Abstract Details

Title Epidemiology of Electrographic Periodic and Rhythmic Patterns and Associations with Outcomes: A Multi-center Study

Topic Epilepsy/Clinical Neurophysiology (EEG)

Presentation(s) S41 - Epilepsy: Public Health and Epidemiology (1:36 PM-1:48 PM)

Poster/Presentation
Number 004

Objective To evaluate the frequency, risk factors and prognostic significance of electroencephalographic (EEG) epileptiform activity (EA) in hospitalized adults.

Background Epileptiform activity, encompassing lateralized and generalized periodic discharges (LPDs, GPDs) and rhythmic delta activity (LRDA, GRDA), is frequently identified in acute neurology and critical care patients undergoing continuous EEG (cEEG) monitoring. The full diagnostic and prognostic significance of these patterns is yet to be determined.

Design/Methods We conducted a retrospective cohort study of adults who underwent cEEG monitoring at three centers (2009–2024). Patients with ≥2-hour EEG recordings were included. Clinical data, comorbidities, and diagnoses were extracted from electronic health records using structured ICD codes and natural language processing. Cox proportional hazards models assessed associations between EA and outcomes—90-day and 1-year mortality, and new-onset epilepsy—adjusting for age, sex, Charlson Comorbidity Index, primary diagnosis, and prior epilepsy.

Results Among 29,809 patients (median age 65 years, 54% male), EA or seizures were observed in 25.2%. GPDs (10.5%) and LPDs (6.8%) were the most frequent EA subtypes. EA or seizures were independently associated with increased mortality at 90 days (adjusted hazard ratio [aHR] 1.53, 95% CI 1.44–1.62) and at 1 years (aHR 1.53, 95% CI 1.44–1.62). EA alone showed stronger associations (aHR 1.64 and 1.64, respectively). GPDs conferred the highest mortality risk (90-day aHR 1.99; 1-year aHR 1.92), whereas LRDA was not associated with excess mortality. New-onset epilepsy occurred in 7.3% within 90 days and 14.8% at 5 years, with highest risk among patients with LRDA and structural lesions.

Conclusions Epileptiform activity on EEG is a common finding in hospitalized patients and is associated with increased short- and long-term mortality and potential risk of epilepsy. These findings support the prognostic significance of EA beyond seizures and highlight the need for further studies to guide therapeutic strategies.

Authors/Disclosures
Marjan Sarami, MD PRESENTER	Dr. Sarami has nothing to disclose.
Sahar Zafar, MD	Dr. Zafar has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Springer. Dr. Zafar has received research support from NIH. Dr. Zafar has received personal compensation in the range of $5,000-$9,999 for serving as a Speaker for a lecture with Marinus.
M. B. Westover, MD, PhD (MGH)	Dr. Westover has received personal compensation in the range of $50,000-$99,999 for serving as a Consultant for Beacon Biosignals. Dr. Westover has stock in Beacon Biosignals. The institution of Dr. Westover has received research support from NIH. Dr. Westover has received publishing royalties from a publication relating to health care. Dr. Westover has a non-compensated relationship as a cofounder with Beacon Biosignals that is relevant to AAN interests or activities.
Ayan Mitra, PhD	Dr. Mitra has nothing to disclose.
Akbar Anosh	Akbar Anosh has nothing to disclose.
ali han yaramis, MD	Dr. yaramis has nothing to disclose.
Alexandra M. Tautan, PhD	Ms. Tautan has nothing to disclose.
Shadi Sartipi (Mass General Hospital)	No disclosure on file
Marta Fernandes (Massachusetts General Hospital)	Marta Fernandes has nothing to disclose.

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