Epilepsy Research (2015) 110, 95—104 jo ur nal ho me p ag e: www.elsevier.com/locate/epilepsyres Diffusion tensor imaging tractography of Meyer’s loop in planning resective surgery for drug-resistant temporal lobe epilepsy Jija S. James b , Ashalatha Radhakrishnan a,* , Bejoy Thomas b , Mini Madhusoodanan a , Chandrashekharan Kesavadas b , Mathew Abraham a , Ramshekhar Menon a , Chaturbhuj Rathore a , George Vilanilam a a R Madhavan Nayar Centre for Comprehensive Epilepsy Care, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum 695011, India b Department of Imaging and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum 695011, India Received 13 August 2014; received in revised form 9 November 2014; accepted 19 November 2014 Available online 27 November 2014 KEYWORDS Meyer’s loop; Visual field defect; DTIT; Temporal lobe epilepsy; Optic radiation; Anterior temporal lobectomy Summary Purpose: Whether Meyer’s loop (ML) tracking using diffusion tensor imaging tractography (DTIT) can be utilized to avoid post-operative visual field deficits (VFD) after anterior temporal lobec- tomy (ATL) for drug-resistant temporal lobe epilepsy (TLE) using a large cohort of controls and patients. Also, we wanted to create a normative atlas of ML in normal population. Methods: DTIT was used to study ML in 75 healthy subjects and 25 patients with and without VFD following ATL. 1.5 T MRI echo-planar DTI sequences with DTI data were processed in Nordic ICE using a probabilistic method; a multiple region of interest technique was used for reconstruction of optic radiation trajectory. Visual fields were assessed in patients pre- and post-operatively. Results: Results of ANOVA showed that the left ML-TP distance was less than right across all groups (p = 0.01). The average distance of ML from left temporal pole was 37.44 ± 4.7 mm (range: 32.2—46.6 mm) and from right temporal pole 39.08 ± 4.9 mm (range: 34.3—49.7 mm). Average distance of left and right temporal pole to tip of temporal horn was 28.32 ± 2.03 mm (range: 26.4—32.8 mm) and was 28.92 ± 2.09 mm, respectively (range: 25.9—33.3 mm). If the anterior limit of the Meyer’s loop was ≤38 mm on the right and ≤35 mm on the left from the temporal pole, they are at a greater risk of developing VFDs. ∗ Corresponding author. Tel.: +91 471 2524282; fax: +91 471 2446433. E-mail address: drashalatha@sctimst.ac.in (A. Radhakrishnan). http://dx.doi.org/10.1016/j.eplepsyres.2014.11.020 0920-1211/© 2014 Elsevier B.V. All rights reserved.