FDG-PET and Magnetoencephalography in Presurgical Workup of Children with Localization-related Nonlesional Epilepsy

Purpose: 2-[18F]Fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) and magnetoencephalography (MEG) may assist in identifying the epileptogenic zone in children with nonlesional localization-related epilepsy. The aim of this study was to evaluate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of FDG-PET, MEG, FDG-PET + MEG, and FDG-PET/MEG in children with nonlesional localization-related epilepsy.

Methods: Twenty-six children with localization-related epilepsy and who had normal or subtle changes on magnetic resonance imaging (MRI) underwent FDG-PET and MEG. Twenty-two patients had surgical resection, and surgical outcome was assessed using Engel classification. In patients with Engel I seizure outcome, we assessed the sensitivity, specificity, PPV, and NPV of lobar localization of MEG, FDG-PET, FDG-PET + MEG, and FDG-PET/MEG.

Key Findings: Sixteen (72.7%) of 22 had Engel I seizure outcome. MEG was concordant with surgical resection in 18 patients, 14 had Engel I, and four had Engel II-IV outcomes. MEG was nonlocalizing or nonconcordant in four patients; two patients had Engel I and two had Engel II-IV outcomes. FDG-PET was concordant with surgical resection in 14 patients; 9 had Engel I outcome, and 5 had Engel II-IV outcome. FDG-PET was nonlocalizing or nonconcordant in seven patients with Engel I, and one with Engel III outcome. The sensitivity, specificity, PPV, and NPV of MEG were 85.0%, 99.1%, 94.4%, and 97.3%, respectively. The sensitivity, specificity, PPV, and NPV of FDG-PET were 65.0%, 94.4%, 68.4%, and 93.6%, respectively. There was no significant difference between MEG and FDG-PET for concordance with surgical resection (χ(2)  = 2.794, p = 0.095). FDG-PET + MEG, defined as two tests concordant with surgical resection, had reduced sensitivity and NPV, but increased specificity and PPV (55.0%, 92.3%, 100%, and 100%, respectively) relative to individual tests. FDG-PET/MEG, defined as one or both test(s) concordant with surgical resection, had increased sensitivity and NPV but reduced specificity (95.0%, 99.0%, and 93.5%, respectively) relative to individual tests.

Significance: The two tests FDG-PET and MEG were complementary in the assessment of children with localization-related epilepsy, particularly when one test was nonlocalizing or nonconcordant.