Diffusion tensor imaging tractography parameters of limbic system bundles in temporal lobe epilepsy patients

To investigate changes in diffusion tensor imaging (DTI) measures in limbic system white matter of patients with temporal lobe epilepsy (TLE) using diffusion tensor tractography.

DTI metrics including fractional anisotropy (FA), λ1, λ2, λ3, and trace (Tr) coefficients were obtained from tractography for bilateral fornix, superior and inferior cingulum fibers in 18 patients and 10 healthy controls. Hippocampal signal-to-noise ratio (SNR) quantitative analysis was performed in order to confirm the magnetic resonance imaging (MRI) hippocampal lesion presence or absence in TLE patients.

Nine patients presented unilateral hippocampal sclerosis (TLE+HS) and nine patients had no signal abnormalities on conventional MRI (TLE-HS). On the ipsilateral seizure side, all three investigated tracts showed significant DTI indices abnormalities in both patient groups when compared with controls, most marked on the inferior cingulum. Contralateral to the seizure side, the three tracts presented significant DTI parameters in only the TLE+HS group when compared with controls.

The DTI abnormalities found in the TLE-HS group may suggest that in the inferior cingulum the structural integrity is more affected than in the fornix or superior cingulum white matter bundles. The eigenvalues taken separately add complementary information to the FA and Tr metrics and may be useful indices in better understanding the architectural reorganization of limbic system tracts in TLE patients without HS.