Abstracts

Rationale: Periodic EEG patterns have been typically associated with stuporous or comatose states in ICU patients. Occasionally, however, patients with these patterns are alert and can follow commands. The purpose of this study was to identify the electrographic characteristics of periodic patterns with an alert state of consciousness. Methods: 30-seconds-EEG segments with a continuous periodic pattern were selected randomly from consecutive 24-hour prolonged video-EEG recordings of 16 consecutive patients admitted in the ICU. Three electroencephalographers rated the recordings independently and blind to the clinical data. Recordings were classified according to: 1) their periodicity (into periodic or semi-periodic); 2) their distribution (generalized, lateralized [involving the entire hemisphere], regional [involving an entire lobe] or focal [involving sub-lobar regions]; 3) their localization (as frontal, temporal, parietal, occipital, or if it involved more than one lobe, the posterior quadrant or bifrontal regions). Patient’s mental status was established with the Glasgow Scale score at the time of the selection of the EEG segment. An alert state was considered when the patient could obey commands and/or was oriented. Patients with anoxic CNS insult were excluded from this study. Results: Among the 16 patients (N=9 males and N=7 females) their mean age was 64 years (±15). In 11 patients the continuous video-EEG study was requested because of seizures and in 5 because of altered mental status. Periodicity: among the 16 patients, 7 (44%) had recordings with a periodic and 9 (56%) with a semi-periodic pattern, respectively. An alert state was identified in 14 patients. Of these alert patients, 6 (38%) had a periodic pattern and in 8 (50%) a semiperiodic pattern. Distribution: None of the patients had a generalized or lateralized distribution. In 7 patients (44%) a regional and in 9 (56%) a focal pattern were identified, respectively. In the 14 alert patients, 7 (44%) had a regional and 7 (44%) a focal distribution. In fact all of the patients with a regional pattern and 78% of those with a focal were alert. Localization: was frontal in 5 patients (31%), occipital in 9 (56%), centro-parietal in 1 (6%) and temporal in 1 (6%). Among the 14 alert patients, the EEG pattern was in frontal regions in 3 (21%, and 60% of patients with a frontal localization), in occipital regions in 9 (64% and 100% of patients with an occipital localization), and in centroparietal and temporal regions in 1 (7%), each. Conclusions: These findings suggest that a periodic pattern can be associated with an alert state as long as they have a focal or regional distribution that is independent of the localization. Funding: None