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Computerized EEG frequency analysis

Sensitivity and specificity in patients with focal lesions

Department of Neurology and Clinical Neurophysiology Laboratory, Oregon Health Sciences University, Portland, OR (Drs. Oken and Salinsky)
Department of Neurology and Clinical Neurophysiology Laboratory, Massachusetts General Hospital, Boston, MA. (Dr. Chiappa)

We performed computerized EEG frequency analysis (C-EEGFA) in 69 controls and 20 patients with focal brain lesions and focally abnormal conventional EEGs. Individual channel EEG frequency analysis variables that were helpful in differentiating the 2 groups were absolute delta and theta band power, relative delta, theta, and alpha band powers, and median-power frequency. High-frequency beta band power (20 to 32 Hz) was not useful. Changes in EEG with age were seen only after age 50 and generally consisted of an increase in anterior alpha power, with no significant increase in slowing. Correlations of C-EEGFA variables with posterior alpha power were more significant than correlations with age. Calculating normative C-EEGFA data for 5 subsets of controls, each with a different amount of posterior alpha power, increased the sensitivity of the EEG frequency analysis test without altering the specificity. Even with this correction, 2 of 20 patients with focal lesions and focally abnormal conventional EEGs had normal C-EEGFA studies. If these obvious focal lesions produced normal results, more subtle diseases might not be detected. A significant clinical utility of C-EEGFA remains to be proven.

Address correspondence and reprint requests to Dr. Oken, Clinical Neurophysiology Lab, L-348, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, OR 97201.

Presented in part at the thirty-seventh annual meeting of the American Academy of Neurology, Dallas, TX, April 1986, and the American EEG Society, September

1988.

Received March 6, 1989. Accepted for publication in final form April 11, 1989.