Nuclear imaging for localization and surgical outcome prediction in epilepsy: A review of latest discoveries and future perspectives

Abstract

Background: Epilepsy is one of the most common neurological disorders. Approximately, one-third of patients with epilepsy have seizures refractory to antiepileptic drugs and further require surgical removal of the epileptogenic region. In the last decade, there have been many recent developments in radiopharmaceuticals, novel image analysis techniques, and new software for an epileptogenic zone (EZ) localization.

Objectives: Recently, we provided the latest discoveries, current challenges, and future perspectives in the field of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) in epilepsy.

Methods: We searched for relevant articles published in MEDLINE and CENTRAL from July 2012 to July 2022. A systematic literature review based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis was conducted using the keywords "Epilepsy" and "PET or SPECT." We included both prospective and retrospective studies. Studies with preclinical subjects or not focusing on EZ localization or surgical outcome prediction using recently developed PET radiopharmaceuticals, novel image analysis techniques, and new software were excluded from the review. The remaining 162 articles were reviewed.

Results: We first present recent findings and developments in PET radiopharmaceuticals. Second, we present novel image analysis techniques and new software in the last decade for EZ localization. Finally, we summarize the overall findings and discuss future perspectives in the field of PET and SPECT in epilepsy.

Conclusion: Combining new radiopharmaceutical development, new indications, new techniques, and software improves EZ localization and provides a better understanding of epilepsy. These have proven not to only predict prognosis but also to improve the outcome of epilepsy surgery.

Keywords: PET; SPECT; epilepsy; nuclear medicine; presurgical localization; radiopharmaceuticals; techniques.

Figure 1

PRISMA flow diagram for the study recruitment. A final 162 studies were included.

Figure 2

Non-FDG radiotracers used in epilepsy in the last decade. Radiotracers with a downward arrow, upward arrow, or upward double arrow showed decreased uptake, increased uptake, or increased volume of distribution, respectively.

Figure 3

Neuroimaging modalities using various methods and software for epileptogenic zone localization and surgical outcome prediction. AI, asymmetry index; BMA, Bayesian modeling average; DTI, diffusion tensor imaging; DWI, diffusion-weighted imaging; ECoG, electrocorticography; EEG, electroencephalogram; ESI, EEG source image; ETE, extratemporal lobe epilepsy; fMRI, functional MRI; HA, hypometabolism asymmetry; MEG, magnetoencephalography; MRI, magnetic resonance imaging; PET, positron emission tomography; PML, percentage metabolism loss; SEEG, stereotactic EEG; SISCOS, subtraction ictal SPECT coregistered to interictal SPECT; SISCOM, subtraction ictal SPECT coregistered to MRI; SPECT, single-photon emission computed tomography; SPM, statistical parametric mapping; STATISCOM, statistical ictal SPECT coregistered to MRI; SUV, standard uptake value; SUVr, SUV ratio; 3D-SSP, three-dimensional stereotactic surface projection.