Preliminary Study Of The Optic Radiation In Temporal Lobe Epilepsy Using Diffusion Tensor Imaging Based Fiber Tracking

Objective:To explore the validity and accuracy for diffusion tensor imaging(DTI) based fiber tracking(FT) to depict the optic radiation(OR) in temple lobe epilepsy(TLE).Methods:l.The optic radiation in TLE was dipicted by DTI based FT and the extent of visual field defect(VFD) in the same patient was assessed pre-and post-operatively.2. The distances from the anterior edge of Meyer's loop to the temporal pole and the tip of the temporal horn were calculated respectively.3.Fractional anisotropy(FA) of bilateral optic radiations in TLE were calculated.And optic radiation was depicted by DTI according to different FA threshold(0.1,0.2,0.3).Results:1. In all subjects,the optic radiation could be readily identified with DTI based FT,which was consistent with the results of classic anatomical studies. The rate of visual field defects (VFDs) due to optic radiation (OR) injury was 41.7%.4 patients are a contralateral quadrantanopia,and 1 homonymous contralateral VFDs.2. The distance between the most anterior part of Meyer's loop and the temporal pole was 29-42 mm.The distance from the most anterior part of Meyer's loop to the tip of the temporal horn was 3-10mm in 6 patients,0 mm in 2 patients,and Meyer's loop exceeded the tip of the temporal horn by 2 mm in 1 patient.3. The FA value was 0.461±0.028 in the epileptic side and 0.487±0.021 in the normal one.Significant difference was found (P<0.01).Conclusions:1. This study indicates that DTI based FT is a reliable method for operation to visualize the optic radiation.2. Meyer's loop has a considerable variability in its anterior extent.With the help of visualizing the optic radiation, we can make peri-operative individualized surgical plan to protect neurological function.3.We can study the mechanism of epilepsy and lateralize the seizure focus by calculating the FA value of optic radiation.The optimal FA threshold and techniques of DTI need to be further studied to develop the accuracy of DTI.