Abstracts

Rationale: Following the placement of intracranial electrodes during phase II EEG monitoring for presurgical evaluation, antiepileptic drugs (AEDs) are discontinued to facilitate the emergence of seizures. While the AEDs are tapered off rapidly in some centers, medications are withdrawn gradually at other hospitals. It is currently unknown, whether either approach leads to higher incidence of seizure clusters (SC) or status epilepticus (SE) during the intracranial EEG (IEEG) monitoring. In the present study we assessed the rates of seizure clusters and status epilepticus in patients undergoing AED withdrawal during the IEEG prior to epilepsy surgery. Methods: Retrospective chart review and analysis of all adult patients who completed IEEG during presurgical evaluation in 2012-2018 was performed to collect demographic information, clinical seizure characteristics and EEG data. The proportions of patients who had at least one SC or an episode of SE during the IEEG monitoring period were calculated. Seizure cluster (SC) was defined as three or more seizures within a 24‐h period, with a return to baseline between seizures. Status epilepticus (SE) was defined as ≥5 min of continuous clinical seizure, ≥ 10 min of ictal electrographic activity or series of seizures in between which there was no return to the neurological baseline. Results: We identified 87 patients who completed IEEG; there were 39 (45%) male and 48 (55%) female. Median age at the time of IEEG was 35 years (range 24-46). Sixty-six patients (83 %) developed SC while 11 patients (17%) developed SE. Of these patients 36 (58%) required intravenous lorazepam or other rescue anticonvulsants while 26 (42%) had spontaneous resolution of seizures. The median number of home AEDs were the same in both groups. Sixty-seven patients (79 %) had all their AEDs held on admission while 18 patients (21%) were continuing to receive at least one anticonvulsant. There was no difference in the proportion of patients with SCs or SE between the groups of patients who had all their AEDs withdrawn on admission compared to those who remain on at least one AED (p = 0.88 and 0.69, respectively; Pearson’s chi-squared test). Conclusions: We found that the rates of SC and SE in patients undergoing IEEG monitoring and AED discontinuation is higher compared to those previously reported to accompany noninvasive EEG. The acute cessation of all AED leads to seizure clustering in more than 70% of patients; however, seizures subside spontaneously in nearly 40% of these patients. The rapid and more gradual cessation of AED precipitates similar rates of SC and SE. Funding: No funding