To describe the prevalence of electrographic seizures (SZ) and epileptiform abnormalities (EA) in acute ischemic stroke (AIS) and examine its association with outcomes at discharge. 

Continuous EEG (cEEG) is widely used to detect SZ in patients with acute brain injury. However, studies examining prevalence and risk of SZ and EA using cEEG in AIS are limited.

Retrospective chart review identified 94 patients with AIS who underwent cEEG between 1/2018 and 1/2019. Demographics, comorbidities and other relevant clinical factors including NIH stroke scale (NIHSS) and treatment interventions were abstracted. cEEG closest to admission (median 2 days) was reviewed for background, SZ and EA (lateralized and periodic discharges (LPDs and GPDs) lateralized rhythmic delta activity (LRDA) and sporadic epileptiform discharges (sEDs). Computed tomography or magnetic resonance imaging of brain closest to the time of cEEG was analyzed for midline shift, hemorrhagic transformation (HT) and cortical involvement. Outcomes measures were mortality and functional outcome in modified Rankin scale (mRS) (0-2 good and >2 poor outcome) at discharge.

Of the 94 patients, 4 had SZ and 31 had EA (18.1% LPD, 8.5% LRDA, 9.6% GPDs and 3.2% sEDs). Those with cortical involvement had higher rate of EA and Sz compared to those with subcortical stroke (85.3% vs 60.0%, p=0.011). No difference was found in SZ and EA prevalence with regards to age, sex, NIHSS, midline shift or HT. Overall mortality was 29.8%. Absence of posterior dominant rhythm (PDR) was associated with increased mortality (85.7% when PDR absent vs 56.1% when present, p=0.009). SZ and EA did not affect mortality or mRS at discharge.  

Despite high frequency of EA (33%), the risk of SZ in AIS was low at 4.3 % and their presence did not impact functional outcome or mortality. However, EEG background with absence of PDR was associated with increased mortality.