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Preoperative automated fiber quantification predicts postoperative seizure outcome in temporal lobe epilepsy

Research output: Contribution to journalArticle

Simon S Keller, G Russell Glenn, Bernd Weber, Barbara A. K. Kreilkamp, Jens H Jensen, Joseph A Helpern, Jan Wagner, Gareth J. Barker, Mark P. Richardson, Leonardo Bonilha

Original languageEnglish
Pages (from-to)68-82
Number of pages15
JournalBrain : a journal of neurology
Issue number1
Early online date15 Nov 2016
Publication statusPublished - Jan 2017


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    his is a copy of the Version of Record of an article published in Brain, Volume 140, Issue 1, 1 January 2017 and made available for Open Access via Oxford Open. It is also available online at:

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Approximately one in every two patients with pharmacoresistant temporal lobe epilepsy (TLE) will not be rendered completely seizure free after temporal lobe surgery. The reasons for this are unknown and are likely to be multifactorial. Quantitative volumetric MRI techniques have provided limited insight into the causes of persistent postoperative seizures in patients with TLEtemporal lobe epilepsy. The relationship between postoperative outcome and preoperative pathology of white matter tracts, which constitute crucial components of epileptogenic networks, is unknown. We investigated regional tissue characteristics of preoperative temporal lobe white matter tracts known to be important in the generation and propagation of temporal lobe seizures in TLE, using diffusion tensor imaging (DTI) and Automated Fiber Quantification (AFQ). We studied 43 patients with mesial TLE temporal lobe epilepsy associated with hippocampal sclerosis and 44 healthy controls. Patients underwent preoperative DTIimaging, amygdalohippocampectomy and postoperative assessment using the International League Against Epilepsy seizure outcome scale. From preoperative DTIimaging, the fimbria-fornix (FF), parahippocampal parahippocampal white matter bundle white matter bundle (PWMB) and uncinate fasciculus (UF) were reconstructed using AFQ, and scalar diffusion metrics were calculated along the length of each tract. 51.2% of patients were rendered completely seizure free (ILAE 1) and 48.8% continued to experience postoperative seizure symptoms (ILAE 2-5). Relative to controls, both patient groups exhibited strong and significant diffusion abnormalities along the length of the UF uncinate bilaterally, the ipsilateral PWMBparahippocampal white matter bundle, and the ipsilateral FF fimbria-fornix in regions located within the medial temporal lobe. However, only patients with persistent postoperative seizures showed evidence of significant pathology of tract sections located in the ipsilateral dorsal fornix and in the contralateral PWMBparahippocampal white matter bundle. Using receiver operating characteristic (ROC) curves, diffusion characteristics of these regions could classify individual patients according to outcome with 84% sensitivity and 89% specificity. Pathological changes in the dorsal fornix were beyond the margins of resection, and contralateral PWMB parahippocampal changes may suggest a bi-temporal disorder in some patients. Furthermore, diffusion characteristics of the ipsilateral UF uncinate could classify patients from controls with a sensitivity of 98%; importantly, by co-registering the preoperative AFQ fiber maps to postoperative surgical lacuna maps, we observed that the extent of UF uncinate resection was significantly greater in patients who were rendered seizure free, suggesting that a smaller resection of the UF uncinate may represent insufficient disconnection of an anterior temporal epileptogenic network. These results may have the potential to be developed into imaging prognostic markers of postoperative outcome and provide new insights for why some patients with TLE temporal lobe epilepsy continue to experience postoperative seizures

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