Superior Frontal Sulcus Focal Cortical Dysplasia Type II: An MRI, PET, and Quantified SEEG Study.

Chao Zhang,Yan-Shan Ma,Aileen Mcgonigal,Kai Zhang,Bao-Tian Zhao,Jian-Guo Zhang,Xiao-Qiu Shao,Wen-Han Hu,Xiu Wang

doi:10.3389/fneur.2019.01253

Abstract

Purpose: The superior frontal sulcus (SFS), located in the prefrontal and premotor cortex, is considered as one of the common locations of focal cortical dysplasia (FCD). However, the characteristics of seizures arising from this area are incompletely known. The primary purpose of this study was to investigate the clinical features and the epileptic networks of seizures originating from the SFS.Methods: We included seventeen patients with type II FCD within the SFS. SFS was identified both visually and automatically. Semiological features were evaluated and grouped. Interictal 18FDG-PET imaging in all patients was compared to controls using statistical parametric mapping (SPM-PET). In those subjects with stereoelectroencephalography (SEEG), two different quantitative intracranial electroencephalography analyses were applied. Finally, the locations of the SFS-related hypometabolic regions and epileptogenic zones (EZs) were transformed into standard space for group analysis.Results: We identified two semiological groups. Group 1 (9/17) showed elementary motor signs (head version and tonic posturing), while group 2 (8/17) exhibited complex motor behavior (fear, hypermotor, and ictal pouting). Based on SPM-PET, an SFS-supplementary motor area (SMA) epileptic propagation network was found in group 1, and an SFS-middle cingulate cortex (MCC)-pregenual anterior cingulate cortex (pACC) propagation network was discovered in group 2. Intracranial EEG analysis suggested similar affected structures with high epileptogenicity. The SFS-related hypometabolic regions and EZs in these groups showed a posterior-anterior spatial relationship.Conclusions: Even though originating from the spatially restricted cortex, SFS seizures can be divided into two groups based on semiological features. The SFS-SMA and SFS-MCC-pACC epileptic propagation networks may play pivotal roles in the generation of different semiologies. The posterior-anterior spatial relationship of both hypometabolic regions and EZs provides potentially useful information for distinguishing different types of SFS seizures and surgical evaluation.

Highlights

Focal cortical dysplasia (FCD) is a common cause of refractory epilepsy [1]
No previous studies have characterized the spectrum of semiology and underlying FCD type II–related epileptic networks centered around the superior frontal sulcus (SFS)
The surgical extent based on the post-surgery CT/MRI and the surgical plan was presented in Supplementary Materials

Summary

Introduction

Focal cortical dysplasia (FCD) is a common cause of refractory epilepsy [1]. Despite high-resolution MRI, FCD may be challenging to detect radiologically; even in MRInegative cases, the epileptogenic zone (EZ) associated with FCD may be localized using stereoelectroencephalography (SEEG) and/or interictal FDG-PET, allowing surgical treatment and good outcome in a high proportion [2]. A recent study has shown that the semiology of frontal lobe seizures can be correlated with the anatomic organizations along with a rostrocaudal axis [5]. The detailed semiological patterns of seizures originating from superior frontal sulcus (SFS) as well as their underlying epileptic networks remain incompletely elucidated, contributing to a non-negligible failure rate in frontal lobe epilepsy surgery, especially for MRI-negative cases [6]. SEEG presents advantages in this scenario, allowing exploration of both superficial and deep frontal structures; the base of a sulcus, a common site for FCD [4], can be readily explored.

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