Prediction of Laterality in Temporal Lobe Epilepsy Using White Matter Diffusion Metrics

Diagnostic methods of the epileptogenic area continue to be a challenge in epilepsy surgery research. We hypothesized that temporal lobe epilepsy (TLE) will result in white matter changes that can be detected using diffusion tensor imaging. Measurement of white matter diffusivity will therefore be useful for presurgical assessment.

Twelve patients with TLE who had undergone temporal lobectomy and amygdalohippocampectomy were included. In 6 patients, magnetic resonance imaging (MRI) showed evidence of mesial temporal sclerosis (m-TLE), whereas the 6 remaining MRI studies were informed without any abnormality (nl-TLE). All had excellent outcomes from surgery. Patients were compared with 12 age- and sex-matched controls. Five pairs of white matter fiber tracts were traced, and fiber tract fractional anisotropy and mean diffusivity were calculated.

There were several alterations in diffusion parameters in white matter tracts, both ipsilateral and on the contralateral side, these alterations were more pronounced in the hemisphere ipsilateral to the epileptogenic focus. m-TLE patients had more alterations on ipsilateral side than nl-TLE patients, but similar alterations on contralateral side and bilateral fornix. The discriminant function analysis successfully lateralized all the patients with left TLE, 83.3% of the patients with right TLE, and all nl-TLE.

Our results suggest that there are alterations in diffusion parameters in white matter tracts both in m-TLE and nl-TLE patients. Diffusion tensor imaging could be a useful presurgical tool to help establish the laterality of TLE, including patients with "normal" MRI. Further studies with a larger number of patients would be necessary to confirm these results.