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Front. Neurol. | doi: 10.3389/fneur.2018.00106

Small lesion size is associated with sleep-related epilepsy in focal cortical dysplasia type II

Bo Jin1,  Wenhan Hu2, Balu Krishnan3,  Thandar Aung3,  Stephen E Jones4,  Imad M Najm3, Andreas V Alexopoulos3, Kai Zhang2, Junming Zhu5,  Jianguo Zhang2, Meiping Ding1, Zhong Chen1, 6,  Shuang Wang1* and  Zhong Irene Wang3
  • 1Department of Neurology, Epilepsy Center, Second Affiliated Hospital of Zhejiang University School of Medicine, China
  • 2Department of Neurosurgery, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, China
  • 3Epilepsy Center, Cleveland Clinic, United States
  • 4Department of Diagnostic Radiology, Mellen Imaging Center, Cleveland Clinic, United States
  • 5Department of Neurosurgery, Epilepsy Center, Second Affiliated Hospital of Zhejiang University School of Medicine, China
  • 6Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, China

Objective: To investigate the neuroimaging and clinical features associated with sleep related epilepsy (SRE) in patients with focal cortical dysplasia (FCD) type II.
Methods: Patients with histopathologically proven FCD type II were included from three epilepsy centers. SRE was defined according to the video-EEG findings and seizure history. Cortical surface reconstruction and volume calculation were performed using FreeSurfer. The lesions were manually delineated on T1 volumetric MRI using the ITK-SNAP software. The lesion volumes were normalized by the intracranial volume of each patient. The lesions were classified as small or large by placing a threshold based on quantitative (whether the lesion was detected on MRI report) and qualitative (volume) criteria.
Results: A total of 77 consecutive patients were included. Of them, 36 had SRE and 41 had non-SRE. An earlier age of epilepsy onset, high seizure frequency, regional interictal EEG findings and favorable surgical outcome were characteristic in both groups. Small lesions were defined as those having a volume < 3217 mm3. In total, 60.9% of the patients with SRE (25/41) had small FCD lesion, which was significantly higher than the non-SRE group (9/34, 26.5%, p=0.005). Small lesion size was the only predictor significantly associated with SRE in the overall type II group by multivariate analyses (p=0.016). Although the proportion of patients who had frontal FCD and SRE was higher than non-frontal FCD (54.5% vs. 27.3%, p=0.043), the relationship between SRE and lesion location was not confirmed by multivariate analysis. Thalamic volume and seizure semiology were not statistically different between the SRE and non-SRE group. The significant association between lesion size and SRE was reproducible in type IIb and IIa subgroups.
Significance: SRE is common in patients with FCD type II. Small FCD type II lesions are significantly associated with SRE. Although our findings cannot be applied to the entire spectrum of SRE, potential existence of small FCD lesions should be considered when evaluating patients with SRE, and utilization of all other supportive electroclinical information for lesion detection is highly desirable.

Keywords: Focal cortical dysplasia type II, Sleep-related epilepsy, MRI, volume, location

Received: 11 Oct 2017; Accepted: 13 Feb 2018.

Edited by:

Fernando Cendes, Universidade Estadual de Campinas, Brazil

Reviewed by:

Marino M. Bianchin, Federal University of Rio Grande do Sul (UFRGS), Brazil
Luca Bartolini, National Institute of Neurological Disorders and Stroke - NINDS (NIH), United States  

Copyright: © 2018 Jin, Hu, Krishnan, Aung, Jones, Najm, Alexopoulos, Zhang, Zhu, Zhang, Ding, Chen, Wang and Wang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Shuang Wang, Second Affiliated Hospital of Zhejiang University School of Medicine, Department of Neurology, Epilepsy Center, Hangzhou, China, shuangwang1977@gmail.com