Brain imaging in the assessment for epilepsy surgery

Abstract

Brain imaging has a crucial role in the presurgical assessment of patients with epilepsy. Structural imaging reveals most cerebral lesions underlying focal epilepsy. Advances in MRI acquisitions including diffusion-weighted imaging, post-acquisition image processing techniques, and quantification of imaging data are increasing the accuracy of lesion detection. Functional MRI can be used to identify areas of the cortex that are essential for language, motor function, and memory, and tractography can reveal white matter tracts that are vital for these functions, thus reducing the risk of epilepsy surgery causing new morbidities. PET, SPECT, simultaneous EEG and functional MRI, and electrical and magnetic source imaging can be used to infer the localisation of epileptic foci and assist in the design of intracranial EEG recording strategies. Progress in semi-automated methods to register imaging data into a common space is enabling the creation of multimodal three-dimensional patient-specific datasets. These techniques show promise for the demonstration of the complex relations between normal and abnormal structural and functional data and could be used to direct precise intracranial navigation and surgery for individual patients.

Learning to see the invisible: A data‐driven approach to finding the underlying patterns of abnormality in visually normal brain magnetic resonance images in patients with temporal lobe epilepsy

“…2 Hippocampal sclerosis is generally visually recognized from a reduced hippocampal volume and a higher T2/FLAIR signal arising from within the hippocampus. The hippocampus is conventionally focused on by radiologists reporting MRI scans in patients with TLE, as hippocampal sclerosis is a common cause of TLE.…”

“…1,2 Focal epilepsy accounts for a significant proportion (around two-thirds) of those cases that do not respond to medication, and the temporal lobe is the most common site of onset of focal seizures. However, one-third of patients continue to have frequent seizures despite optimal medical therapy.…”

“…However, one-third of patients continue to have frequent seizures despite optimal medical therapy. 2 This leaves one-third of pharmacoresistant patients with no visually identifiable target for neurosurgery (the MRI-negative cases). If focal epilepsy does not respond to medication, neurosurgical procedures can be considered.…”

Recommendations for the use of structural magnetic resonance imaging in the care of patients with epilepsy: A consensus report from the International League Against Epilepsy Neuroimaging Task Force

“…Third, they consider review papers, evidence-based guidelines, and reports on the role of structural MRI in the diagnosis and management of seizure disorders, [14][15][16][17][18][19][20][21][22][23][24][25] with particular attention to studies that meet at least some standards for evidence classification. First, they build upon previous ILAE neuroimaging reports.…”

The promise of subtraction ictal SPECT co-registered to MRI for improved seizure localization in pediatric epilepsies: Affecting factors and relationship to the surgical outcome

“…However, its spatial specificity is poor (≥ 2 cm) and cannot be used by itself for surgical planning. Imaging modalities hold promise for this purpose 6 but have various limitations, particularly in pediatric patients. Magnetic Resonance Imaging (MRI) can only image structural abnormalities potentially associated with seizures or structural changes, such as loss of hippocampal volume that occur as the result of seizures 7,8,9 .…”