Diagnostic yield of standard-wake and sleep EEG recordings.

OBJECTIVE:To investigate whether Posterior Dominant Rhythm (PDR) can be reliably assessed in sleep-EEG recordings and to investigate the diagnostic yield of standard-wake and sleep-recordings. METHODS:EEG recordings of 303 consecutive patients aged 18-88 years were analyzed. All patients had both standard-wake and sleep-recordings, including patients who had abnormal standard recordings. Melatonin was used in 6% of sleep EEGs, and sleep deprivation in 94%. The mean duration of sleep was 41 min. We measured the PDR frequency in standard and sleep-recordings, both before and after sleep. We compared the diagnostic yield of standard-wake and sleep EEG recordings. RESULTS:Compared to standard EEG, sleep-recordings showed a significantly lower PDR frequency, both when measured before and after sleep (p < 0.001). One-hundred-fifty-six patients (51%) had normal standard recordings, and 35 of them (22%) had abnormal findings in the sleep-recording. One-hundred-forty-seven patients had abnormal standard recordings and in 16 of them (11%) these abnormalities were not present in sleep-recording. CONCLUSIONS:PDR is significantly slower in the wake periods of sleep-recordings, compared to standard wake recordings. SIGNIFICANCE:Sleep and standard wake recordings are complementary.