Abstracts

Rationale: The rate of interictal epileptiform discharges (IEDs) in patients with focal epilepsy does not appear to be influenced by drug levels. The rate of spiking does not increase prior to seizures but increases markedly after them (Gotman & Marciani - Annals of Neurology 1985). The relation between IEDs, drug levels and seizures has been less well documented in patients with generalized epilepsy. Methods: We report the case of a patient with presumed idiopathic generalized epilepsy monitored for 99 hours during a 4 day admission at IU Epilepsy Monitoring Unit. This was an18 year old woman with borderline intellectual functioning (full scale IQ of 70) who experienced generalized tonic clonic seizures (GTCs) without auras. She was diagnosed with epilepsy at age 15. She experienced occasional nocturnal seizures few years prior. The patient experienced staring spells of up to a minute duration twice per year. Her general and neurological examinations as well as brain MRI were normal. Outpatient EEG showed no IEDs. The patient was admitted for pre-surgical evaluation with a presumed diagnosis of localization related epilepsy. At the time, the patient was treated with levetiracetam, lacosamide and oxcarbazepine. The levetiracetam and lacosamide were reduced to half dose on day one and stopped on day two. The oxcarbazepine was reduced to half dose on day two. A GTC was recorded on day four. Electrographic onset consisted of generalized spike and wave discharges. This was classified as a generalized seizure by the IU Epilepsy Surgery Committee. Immediately after the seizure, the patient received lorazepam and her home anti-seizure medications were restarted. The patient was monitored for an additional 28 hours. Results: The IEDs were characterized as irregular generalized spike wave discharges often in bursts. The IEDs were manually marked and counted. The first IED occurred 60 hours into the recording, less than 12 hours prior to the GTC. In the 12 hours interval preceding the GTC we counted 12 IEDs for the first 6 hours (maximum burst duration: 2.5-3 sec), and 213 IEDs in the 6 hours immediately preceding the GTC (maximum burst duration: 4.5-5 sec). We counted a single IED (duration - less than 1sec) in the postictal recording, which occurred 4 hours after the GTC. Conclusions: In this patient with generalized epilepsy and baseline EEG without IEDs, there was a dramatic increase of IEDs in the 12 hours prior to a GTC and a dramatic decrease postictally. This could have been a result of medication level changes and/or the effect of the seizure itself. This appears to be the opposite of what has been reported for patients with localization related epilepsy. Further prospective studies will help determine if this phenomenon is characteristic for patients with generalized epilepsy. This could have implications in seizure prediction methods for these patients.