The role of ultra-high field MRI and image processing in the presurgical workup in MRI-negative focal epilepsy: A validated 7T MRI case study

Abstract

This case study demonstrates the value of combined 7 T structural and functional MRI in the presurgical workup of a 24-year-old male with drug-resistant focal epilepsy who was initially considered MRI-negative on clinical 3 T MRI. The patient underwent extensive presurgical workup with 7 T MRI, magnetoencephalography, stereo-electroencephalography, and resection of the suspected right frontal epileptogenic zone. Histopathology showed focal cortical dysplasia (FCD) type IIb. The patient remained 11 months after surgery seizure-free. Retrospective analysis revealed that both structural and functional 7 T MRI showed abnormalities within the resected area. Morphometric Analysis Program (MAP18) detected abnormalities on both 3 T and 7 T images. However, abnormalities were more conspicuous on 7 T. Resting-state functional MRI metrics, particularly regional homogeneity and fractional amplitude of low-frequency fluctuations, demonstrated significantly increased values in both a MAP18-defined region of interest and the entire resected area compared to a healthy control group (p < 0.05). However, extensive unspecific abnormalities were also observed outside the resected region, highlighting the importance of a multimodal approach. This case study illustrates that advanced image processing of ultra-high field structural and resting-state functional MRI scans may enhance the detection of subtle epileptogenic lesions in presurgical evaluation, potentially improving post-operative seizure outcome and associated quality of life.

Keywords

• 7T MRI
• Focal cortical dysplasia
• Resting-state fMRI
• Voxel-based morphometry
• ReHo
• fALFF