electroencephalographical studies have disclosed correlations between topographical features of Fast Fourier Transformation maps and the severity of Alzheimer's disease (DAT). The object of the present study was to explore the relations of HMPAO-SPECT and quantitative EEG (qEEG) with the severity of dementia. Twenty-three patients were included in the study. Spectral and topographical EEG parameters were compared with global and regional cerebral blood flow, and with psychometric measures of clinical severity. None of the regions of interest of the SPECT scans were significantly correlated with clinical severity. Low values in delta- and theta bands, however, were related to high scores on the Mini-Mental-State examination (P < 0.01), whereas the Syndrome-Kurz test correlated inversely with the power values in the alpha and beta band. The global decrease in cerebral blood flow (CBF) was associated with a shift on the topographical alpha-centroids in the posterior direction (P < 0.01). In previous studies correlations between CBF and clinical severity were weak, indicating a high interindividual variance, or interactions with concomitant vascular lesions. Whereas SPECT is a well-established tool for the diagnosis of dementia, the present study indicates qEEG as a potential marker for the staging of the cognitive decline in DAT.

Quantified-EEG in normal aging and dementias

The value of quantitative electroencephalography (q-EEG) in the differential diagnosis of multi-infarct dementia (MID) and dementia of Alzheimer's type (DAT) is controversial. To evaluate the possible diagnostic role of q-EEG in these two conditions we studied 18 healthy adults, 16 healthy elderly (HE), 29 DAT patients and 45 MID patients. MID patients showed a significant increase of delta activity on the occipital regions, a significant widespread increase of theta activity, a significant widespread decrease of alpha activity. DAT patients showed a significant widespread increase of delta and theta activity, a significant widespread decrease of alpha activity. Spectral profile analysis showed an asymptotic exponential peak frequency at 4.33 HZ, and the disappearance of dominant activity in DAT patients; a 1 Hz decrease of peak frequency with a preserved normal profile in MID patients. We conclude that q-EEG is a useful ancillary test to differentiate MID from DAT.

Topography of the maximum of the amplitude of EEG frequency bands in dementia of the Alzheimer type

The localization of the maxima of activity of 36 patients with dementia of the Alzheimer type and 36 age-matched controls was calculated after Fourier transformation of EEG data in six frequency bands (4 Hz steps between 1 and 24 Hz). Patients were divided into three groups of severity (BCRS mean < 3,9, 4.0-4.9, and > 4.9). Significant differences were found in the beta frequency band. In the distribution of the maxima of the activity, the maxima of patients were located more frontally than the maxima of controls. The alterations were staged dependent. The beta activity in EEG is said to be correlated with cognitive processes; the correlation between cognitive decline and decreasing beta activity in dementia of the Alzheimer type might support this assumption. Differences in the location of the maxima between patients and controls might allow for differentiation between both groups.

Canadian guidelines for the development of antidementia therapies: a conceptual summary

The magnitude of the problems faced by Canadian society as a result of an aging population has been identified. Perhaps the most important concern related to this greying of Canada is the increasing incidence of dementia and Alzheimer's disease. Therapeutic options for these disorders have been limited to date. Advances in biotechnology and molecular biology will offer novel approaches to treatment. These and the expansion of more traditional therapeutic avenues require guidelines with the aim of optimizing their development.

Discrimination between demented patients and normals based on topographic EEG slow wave activity: comparison between z statistics, discriminant analysis and artificial neural network classifiers

The topographic distributions of absolute delta and theta powers were used to classify demented patients and normals by means of z statistics, discriminant analysis and artificial neural networks (NN). The data were taken from two psychopharmacological studies in mildly to moderately demented patients (111 and 96 patients for studies I and II, respectively) and from 56 normal healthy controls. All patients were diagnosed according to DSM-III criteria and were free of medication for at least 2 weeks. The NN used was a strictly layered feed-forward network with complete connections. The z-transformed absolute power values in the combined delta and theta frequency range at 17 electrodes, recorded in a 3 min vigilance-controlled EEG with eyes closed, were used as input. After having trained the NN successfully by backpropagating of errors, the generalization test with independent data results in a classification performance of 90% determined by "relative operating characteristic" analysis. The NN out-performed z statistics and discriminant analysis. This high percentage of correct classifications may justify the development of further application of NNs based on topographic EEG data.

Quantitative topographical EEG compared to FDG PET for classification of vascular and degenerative dementia

Quantitative topographical EEG was compared with regional glucose metabolism measured by PET with respect to the sensitivity in the classification of mild to moderate dementia. In 24 patients with probable Alzheimer's disease (DAT), 19 patients with vascular dementia (VD) and 15 age-matched healthy controls, global and regional EEG and PET data were analyzed. The metabolic ratio between typically affected and non-affected regions differentiated between DAT and VD (P < 0.001) as well as between DAT and normal controls (P < 0.001) even for the subgroup of mild dementia. In contrast to PET, global EEG changes were more sensitive than regional alterations for the classification into the respective groups. Relative theta power was most sensitive for the differentiation of demented patients irrespective of type of normal controls (P < 0.01), whereas OCC/FR alpha ratio (occipital divided by frontal power) separated between dementia types (P < 0.01) as well as between DAT and normals (P < 0.05). Additionally, EEG may help to grade severity especially in DAT. Combined use of EEG and PET was more discriminative and reached higher diagnostic specificity than each test individually. These results suggest that EEG and PET are complementary diagnostic procedures for the differentiation and classification of dementias.

