Neurometrics in cerebral ischemia and uremic encephalopathy

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.

Spectral and complexity features of the EEG changed by visual input in a case of subcortical stroke compared to healthy controls

OBJECTIVE

To compare spectral and complexity characteristics of the EEG in a unique case of subcortical infarct to those seen in healthy controls.

METHODS

Absolute and relative frequency spectra, theta/beta ratio, the brain symmetry index (BSI), Omega-complexity and synchronization likelihood were calculated of the EEG recorded in eyes closed and eyes open conditions.

RESULTS

Increased absolute delta, theta, and Omega-complexity in these frequency bands, higher theta/beta ratios, and decreased relative beta activity were found in the side of the infarct. The BSI localized the excess of slow, and decrease of fast frequency activity to the area of ischemia. Following eyes opening the increase of fast and decrease of slow frequencies, the increase of Omega-complexity in the alpha and beta bands, and the decrease of synchronization likelihood for the fast frequency bands were reduced in the side of the infarct.

CONCLUSIONS

The subcortical infarct caused ipsilaterally increased slow, and decreased fast frequency activity accompanied by decreased synchronization of slow, increased synchronization of fast frequencies. Reduced reactivity in the ischemic side was particularly apparent for complexity measures.

SIGNIFICANCE

Complexity indices of the EEG are sensitive complementary measures of electrophysiological changes caused by local lesions such as subcortical stroke.

[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.

Effects of rHuEPO on Q-EEG and event-related potentials in chronic renal failure

Quantitative electroencephalography is a powerful tool to evaluate brain function, and preliminary data have shown its usefulness in the evaluation of patients with chronic renal failure (CRF). In this study, baseline values of different quantitative EEG variables, as well as data from the P300 component of the visual event-related potential, in 43 patients with chronic renal failure, were compared with those of a group of healthy subjects and with the results obtained after 3, 6, 9 and 12 months of treatment of these patients with rHuEPO. Baseline total power was much lower in patients with CRF than in healthy subjects, and the distribution of power among the frequency bands was also abnormal. rHuEPO promptly normalized total power and progressively improved power distribution, although full normality was not achieved. Mean dominant frequencies in brain areas were abnormal in patients with CRF, and progressive improvement was seen along the study. The latency of P300, which was increased before treatment, decreased in all subjects, but normal values were not reached. The same applies to the hypomanic and psychopathic scores of psychological tests. Altogether, brain dysfunction of CRF seems to substantially improve by treatment of the anemia with rHuEPO.