Epileptiform abnormalities predict delayed cerebral ischemia in subarachnoid hemorrhage

Abstract

Objective To identify whether abnormal neural activity, in the form of epileptiform discharges and rhythmic or periodic activity, which we term here ictal-interictal continuum abnormalities (IICAs), are associated with delayed cerebral ischemia (DCI). Methods Retrospective analysis of continuous electroencephalography (cEEG) reports and medical records from 124 patients with moderate to severe grade subarachnoid hemorrhage (SAH). We identified daily occurrence of seizures and IICAs. Using survival analysis methods, we estimated the cumulative probability of IICA onset time for patients with and without delayed cerebral ischemia (DCI). Results Our data suggest the presence of IICAs indeed increases the risk of developing DCI, especially when they begin several days after the onset of SAH. We found that all IICA types except generalized rhythmic delta activity occur more commonly in patients who develop DCI. In particular, IICAs that begin later in hospitalization correlate with increased risk of DCI. Conclusions Thus, IICAs represent a new marker for identifying early patients at increased risk for DCI. Moreover, IICAs might contribute mechanistically to DCI and therefore represent a new potential target for intervention to prevent secondary cerebral injury following SAH. Significance These findings imply that IICAs may be a novel marker for predicting those at higher risk for DCI development.

Effect of epileptiform abnormality burden on neurologic outcome and antiepileptic drug management after subarachnoid hemorrhage

“…DCI was significantly more common in patients with EA (65.1%) vs. those without (35.2%, p=0.001). This finding was also demonstrated in our prior work showing that the emergence of periodic discharges, epileptiform activity and lateralized rhythmic delta activity predict DCI (Kim et al ., 2017). …”

“…The overall EA exposure or burden over the entire course of cEEG monitoring does not have a standardized definition. We therefore examined three alternative formulations as quantitative markers of the overall EA burden for each patient: Presence: presence of any EAs within any epoch; First day burden : burden within the first 18–24 hour epoch; Maximum daily burden : maximum EA burden within any 18–24 hour epoch. As GRDA is a more benign pattern, with minimal association with both seizures and DCI (Kim et al ., 2017; Ruiz et al ., 2017; Struck et al ., 2017), we excluded isolated GRDA, including isolated GRDA with plus features when evaluating EA burden calculations. We also excluded isolated GRDA with plus features as it has a lower association with seizures (Ruiz et al ., 2017).…”

Electroencephalography, Hospital Complications, and Longitudinal Outcomes After Subarachnoid Hemorrhage

“…In this cohort of nontraumatic SAH patients with high clinical or radiologic grade, cEEG abnormalities have a differential association with functional outcome. While both have previously been shown to predict DCI [ 4 , 5 ], our results suggest that only new or worsening EAs appear to have a strong, durable association with outcome measured by the modified Rankin Scale, similar to that for DCI itself. By demonstrating that background deterioration lacks this association and that a worsening in EA burden may influence recovery more than other hospital complications such as HAI, hydrocephalus, or the rare occurrence of aneurysmal rebleeding, our results build upon prior findings linking EA burden to poor outcome following SAH [ 5 ]…”

“…These results may help elucidate potential mechanisms contributing to DCI, a dangerous complication following SAH [ 26 ]. Neurophysiologic changes have previously been proposed as one pathway contributing to DCI progression [ 27 ] and new or worsening EAs are representative of poor cerebral metabolism [ 9 – 12 ] and have been shown to predict DCI [ 4 , 5 ]. Furthermore, these EEG abnormalities have previously been linked to cortical spreading depolarizations [ 10 – 12 ], which themselves have been associated with DCI and subsequent poor outcome [ 13 , 28 , 29 ].…”

Ictal-Interictal Continuum: When to Worry About the Continuous Electroencephalography Pattern

“…33 In addition to the increased risk of seizures, recent work has shown that LPDs may be predictive of delayed cerebral ischemia in patients with aneurysmal subarachnoid hemorrhage (aSAH), although it is unclear if they are mechanistically involved, predictive markers, or merely disease bystanders. 44 While the association between LPDs and seizure risk is well-accepted, a more controversial theory is that LPDs may themselves be an ictal phenomenon. Some groups argue that LPDs are considered ictal in cases where stereotypic focal movements-such as in focal motor seizures or epilepsia partialis continua-are time-locked to discharges.…”