Figures
Figure 1
Example illustrating the importance of inspecting all imaging planes: coronal, axial and sagittal. In the left anterior insular region, highlighted by the crosshair, a focal area of gray matter appears to have a blurred appearance on the axial cut. However, when examining the coronal and sagittal planes, it is evident that this finding was produced by an axial slice catching the upper portion of the insular cortex. The blurred appearance was thus caused by the combined “averaging” of signal changes from both gray and white matter tissue (partial volume effect).
Figure 1
Figure 2
A small FCD in the right frontal lobe (arrows) illustrated with T1-weighted MPRAGE (left), T2-weighted (T2-w) TSE (middle) and T2-weighted FLAIR (right) images. Upper row: images with default brightness and contrast from the picture archiving and communication system (PACS) viewing system. Lower row: adjusting the image brightness and contrast enhances the conspicuity of the transmantle sign within the white matter. Note that the transmantle sign is mainly visible in the T2-weighted TSE and FLAIR sequences, while it remains difficult to see on the T1-weighted MRRAGE sequence despite the aforementioned adjustments.
Figure 2
Figure 3
Right mesial temporal sclerosis (arrows) as seen in coronal T2-weighted TSE (left) and coronal FLAIR (right) images. Loss of volume and internal structure are seen in the coronal TSE, and T2-weighted signal increase is seen on the coronal FLAIR.
Figure 3
Figure 4
Coronal T2-weighted TSE from a healthy control subject with left hippocampal malrotation (arrow).
Figure 4
Figure 5
Dysembryoplastic neuroepithelial tumor (arrow) with a typical lobulated appearance on coronal T2-weighted TSE.
Figure 5
Figure 6
(A-C) Three examples of FCD type IIb with varying degrees of the transmantle sign. (D) FCD IIa with thickened cortex and hyperintensity on T2-weighted FLAIR.
Figure 6
Figure 7
SagittalT1-weighted MPRAGE images from two patients, one with left-sided perisylvian polymicrogyria (arrows, left panel) and the other with right-sided perisylvian polymicrogyria (arrows, right panel).
Figure 7
Figure 8
Patient with right hemimegalencephaly with polymicrogyria (arrows) in the right parieto-occipital region (T1-weighted MPRAGE coronal image).
Figure 8
Figure 9
Patient with bilateral periventricular nodular heterotopia (arrows). Both axial and sagittal views of the MRI (T1-weighted MPRAGE) are shown.
Figure 9
Figure 10
A patient with multiple cortico-subcortical and subcortical cavernous malformations (red arrows). Left: axial T2-weighted TSE; right: axial T2*-susceptibility weighted imaging which shows increased sensitivity to detect the small cavernoma in the right frontal region.
Figure 10
Figure 11
Illustration of a patient with herpes simplex encephalitis. (A, B) T2-weighted TSE axial/coronal; (C, D) T2-weighted FLAIR axial/coronal.
Figure 11
Figure 12
Patient with cerebral cysticercosis at one month (A) and three months (B) after treatment with albendazole and steroid.
Figure 12
Figure 13
Multimodal imaging with interictal FDG-PET (middle) and ictal SPECT (right) which guided focused re-review of MRI (left, T1-weighted MPRAGE sequence). Ictal SPECT data were processed using SISCOM (O’Brien et al ., 2004 ), shown with a z score of 2. The hypometabolism on interictal PET (arrow) and hyperperfusion on ictal SPECT both pointed to a region in the left orbitofrontal cortex. Detailed re-review of the MRI revealed a cortical malformation characterized by gray-white blurring and thickened cortex (arrow). Resection of this region led to postoperative seizure freedom and surgical pathology-confirmed FCD.
Figure 13
Figure 14
Language fMRI in an epilepsy patient showing left hemispheric dominance during a sentence completion task. The paradigm was taken from those recommended for presurgical language assessment from the American Society of Functional Neuroradiology (Black et al ., 2017 ).
Figure 14
Figure 15
Patient with refractory seizures arising from a brain tumor (possibly DNET) in the left mesial temporal region (amygdala and hippocampus) associated with blurring of the grey-white matter interface in the ipsilateral temporal pole. (A) Representative FLAIR coronal and axial brain sections displaying the lesion (red box); (B) Scalp EEG-fMRI analysis of left frontotemporal discharges (F7-T3) shows a maximum BOLD response on the left amygdala and hippocampus as well as an additional smaller BOLD cluster at the temporal pole (left superior temporal gyrus).
Figure 15
Figure 16
Schematic representation focusing on the use of MRI in the process of presurgical evaluation for patients with drug-resistant focal epilepsy, in the setting of surgical hypothesis forming and surgical planning.
Figure 16
Tables
Authors
1 Epilepsy Center, Cleveland Clinic, Cleveland, USA
2 Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Centre and Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada
3 Multimodal Imaging and Connectome Analysis lab, McConnell Brain Imaging Centre and Montreal Neurological Institute, McGill University, Montreal, Canada
4 Departments of Neurology, Neuroscience, and Neurosurgery, Yale University, New Haven, USA
5 Department of Neurology, University of Campinas - UNICAMP, Campinas, SP, Brazil
6 Phramongkutklao hospital, Bangkok, Thailand
7 The Florey Institute of Neuroscience and Mental Health and The University of Melbourne, Australia
8 Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, USA
9 Department of Neurosurgery, University Hospital Erlangen, Germany
10 Neurology Unit, University of Modena and Reggio Emilia, Modena, Italy
11 Hotchkiss Brain Institute, University of Calgary, Canada
* Correspondence: Paolo Federico
Room C1214a,
Foothills Medical Centre,
1403 29th Street NW,
Calgary, AB,
Canada T2N 2T9
Magnetic resonance imaging (MRI) plays a central role in the management and evaluation of patients with epilepsy. It is important that structural MRI scans are optimally acquired and carefully reviewed by trained experts within the context of all available clinical data. The aim of this review is to discuss the essentials of MRI that will be useful to health care providers specialized in epilepsy, as outlined by the competencies and learning objectives of the recently developed ILAE curriculum. This review contains information on basic MRI principles, sequences, field strengths and safety, when to perform and repeat an MRI, epilepsy MRI protocol (HARNESS-MRI) and the basic reading guidelines, and common epileptic pathologies. More advanced topics such as MRI-negative epilepsy, functional MRI and diffusion-weighted imaging are also briefly discussed. Although the available resources can differ markedly across different centers, it is the hope that this review can provide general guidance in the everyday practice of using MRI for patients with epilepsy.
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