Two-Hz wide EEG bands in Alzheimer's disease

Twenty Alzheimer's Disease (AD) patients in a mild to moderate stage of the disease and 20 control subjects were compared in 17 2-Hz wide bands from the electrodes 01, 02, P3, P4, T5, T6, F3, F4, F7, F8, Fp1, and Fp2. Differences reached statistical significance for 0-2 and 4-6 Hz bands, where AD patients presented highest power values. The AD group was divided into two groups according to the stage of disease. Both groups of patients presented 0-2 Hz increase in frontal, right parieto-temporal, and occipital areas. The increase in 4-6 Hz band was mainly over frontal areas in both groups and over left parietal region in moderate AD patients. These results and those relative to dominant frequency and crossover frequency between groups are discussed according to previous results with conventional and 2-Hz wide bands in AD patients in a severe stage of the disease.

EEG mapping and psychopharmacological studies with denbufylline in SDAT and MID

Computed tomography (CT), electroencephalograms (EEG), clinical and psychometric data were obtained in 96 mildly to moderately demented patients (72 women, 24 men), aged 61-96 years (mean 82), diagnosed according to DSM-III criteria. Patients were off drugs for at least 2 weeks and subdiagnosed according to the modified Marshall-Hachinski ischemic score and CT in 45 senile dementia of the Alzheimer type (SDAT) and 51 multiinfarct dementia (MID) patients. Evaluations were carried out before and 12 weeks after treatment with either 100 mg denbufylline BID or placebo and included EEG mapping, the Sandoz Clinical Assessment Geriatric (SCAG) score/factors, the Clinical Global Impression (CGI), the Digit Symbol Substitution Test (DSST), the Trail-Making Test (TMT) and the Digit Span Test (DS). Descriptive data analysis including confirmatory statements found delta/theta activity enhanced, alpha and beta activity reduced, total power augmented, and the centroid slowed down over various brain regions in patients as compared with controls. The two subtypes of dementia could be differentiated in some conventional EEG variables but mostly by means of power asymmetry indices. Denbufylline induced a statistically significant and clinically relevant improvement in both SDAT and MID patients, whereas after placebo this was not the case in CGI, the TMT, and the DS, with interdrug differences being significant in all primary target variables such as the CGI, MMS, SCAG, and DSST. Thus, both the degenerative and vascular type of dementia exhibited a therapeutic benefit that could be objectified at the neurophysiological level by EEG mapping in an improvement of vigilance.

Quantitative EEG mapping and PET in Alzheimer's disease

Quantitative analysis of topographical EEG was studied in comparison with measurement of regional glucose metabolism by PET in 42 patients with clinical diagnosis of probable dementia of Alzheimer type (AD) and in 15 age-matched normal controls. Measures analyzed included global and regional data from areas typically affected and not affected by AD pathology. While disturbance of metabolism followed a typical regional pattern, relative alpha, theta and delta power were more globally altered without selectivity for specific regions. Separation between AD and age matched controls by relative theta power was correct in 86% and was close to that by temporo-parietal glucose metabolism (correct classification 87%). Relative theta power as well as temporo-parietal glucose metabolism were significantly correlated (tau B = 0.54 and -0.53, respectively) to severity of AD assessed by the global deterioration scale. These results indicate that EEG measures may be used with an accuracy close to metabolic values from PET for the assessment of severity of AD.

Acute and chronic antidepressant drug treatments induce opposite effects in the social behaviour of rats

Clinical studies indicate that the behavioural responses/reactions of depressed patients to environmental and social stimulation are modified during remission from depressive illness, and require continuous (at least 3 weeks) drug treatment. In order to determine whether antidepressant drugs modify the behavioural patterns of experimental animals in ways that may be related to their ability to modify human reactive behaviour, we have examined the effects of acute and chronic treatment with clomipramine, fluoxetine, iprindole, mianserin and phenelzine (antidepressants with markedly different acute pharmacology) on the behaviour exhibited by rats during social interaction (SI). Acute treatment of short-term isolated resident rats with non-sedative doses of each antidepressant drug selectively and dose-relatedly reduced aggressive behaviour exhibited during SI. Conversely, haloperidol (antipsychotic) or diazepam (anxiolytic) only reduced aggressive behaviour at sedative doses. In comparison, following chronic treatment, all antidepressants examined, but not haloperidol or diazepam, increased aggressive behaviour exhibited by resident rats during SI which returned to the pre-treatment level by 7 or (after phenelzine) 14 days after the cessation of treatment. It is concluded that the antidepressants examined induce selective, diametrically opposite effects on rodent aggressive behaviour following acute and chronic treatment which is indicative of antidepressant efficacy. Furthermore, it is argued that the increased aggressive behaviour following chronic antidepressant drug treatment may indicate a disinhibition of social behaviour in the rat that mirrors the externalization of emotions associated with the remission of depressive illness.