Evolution of EEG Findings in Patients with Acute Brain Injury.

Background: Increasing use of continuous electroencephalography (cEEG) provides the opportunity to observe temporal trends in EEG patterns during the acute phase of brain injury. These trends have not been extensively documented.

Methods: We conducted a retrospective chart review of patients undergoing cEEG between January 1st and June 30th, 2019, at two academic medical centers. Only patients with acute brain injury having electrographic or electroclinical seizures or epileptic EEG findings on day 1 of monitoring and ≥ 2 calendar days of cEEG were included. The temporal evolution of EEG patterns was depicted as a heatmap.

Results: Of 1356 screened patients, 101 met the study criteria. Clinical acute symptomatic seizures occurred in 30 patients (29.7%) prior to EEG. The median number of days of cEEG was 4 (interquartile range 3-6 days). Among patients with electrographic seizures, status epilepticus, generalized periodic discharges, or sporadic epileptiform discharges, 24.6% had improvement and 54.1% had resolution of epileptic EEG findings by the final day of monitoring. In contrast, 65% of patients with lateralized periodic discharges or lateralized rhythmic delta activity persisted or worsened. Overall, 61.4% (62/101) of patients showed either improvement (19.8%) or resolution (41.6%) of their EEG findings prior to hospital discharge. Of the 36 patients with follow-up EEGs at a median of 4.5 (interquartile range 3-8) months after admission for acute brain injury, 83% (30/36) showed either improvement (1/36; 2.7%) or resolution (29/36; 80.6%).

Conclusions: In patients with acute brain injury, we observed a trend over time toward the normalization of most epileptiform patterns, except for lateralized periodic discharges and lateralized rhythmic delta activity. The clinical significance of this trend as it relates to antiseizure medication treatment and neurologic outcomes warrants further investigation in an independent cohort.