High risk for seizures following subarachnoid hemorrhage regardless of referral bias

Abstract

Background: To investigate the frequency, predictors, and clinical impact of electrographic seizures in patients with high clinical or radiologic grade non-traumatic subarachnoid hemorrhage (SAH), independent of referral bias.

Methods: We compared rates of electrographic seizures and associated clinical variables and outcomes in patients with high clinical or radiologic grade non-traumatic SAH. Rates of electrographic seizure detection before and after institution of a guideline which made continuous EEG monitoring routine in this population were compared.

Results: Electrographic seizures occurred in 17.6 % of patients monitored expressly because of clinically suspected subclinical seizures. In unselected patients, seizures still occurred in 9.6 % of all cases, and in 8.6 % of cases in which there was no a priori suspicion of seizures. The first seizure detected occurred 5.4 (IQR 2.9-7.3) days after onset of subarachnoid hemorrhage with three of eight patients (37.5 %) having the first recorded seizure more than 48 h following EEG initiation, and 2/8 (25 %) at more than 72 h following EEG initiation. High clinical grade was associated with poor outcome at time of hospital discharge; electrographic seizures were not associated with poor outcome.

Conclusions: Electrographic seizures occur at a relatively high rate in patients with non-traumatic SAH even after accounting for referral bias. The prolonged time to the first detected seizure in this cohort may reflect dynamic clinical features unique to the SAH population.

Conflict of interest statement

Conflict of interest

Kathryn L. O’Connor, M. Brandon Westover, Michael T. Phillips, Nicolae A. Iftimia, Deidre A. Buckley, Christopher S. Ogilvy, Mouhsin M. Shafi, and Eric S. Rosenthal declare that they have no conflict of interest.

Figures

Fig. 1

Patient groups. The total cohort included 69 patients. Prior to instituting routine cEEG monitoring for ischemia detection, 17 patients underwent cEEG monitoring for explicit suspicion for seizure. The remaining 52 patients were monitored as part of a ischemia guideline regardless of suspicion for seizure. Of these 52 patients, medical records reported a suspicion for seizure existed at the time cEEG monitoring for 17 patients. No documented clinical concern for seizure was documented at the time cEEG commenced for the remaining 35 patients monitored under the guideline

Fig. 2

Effect of referral bias on seizure detection rate. The rate of seizure detection is higher among patients with non-traumatic SAH undergoing cEEG monitoring because of suspected subclinical seizures (white bar) versus patients monitored per routine care regardless of suspicion for seizure (black bar). Among patients monitored after institution of ischemia monitoring, patients whose treating physician documented a clinical suspicion for seizure at the commencement of cEEG monitoring (striped bar) had a higher rate of detected seizures than in patients for whom there was no clinical suspicion (dappled bar), though in these latter patients seizure frequency was still high

Fig. 3

Time to seizure detection. Length of cEEG monitoring is shown, ordered by duration of cEEG monitoring. Those patients who developed a seizure are focused on within the inset