Abstracts

Rationale: Diffusion Tension MR Imaging (DTI ) studies of temporal lobe epilepsy (TLE) have evidenced white matter tract (WMT) abnormalities that extend beyond the temporal lobe. Associations between TLE and volumetric abnormalities in several brain structures have also been described. It is unknown if inter or ictal epileptiform discharges contralateral to the structural lesion are associated with more extensive ipsi or contralateral WMT or volumetric abnormalities. On this study, we evaluated the relation between contralateral epileptiform discharges and tract integrity in ipsi and contralateral hemispheres in patients with unilateral mesial tempora sclerosis (uMTS). Methods: Consecutive patient series of patients with TLE (associated with uMTS) who underwent an MRI protocol including DTI, also studied with videoelectroencephalographic monitoring. Patients were classified according to ictal and interictal EEG findings as Concordant (Co) ?" more than 70% interictal discharges and ictal EEG activity restricted to the MTS side or Discordant (Di) ?" less than 70% interictal discharges or independent ictal involvement on the contralateral side. MRI DTI data were analyzed with tract based spatial statistics (TBSS). Corpus Callosum (CC) volumetry was analysed with FreeSurfer. We compared fractionated anisotropy (FA) of 8 ipsi and contralateral WMT, 2 interhemispheric WMT and CC volumetry for Co, Di groups and controls using ANOVA and post-hoc tests with p < 0.01. Results: Results and conclusion: We studied 51 patients: 19 Co (37.3%) 32 Di (63.8%) and 29 healthy controls. Groups did not differ in age (mean 34 years), gender (43.2% women) and epilepsy duration (mean 22+/- years). We found decreased FA in four ipsilateral structures (anterior thalamic radiation, cingulate gyrus, inferior fronto-occipital, inferior and superior longitudinal fasciculi) in the Di group, but not in the Co, compared to C. We also found involvement of four interhemipheric structures (forceps minor, mid-anterior, central and mid-posterior CC regions) in the Di group, but not in the Co group, compared to C. This pattern was not observed in contralateral tracts. In two ipsilateral and two contralateral WMT, both patient groups differed from controls. We found no differences in WMT integrity comparing Di and Co groups. Conclusions: Interictal and ictal activity contralateral to the MTS side was associated with more extensive ipsilateral temporo-limbic and extratemporal WMT damage and, more pronouncedly,in interhemispheric connecting fibers, specially in mid-callosal portions. Funding: FAPESP- Sao Paulo Research foundation (Process 2005/56464-9) FAPESP Bolsa de Inicia磯 Cient_x005F_xD9A9_ca (AQC)