Abstracts

Approximately 40% of patients with medically refractory non-lesional Temporal Lobe Epilepsy (TLE) are not lateralised with current structural MRI techniques including volumetric analysis and T2 mapping. Diffusion tensor (DT) MRI is a relatively new MRI technology that has potential to detect functional abnormalities in patients with normal structural MRI.
[italic]Aims:[/italic] To perform a pilot study to assess the potential for DT MRI to lateralise non-lesional TLE. Seven patients with non-lesional TLE (four with hippocampal sclerosis (HS) and four without HS on structural MRI), and well lateralised seizures on ictal-EEG were studied with DT MRI (1.5 Tesla, GE system) performed in 25 directions with b value: 1500 s/mm[sup2]. The tensor signal was quantitated for voxels placed over the hippocampus and anterior temporal pole bilaterally and the side-to-side ratios correlated with the ictal EEG lateralisation. The tensor signal was higher on the epileptogenic side for the hippocampal voxels in 4/7 (71%) of patients, and for the anterior temporal voxels in 4/7 (51%) of patients. Fractional anisotropy shows a trend to be decreased in the hippocampus ipsilateral to the EEG lateralization. Quantitation of ADC with DT signal in the hippocampal region shows promise for lateralising non-lesional TLE in this pilot study, but further patients and correlation with surgical outcome is required before its role is established