EEG Abnormalities in Acute Stroke (Ischemic and Hemorrhagic) and Their Prognostic Significance

Abstract

Background: Acute stroke is a serious neurological emergency, and often associated with disturbances in cerebral electrical activity. EEG is able to reveal functional abnormalities of the brain including non-convulsive status epilepticus, electrographic seizures, epileptiform discharges, diffuse slowing and focal slowing that may not be clinically evident. EEG may offer some prognostic information about the severity of the stroke and prognosis, in addition to the role it plays in diagnosis, but neuroimaging is still important for the diagnosis.

Objective: To determine the frequency and pattern of EEG abnormalities in patients with acute ischemic and hemorrhagic stroke and to assess their prognostic significance.

Methods: The study was a prospective, multicenter, observational study that took place from 10 January 2025 to February 2026 in Akbar Niazi Teaching Hospital, Islamabad and Al-Khidmat Raazi Hospital, Rawalpindi. Overall, 385 patients with acute stroke were included of which 275 patients were enrolled from Akbar Niazi Teaching Hospital and 110 patients from Al-Khidmat Raazi Hospital. The diagnosis of stroke was made by clinical examination and imaging. Patients were divided into ischemic stroke group and hemorrhagic stroke group. EEG was obtained in the acute period and was evaluated for background abnormalities, focal slowing, diffuse slowing, epileptiform discharges, periodic discharges, electrographic seizures, and severe EEG abnormalities. The clinical severity was determined by the National Institutes of Health Stroke Scale and Glasgow Coma Scale. The outcomes measured were: admission to the intensive care unit (ICU), mechanical ventilation, hospital stay, functional status at hospital discharge and in-hospital mortality. Data were analyzed with SPSS version 25 and P-values < 0.05 were regarded as statistically significant.

Results: Among 385 patients, 286 (74.3%) had ischemic stroke and 99 (25.7%) had hemorrhagic stroke. EEG abnormalities were observed in 278 patients (72.2%). The most frequent EEG abnormality was focal slowing 169 (43.9%), followed by diffuse slowing 123 (31.9%), reduced background activity 96 (24.9%), epileptiform discharges 64 (16.6%), periodic discharges 39 (10.1%), electrographic seizures 31 (8.1%), and non-convulsive status epilepticus 15 (3.9%). EEG abnormalities were significantly more common in hemorrhagic stroke than ischemic stroke 84.8% vs 67.8%, p = 0.001. Severe EEG abnormalities were significantly associated with severe NIHSS score, low GCS score, ICU admission, mechanical ventilation, prolonged hospital stay, poor functional outcome, and in-hospital mortality.

Conclusion: EEG abnormalities are frequent in acute stroke and are more common in hemorrhagic stroke than ischemic stroke. Severe EEG abnormalities, especially diffuse slowing, epileptiform discharges, periodic discharges, and electrographic seizures, are strongly associated with poor clinical outcomes. EEG may serve as a useful bedside tool for early risk stratification, seizure detection, and prognostic assessment in acute stroke patients.