Electroencephalography as a Diagnostic Tool in Dementia

Abstract

Clinical electroencephalography is a relatively simple and inexpensive diagnostic tool with a high sensitivity for diffuse organic encephalopathy of various aetiologies but with a rather low specificity for the type of diagnosis. The highest sensitivity is shown in DAT and Parkinson dementia, and in these conditions the degree of EEG abnormality is correlated with the disease severity. Quantification of EEG makes these correlations more reliable and provides a method for monitoring therapeutic effects. Dementias with predominantly frontal pathology show much less EEG abnormality, and in these conditions the EEG is often normal despite obvious clinical dementia. Also, alcohol dementias often show normal EEG patterns. At an early stage of clinical evaluation, EEG may be useful in the discrimination of organic dementia from pseudodementia, because EEG is usually normal in depression, confusion, agitation and other psychiatric conditions. In pseudodementia due to intoxication with sedatives the EEG is usually dominated by diffuse β activity. At the stage of differential diagnosis of an organic brain disorder, EEG cannot reliably discriminate between encephalopathies secondary to hydrocephalus, AIDS, cerebrovascular disease, B12 deficiency and primary degenerative diseases such as DAT. More specific EEG patterns are seen in acute cerebrovascular lesions, metabolic encephalopathies, i.e. of hepatic origin, Creutzfeldt-Jakob disease, herpes encephalitis, and nonconvulsive status epilepticus as possible causes of a rapidly deteriorating mental and neurological condition. Repeated EEG recordings over time would add significantly to the diagnostic information. New techniques such as topographical brain mapping, analysis of the EEG during REM sleep, coherence analysis of the EEG activity, and the combination of quantified EEG techniques with evoked potentials and event-related potentials will presumably add to the sensitivity as well as the specificity of the electrophysiological methods in the diagnosis of dementia.

Acute Nicotine Administration in Alzheimer’s Disease: An Exploratory EEG Study

“…These spectrum-analyzed indices of EEG slowing, observed to the same degree in both THA-and nontreated patients, have been reported previously in a large number of studies comparing DAT patients with agematched controls [40]. EEG slowing generally tends to increase in relation to disease progression, but the specific spectral band index (i.e.…”

“…Quantitative EEG has not only proven to be useful in the acute prolifing of new cognitiveenhancing agents and in therapeutic assessment of clinical trials in dementia [43][44][45][46], it has also been of use in the diagnoses of DAT in that it has addressed aspects of cerebral electrical potential disturbances which are not easily appreciated visually in the traditional clinical EEG [40,67]. In this present study, these dual functions of EEG in DAT have been addressed, and although the presence of significant observations strengthens the utility of this noninvasive physiologic CNS probe, the exploratory results with small samples must be treated cautiously, especially as they are not viewed in the context of clinical/cognitive (and adverse effects) assessments which could have provided useful insights into the behavioral impact of nicotine-induced EEG alterations in DAT.…”

“…Electroencephalography (EEG) shows the central arousal response to smoke-inhaled nicotine characterized by power spectrum shifts with nicotine reducing power in slow (delta and theta)-wave frequencies and increasing power in fast (alpha and beta)-wave frequencies [35][36][37][38][39]. The EEG profile of DAT itself has been shown to be dominated by slow-wave activity and diminished fast-wave activity [40], and acute administration of cholinergic agonists (e.g. physostigmine) have tended to exert an opposing action, reducing slow-wave power, augmenting fastwave power and generally shifting the EEG power spectrum of patients into more normal patterns [41].…”

Objective Assessment of the Degree of Dementia by Means of EEG

“…Thus, a normal EEG gives cause for a careful reconsideration of the diagnosis of dementia, taking into account that the clinical picture may be obscured by a depressive disorder [2,3]. While the contribution of morphological methods, such as CT [4] or MRI [5], mostly consists of distinguishing secondary forms of dementia, EEG reflects the disturbed cortical function resulting in dementia [6]. The diagnostic relevance of EEG in dementia seems to be comparable with that of the more complicated and therefore less accessible PET [7,8].…”

Non-convulsive status epilepticus in adults - an overview

“…Chronically progressing conditions causing seizures encompass all the different forms of neurodegenerative disorders, like Alzheimer's disease, frontotemporal dementia spectrum, cerebral amyloid angiopathy, etc. [123,124]. Several metabolic conditions may be associated with NCSE as an epileptic reaction to the changed cerebral physiological environment.…”