Abstracts

Rationale: Bisynchronous spike-and-wave activity (BSWA) in generalized epilepsy is attributed to primary bilateral synchrony (PBS), in which cortical areas are activated simultaneously in both hemispheres via ascending subcortical fibers; or to secondary bilateral synchrony (SBS), in which cortical activation in one hemisphere results in secondary activation of the contralateral hemisphere via callosal fibers. SBS is also considered an important mechanism of BSWA in focal frontal lobe epilepsy. However, there is still no established role for PBS in focal epilepsy. Methods: This is a case study of a 23-year-old female with childhood-onset epilepsy. Her first seizure occurred when she was 11 years old. All of her seizures (except for one episode of status epilepticus; see below) were primary generalized tonic-clonic seizures (no focal signs/auras at onset). Absence, myoclonus, and other seizures were ruled out by her mother. Local physicians treated her with phenobarbital for years; zonisamide was added later. She was first seen in our epilepsy clinic two years ago with increasing seizure frequency. Levetiracetam was added and a phenobarbital weaning schedule was initiated. After a two-month seizure-free interval, she developed a frontal-lobe type of complex partial status epilepticus; she was confused and was found wandering on the street. The event lasted 30 minutes and recovery was complete. Because of this unusual event, we reviewed her MRI and EEG records.Results: Two routine EEGs showed infrequent brief (~5 seconds) 3Hz BSWA with maximum spike voltage at F3, Fz, and F4; no behavioral correlate was seen on video. The onset of BSWA was abrupt and simultaneous on both sides. The time difference between the left (F3) and the right (F4) peak spike voltage (phase reversal) ranged from 0 to 8 milliseconds. There is no consistency as to the leading side. These findings indicate that PBS is the mechanism underlying BSWA in this case. EEG also showed intermittent focal delta activity, often bifrontal and symmetric, but occasionally lateralized to the left. Brain MRI showed a round lesion in the right frontal subcortical white matter.Conclusions: BSWA in frontal lobe epilepsy is traditionally attributed to SBS. This case reminds us of the unique nature of epilepsy and demonstrates a possible role for PBS in focal frontal lobe epilepsy.