Abstracts

Rationale: Antiepileptic drugs (AEDs) are discontinued during epilepsy monitoring unit (EMU) studies in an attempt to precipitate seizures. Some AEDs, such as oxcarbazepine and carbamazepine, need to be slowly withdrawn as they can cause severe withdrawal seizures. Levetiracetam (LEV) and lamotrigine (LTG) are commonly used AEDs that are also routinely discontinued during EMU studies. The aim of this study is to evaluate the severity and temporal pattern of LTG and LEV withdrawal seizures during epilepsy monitoring. Methods: We identified all patients with epilepsy who were admitted to the Vanderbilt EMU and were on LEV monotherapy, LTG monotherapy or combination LEV and LTG therapy over the last five years. We only included patients who had their AED of interest abruptly discontinued on EMU admission day and patients who had complex partial seizures (CPS) or generalized tonic-clonic seizures (GTC). For each patient, we recorded pre-EMU seizure types and frequency. We noted age, gender, epilepsy onset, epilepsy risk factors, AED total dose and blood levels. We then recorded the number and type of seizures for each EMU day. We compared the seizure frequency before and during EMU for each seizure type. We also compared the first seizure (any seizure, CPS or GTC) occurrence during EMU between the three groups. Results: A total of 69 patients (45 females) were included in the study. Twenty eight patients were on LEV monotherapy, 10 patients on LTG monotherapy, and the remaining 31 patients were on combination therapy. For all groups, the mean age was 35.9 15.4 years, mean LEV dose was 2148 989 mg and mean LTG dose was 290 129 mg. Mean blood levels were within the accepted therapeutic range. There was no difference in pre-EMU CPS and GTC frequency, age at onset, or epilepsy risk factors among the three groups. The average EMU stay was 3.9 2.1 days. CPS and GTC during EMU were higher than pre-EMU baseline in all groups (p<0.05, Wilcoxon signed rank test). Total CPS during EMU tended to be higher than total GTC. No first time GTC during EMU was reported in 27 patients with no prior history of GTC. In addition, none of the patients had reported status epilepticus. The mean time to first CPS during EMU was 1.9 0.9 days while that of GTC was 2.1 1.1 days. Time for first CPS after LTG withdrawal was the longest compared to the other two groups (p=0.03, log-rank test). Conclusions: Acute discontinuation of LEV or LTG is not associated with severe withdrawal seizures. Withdrawal seizures occur approximately 48 hours following discontinuation. This suggests that LEV or LTG may be safely discontinued 24 hours prior to EMU admission. This approach may help in reducing hospital stay and cost.