7T MRI in epilepsy patients with previously normal clinical MRI exams compared against healthy controls

Abstract

ObjectiveTo compare by 7 Tesla (7T) magnetic resonance imaging (MRI) in patients with focal epilepsy who have non-lesional clinical MRI scans with healthy controls.Methods37 patients with focal epilepsy, based on clinical and electroencephalogram (EEG) data, with non-lesional MRIs at clinical field strengths and 21 healthy controls were recruited for the 7T imaging study. The MRI protocol consisted of high resolution T1-weighted, T2-weighted and susceptibility weighted imaging sequences of the entire cortex. The images were read by two neuroradiologists, who were initially blind to clinical data, and then reviewed a second time with knowledge of the seizure onset zone.ResultsA total of 25 patients had findings with epileptogenic potential. In five patients these were definitely related to their epilepsy, confirmed through surgical intervention, in three they co-localized to the suspected seizure onset zone and likely caused the seizures. In seven patients the imaging findings co-localized to the suspected seizure onset zone but were not the definitive cause, and ten had cortical lesions with epileptogenic potential that did not localize to the suspected seizure onset zone. There were multiple other findings of uncertain significance found in both epilepsy patients and healthy controls. The susceptibility weighted imaging sequence was instrumental in guiding more targeted inspection of the other structural images and aiding in the identification of cortical lesions.SignificanceInformation revealed by the improved resolution and enhanced contrast provided by 7T imaging is valuable in noninvasive identification of lesions in epilepsy patients who are non-lesional at clinical field strengths.

Value of 7T MRI and post‐processing in patients with nonlesional 3T MRI undergoing epilepsy presurgical evaluation

“…Because of the higher sensitivity of the 7Ts to blood products (particularly with T2*-weighted GRE and SWI sequences), vascular malformations were shown to be better imaged. 7,11 In our study, this advantage of 7T led to a previously unseen vascular malformation (P6, details in Appendix S2). The definition of "nonlesional" or "negative" 3T MRI has long been the debate in the literature, which largely depends on the experience of the MRI reviewer and the information provided for the review.…”

“…These results suggest that the presence of a lesion on 7T could perhaps be a positive predictor of the presurgical evaluation success, which is of particular importance when 3T MRI is negative. Our current study contributes significantly to the literature [4][5][6][7][8][9][10][11][12]32 because: (a) it included a larger number of patients to address the relationship between 7T MRI findings and ICEEG ictal onset, histopathology as well as postoperative seizure outcomes; and (b) the use of 7T MRI post-processing to guide 7T visual review was investigated for the first time.…”

Establishing criteria for pediatric epilepsy surgery center levels of care: Report from the ILAE Pediatric Epilepsy Surgery Task Force

“…It is unclear what role 7-T MRI or postprocessing image algorithms will assume in the future, as well as technology yet to be developed. [33][34][35] There will be exceptions and differences of view in implementing these standards. For example, cavernomas may be multifocal, whereas a younger child may have a clearly distinct lesion outside of eloquent cortex.…”

Emerging Use of Ultra-High-Field 7T MRI in the Study of Intracranial Vascularity: State of the Field and Future Directions

“…32 In a series of 37 patients with epilepsy with various etiologies who had negative findings on MR imaging at a lower field strength, small cavernomas were identified in 3 patients, 2 of which were likely related to epileptogenesis. 33 Developmental venous anomalies were detected in 4 other patients using 7T SWI, 2 of which coincided with regions of electrographic abnormality, suggesting possible occult cavernomas. 33 In another study of 11 patients with epilepsy with negative findings on MR imaging, 1 patient's diagnosis changed from suspected focal cortical dysplasia to cavernoma based on 7T SWI.…”

“…33 Developmental venous anomalies were detected in 4 other patients using 7T SWI, 2 of which coincided with regions of electrographic abnormality, suggesting possible occult cavernomas. 33 In another study of 11 patients with epilepsy with negative findings on MR imaging, 1 patient's diagnosis changed from suspected focal cortical dysplasia to cavernoma based on 7T SWI. 34 While these studies provide compelling evidence to support the use of 7T in vascular epilepsy imaging, no study has directly compared cavernoma detectability between 3T and 7T SWI.…”