COMPARATIVE LATERALIZING ABILITY of MULTIMODALITY MR IMAGING in TEMPORAL LOBE EPILEPSY ¹ Karabekir Ercan, M.D. ¹ ¹ H.Pinar Gunbey, M.D. ¹ ¹ Elcin Zan, M.D. ¹ ¹ ¹Ataturk Education and Research Hospital, Ankara, Turkey

We have nothing to disclose

Background Temporal lobe epilepsy (TLE) is the most common type of intractable and partial epilepsies predominantly associated with history of febrile convulsions and anterior temporal lobe EEG abnormalities Pathologic analysis shows hippocampal sclerosis in 65% of temporal lobectomy specimens of adults with TLE

The only standard treatment for seizure free status with manifest TLE is surgical; amygdala-hippocampectomy induces recruitment in up to 85% of selected patients Therefore, it is necessary to detect and localize the seizure focus for the best surgical outcome

Comparing the quantitative studies like volumetry, MR spectroscopy, T2 relaxometry and diffusion weighted imaging (DWI) of hippocampus with qualitative ones seems to be relatively objective and can provide more useful information to detect the severity and extent of hippocampal damage

Purpose investigate the comparative lateralizing ability of three quantitative MR (qMRI) modalities; Volumetry, MRS, and DTI patients with electro-clinically diagnosed TLE

Materials and Method Ethical committee approval 14 patients (6F, 8M)with clinical and EEG diagnosis of unilateral TLE 7 left and 7 right TLE Mean age 34.2 years (19-66) 15 healthy volunteers (6F, 9M) 1.5T

For each patient and control; bilateral hippocampal signal intensities, age, duration of epilepsy, interictal EEG lateralization, response to AEDs and history of febrile convulsion were evaluated Seizure free for at least 24 hours prior to MR scan

Volumetry coronal planes were positioned parallel to the PC-OB line

T1-weighted 3D gradient-echo sequence *through 160 slices of the entire brain Hippocampus borders were defined according to procedure of Watson et al and volume calculations obtained with Cavalieri method by multiplying slice thickness with area of hippocampus in each slice To correct the individual differences of each subject head sizes a ratio that was described by Cendes et al and modified by Kalvainen et al was used *(TR = 7.2 ms, TE = 33ms, NSA = 1, FOV = 256 mm, slice thickness 1 mm, gap = 0 mm, flip angle = 8º, matrix = 256x256 pixels)

MR Spectroscopy Single voxel acquisition was acquired in axial plane perpendicular to PC-OB line voxel of interest was placed on hippocampus with sagittal, axial and coronal orientation and was defined 20x20x20 mm for each hippocampus using PRESS sequence* 10 minutes for both hippocampi *TE =144 ms, TR = 2000 ms, NSA = 128

Diffusion Tensor Imaging Single-shot spin-echo echo-planar sequence Diffusion sensitizing gradients were applied simultaneously along 6 non-collinear directions (b= 1000s/mm²) FA and MD values were obtained from the average of these slices 160 contiguous slices were acquired with 1 mm slice thickness and no gap The total acquisition time; 6 minutes and 30 s

Kolmogorv-Smirnov test was used to verify the normal distribution of qMRI value The equality of variances (Levene’s test) and student’s t-tests were used for comparing the means of variables with controls Correlations between values were calculated separately for the ipsilateral and contralateral hippocampus with two-tailed Pearson’s correlation test

Results Right TLELeft TLEHealthy Controls MeanSDMeanSDMeanSD Volume (mm³) Ipsilateral Contralateral NAA/ (Cho+Cr) Ipsilateral Contralateral FA Ipsilateral Contralateral MD Ipsilateral Contralateral

Right TLELeft TLEAll patients Volumetry 57% 85% 71% Spectroscopy 57% 14% 35% DTI 57% 28% 42% Volumetry + Spectroscopy 71% 85% 78% Spectroscopy + DTI 85% 42% 64% DTI + Volumetry 85% 100% 92% Lateralizing ability of q-MR modalities

The qualitative analyses of visual inspection revealed 78% unilateral and 22% bilateral hippocampal atrophy Volumetric analysis on 3D images showed 42% unilateral, 21% bilateral atrophy History of febrile convulsion was associated with ipsilateral increased MD values and reduced NAA/ (Cho+Cr) ratios

Hippocampal atrophy Positive correlation; Duration of epilepsy and decreased FA values No correlation; Age at onset and response to antiepileptic drugs Between q-MRI modalities compared with electro-clinical data

Conclusion Volumetry, MRS and DTI studies provide complementary information of hippocampal pathology For lateralization of epileptogenic focus and pre-operative examination, volumetry-DTI combination (92%) represents maximal accuracy