Clinical and neuroimaging characteristics in patients with secondary bilateral synchrony (SBS) on EEG

ABSTRACT

RATIONAELE Secondary bilateral synchrony(SBS) is not an unusual finding to the EEGers, but its Significance is not well-delineated. We reviewed the clinical EEG, and neuroimaging characteristicts in patients with SBS. METHOD: Patients who were admitted for presurgical evaluation of intractable epilepsy were classified on the basis of video-EEG monitoring, prolonged interictal EEG, MRI, ictal SPECT, PET, and, in a few cases, the surgical results. We analyzed clinical, electrophysiological, and neuroimaging characteristics of patients with SBS by comparing them, with those without SBS. RESULTS: Among 319 patients who were admitted for presurgical epilepsy evaluation, 26 patients had SBS(8.2%). Medial temporal lobe epilepsy was predominant as a whole(140/319, 43.9%), but frontal lobe epilepsy(FLE) was main syndrome in the SBS group(16/26, 61.5%). Multifocal irritative zones were present in 12.5% of FLE with SBS group(2/16) and in 4.8% of FLE without SBS group(2/42). In FLE with SBS group, the location of ictal onset zone was parasaggital in 32%(5/16) and multifocal in 37%(6/16). There was a tendency to develop secondary generalized tonic clonic seizure in FLE with SBS group than in FLE without SBS group. Neuroimaging modalities revealed frontal abnormalities more accurately in FLE with SBS group than in FLE without SBS group. CONCLUSION: Frontal lobe as an epileptogenic zone is an important factor in generating SBS and SBS seems to facilitate seizure spreading to the contralateral hemisphere.