The Role of the Three-Dimensional Edge-Enhancing Gradient Echo Sequence at 3T MRI in the Detection of Focal Cortical Dysplasia: A Technical Case Report and Literature Review

Abstract

Introduction: Focal cortical dysplasia (FCD) is a most common cause of intractable focal epilepsy in children. Surgery is considered as a radical option for such patients with the prerequisite of lesion detection. Magnetic resonance imaging (MRI) plays a significant role in detection of FCDs in epilepsy patients; however, the detection of FCDs even in epilepsy dedicated MRI sequence shows relatively low positive rate. Last year, Middlebrooks et al introduced the novel three-dimensional Edge-Enhancing Gradient Echo (3D-EDGE) MRI sequence and using this sequence successfully identified five cases of FCDs which indicates its potential role in those epilepsy patients who may have FCDs.

Case presentation: We present a 14-year-old, right-handed, male patient who has suffered from drug-resistant epilepsy over the past 3 years. It was unable to localize the lesion of the seizure, even using the series of epilepsy dedicated MRI sequences. Inspired by the previous report, the lesion of the seizure was successfully targeted by 3D-EDGE sequence. Combined with intraoperative navigation and precisely removed the lesion. He was uneventfully recovered with no signs of cerebral dysfunction and no seizure recurrence 8 months after surgery.

Conclusion: The 3D-EDGE sequences show a higher sensitivity for FCD detection in epilepsy patients compared with a series of epilepsy-dedicated MRI protocols. We confirmed that the study by Middlebrooks et al is of great clinical value. If the findings on routine MRI sequences or even epilepsy-dedicated MRI sequences were reported as negative, however, the semiology, video-electroencephalography, and fluorodeoxyglucose-positron emission tomography results suggest a local abnormality, and the results are concordant with each other, a 3D-EDGE sequence may be a good option.

Fig. 1

Comparison between different MRI sequences ( A–A2 ) transverse, sagittal, and coronal views of MPRAGE, ( B–B2 ) T2-TSE, ( C–C2 ) T2-FLAIR, ( D–D2 ) MP2RAGE, ( E–E2 ) DIR, ( F–F2 ) 3D-EDGE imaging. Subcortical hypointense with a transmantle sign is seen only at the 3D-EDGE sequence (arrows in F–F2 ). Based on the lesions found on 3D-EDGE sequence imaging, reviewed the other MRI sequences carefully, and DIR sequence indicates that there is a subtle fuzzy abnormal signal at the same level of lesions (arrows in E–E2 ). On the FDG-PET, there was extensive hypometabolism in the left parietal lobe area (arrows in G). ( a ), interictal EEG. Note spike waves over the left central-parietal area. ( b ) Ictal EEG associated with myoclonic jerks. 3D-EDGE, three-dimensional edge-enhancing gradient echo; EEG, electroencephalography; FDG-PET, fluorodeoxyglucose–positron emission tomography; FLAIR, fluid-attenuated inversion recovery; MPRAGE, magnetization-prepared rapid acquisition gradient echo MRI, magnetic resonance imaging; MP2RAGE, magnetization-prepared 2 rapid acquisition gradient echo; TSE, transmissible spongiform encephalopathies.

Fig. 2

We choose the right parietal interhemispheric approach to reach the lesion (white arrow B2, C2 ). ( A–A2 ) 3D-EDGE transverse, sagittal and coronal view of the lesion. Postoperative MRI images showed complete resection of the lesion. ( B–B1 ) Postoperative T2-TSE images transverse, sagittal view. ( C–C2, B2 ) Postoperative 3D-EDGE imaging the same level of lesion transverse, sagittal, and coronal view. 3D-EDGE, three-dimensional edge-enhancing gradient echo; MRI, magnetic resonance imaging; TSE, transmissible spongiform encephalopathies.