How to solve problems using the labor-management partnership.
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L Morehead
Publications and source records attributed to L Morehead.
Intraindividual analysis of antiepileptic drug effects on EEG background rhythms.
Antiepileptic drug (AED) therapy with either phenytoin or carbamazepine has been associated with generalized slowing of EEG background rhythms. These effects have been seen in groups of patients undergoing AED manipulation, although the background slowing has been highly variable from patient to patient. Background slowing may represent an objective physiologic measure of drug impact on cerebral function and could be useful in monitoring for AED neurotoxicity in individual patients. This would require an intraindividual analysis of AED effects on EEG background rhythms. The present study was designed to develop a methodology for intraindividual analysis of EEG background changes and to apply this methodology to patients beginning or ending chronic AED therapy. EEG recordings were obtained under controlled conditions in 31 healthy subjects and were repeated after an interval of 12-16 weeks. EEG background rhythms from each record were analyzed using the fast Fourier transform, and test-retest differences for several quantitative measures were calculated from each subject's paired recordings. EEG recordings were also obtained in 6 patients beginning or ending chronic AED therapy. Test-retest differences for each patient's quantitative EEG measures were statistically compared with the distributions of test-retest measures obtained from the healthy controls. AED therapy was associated with an increase in absolute delta and/or theta power and a slowing of the dominant posterior rhythm; however, these EEG background changes varied widely in degree from patient to patient. Intraindividual analysis revealed that 5 patients had statistically significant slowing relative to the control group on at least 1 of the 9 target quantitative EEG measures, as well as a composite measure.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
A comparison of quantitative EEG frequency analysis and conventional EEG in patients with focal brain lesions.
The sensitivity and specificity of quantified EEG frequency analysis (EEGFA) were assessed in a group of patients with CT or MRI verified unilateral cerebral lesions and compared with the results of conventional EEG interpretations. Digital EEG recordings were obtained in 25 patients and 25 normal control subjects during performance of an alerting task. Recording artifacts were carefully eliminated. The results of EEGFA were then statistically compared with those of 75 additional normal subjects in the same age range. Complete conventional EEGs were blindly interpreted by two independent electroencephalographers using a structured reporting procedure. We observed similar overall sensitivities for the two methods. Optimal yield for EEGFA was associated with the use of longer edited EEG lengths, longitudinal bipolar montage, and normative data based on total EEG power. In those recordings with normal or mildly abnormal EEG backgrounds the two techniques were to an extent complimentary, each detecting abnormalities missed by the other. In such circumstances EEGFA may be useful as an extension of conventional EEG interpretation.
Adult↗
Test-retest reliability in EEG frequency analysis.
This study was performed to gain a better understanding of EEG frequency analysis test-retest reliability in normal healthy adults, and to evaluate factors which could influence the measured inter-record differences. Nineteen subjects underwent serial EEG recordings at 5 min and 12-16 week intervals. Records were visually edited using a standardized protocol, and FFT frequency analysis performed on segments of 60, 40, or 20 sec total length. Correlation coefficients for broad band features averaged 0.92 over the 5 min retest interval and 0.84 over the 12-16 week interval. There was essentially no difference between correlation coefficients of absolute and relative power features. Coefficients based on 60 sec records were marginally higher than those of 40 or 20 sec records. On the other hand, test-retest percent differences were typically lower for relative as opposed to absolute power features, and 60 sec records showed consistently lower percent differences than did 40 or particularly 20 sec records. Peak alpha frequency and mean frequency were the most stable EEG features at either interval. Montage had significant effects on test-retest differences at the 12-16 week interval. A significant association between intra-record and inter-record variability could not be demonstrated.
Brain↗