The utility of arterial spin labeling in the presurgical evaluation of poorly defined focal epilepsy in children

Abstract

OBJECTIVEThe authors sought to assess the utility of arterial spin labeling (ASL) perfusion 3T-MRI for the presurgical evaluation of poorly defined focal epilepsy in pediatric patients.METHODSPseudocontinuous ASL perfusion 3T-MRI was performed in 25 consecutive children with poorly defined focal epilepsy. ASL perfusion abnormalities were detected qualitatively by visual inspection and quantitatively by calculating asymmetry index (AI) maps and significant z-score cluster maps based on successfully operated cases. ASL results were prospectively compared to scalp EEG, structural 3T-MRI, FDG-PET, ictal/interictal SPECT, magnetoencephalography (MEG), and intracranial recording results, as well as the final surgically proven epileptogenic zone (EZ) in operated patients who had at least 1 year of good (Engel class I/II) seizure outcome and positive histopathology results.RESULTSQualitative ASL perfusion abnormalities were found in 17/25 cases (68%), specifically in 17/20 MRI-positive cases (85.0%) and in none of the 5 MRI-negative cases. ASL was concordant with localizing scalp EEG findings in 66.7%, structural 3T-MRI in 90%, FDG-PET in 75%, ictal/interictal SPECT in 62.5%, and MEG in 75% of cases, and with intracranial recording results in 40% of cases. Eleven patients underwent surgery; in all 11 cases the EZ was surgically proven by positive histopathology results and the patient having at least 1 year of good seizure outcome. ASL results were concordant with this final surgically proven EZ in 10/11 cases (sensitivity 91%, specificity 50%). All 10 ASL-positive patients who underwent surgery had positive surgical pathology results and good long-term postsurgical seizure outcome at a mean follow-up of 39 months. Retrospective quantitative analysis based on significant z-score clusters found 1 true-positive result that was missed by qualitative analysis and 3 additional false-positive results (sensitivity 100%, specificity 23%).CONCLUSIONSASL supports the hypothesis regarding the EZ in poorly defined focal epilepsy cases in children. Due to its convenience and noninvasive nature, the authors recommend that ASL be added routinely to the presurgical MRI evaluation of epilepsy. Future optimized quantitative methods may improve the diagnostic yield of this technique.

ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions

“…Early imaging should be repeated after 2 years of age when myelination is likely to be complete, if there is a suspicion of a focal structural lesion, or in infants with refractory infantile spasms of unknown etiology. Optimized imaging and analysis for the detection of subtle focal cortical dysplasia may be necessary, and modalities such as fluorodeoxyglucose positron emission tomography or arterial spin labeling can be useful to detect focal structural anomalies in the presence of an apparently normal MRI 143,144 . Such children should be referred early for epilepsy surgical assessment.…”

“…Optimized imaging and analysis for the detection of subtle focal cortical dysplasia may be necessary, and modalities such as fluorodeoxyglucose positron emission tomography or arterial spin labeling can be useful to detect focal structural anomalies in the presence of an apparently normal MRI. 143,144 Such children should be referred early for epilepsy surgical assessment. In addition, MRI abnormalities may point to specific metabolic disorders.…”

Making the Invisible Visible: Advanced Neuroimaging Techniques in Focal Epilepsy

“…In addition to nuclear imaging, recent advances in functional neuroimaging may further improve the detection of focus. Arterial spin labeling (ASL) is a non-invasive method to visualize brain perfusion by MRI ( Haller et al, 2016 ) and, thus, expected to detect abnormal cerebral blood flow, particularly interictal reduction, around the epileptogenic foci in epilepsy ( Figure 7 ) ( Boscolo Galazzo et al, 2016 ; Shang et al, 2018 ; Wang et al, 2018 ; Sone et al, 2019 ; Lam et al, 2020 ). Although ASL might not surpass 18 F-FDG PET in terms of detectability of focus ( Sone et al, 2019 ), its non-invasive nature and wide availability will guarantee a supplemental role in clinical practice.…”

Presurgical focus localization in epilepsy

“…Eleven studies evaluated standard MRI sequences [72][73][74][81][82][83][84][85][86][87][88] , five evaluated additional MRI sequences 69,[89][90][91][92] , and three contained data on both standard and additional sequences 93,94 . Six studies were on DTI [96][97][98][99][100][101] .…”

“…Sample sizes varied between 6 and 98 patients. Thirteen studies included both children and adults, two only children 81,92 and two mostly adults 69,90 . Two publications did not report the age of the study population 85,88 .…”