Clinical differences in patients with unilateral hippocampal sclerosis and unitemporal or bitemporal epileptiform discharges.
OBJECTIVE
To investigate factors determining the presence of bilateral interictal epileptiform discharges (IEDs) in temporal lobe epilepsy (TLE) with unilateral hippocampal sclerosis (HS).


METHODS
We analysed data of 243 TLE patients with unilateral HS who had long-term video-EEG. Eighty-one patients (33%) had bitemporal IEDs.


RESULTS
We categorised patients into a unilateral group (UG), a bilateral group (BG) according to presence of bitemporal IEDs. We found no difference between UG and BG regarding epilepsy duration, secondarily generalised seizures, and history of febrile seizures. Mean seizure frequency was significantly higher in the BG (UG: 7.7+/-14.7 seizures/month; BG: 13+/-35 seizures/month, P=0.01). We found a significant correlation between late epilepsy onset and the presence of bitemporal IEDs. The mean age at epilepsy onset in UG was 10.1+/-7.9 years, while in BG it was 13+/-9.2 years (P=0.02).


CONCLUSIONS
The traditional concept of the evolution of mirror focus cannot apply for humans because the duration of epilepsy does not influence the evolution of bitemporal IEDs. Other factors, i.e. age at onset and seizure frequency may play a role in this process. The association between the higher seizure frequency and mirror foci indicates that the development of mirror focus depends on seizures and not on a progressive 'interictal' epileptogenesis.
Janszky
J
J
Epilepsy Center, National Institute of Psychiatry and Neurology, Budapest, Hungary. janszky@index.hu
Rásonyi
G
G
Clemens
Z
Z
Schulz
R
R
Hoppe
M
M
Barsi
P
P
Fogarasi
A
A
Halász
P
P
Ebner
A
A
D000293:Adolescent; D000328:Adult; D016009:Chi-Square Distribution; D004569:Electroencephalography / Q000379:methods; D004833:Epilepsy, Temporal Lobe / Q000473:pathology*; D005260:Female; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012598:Sclerosis / Q000473:pathology; D018709:Statistics, Nonparametric