title: MRI-negative temporal lobe epilepsy-What do we know?
abstract: Temporal lobe epilepsy (TLE) is the most common focal epilepsy in adults. TLE has a high chance of becoming medically refractory, and as such, is frequently considered for further evaluation and surgical intervention. Up to 30% of TLE cases, however, can have normal ("nonlesional" or negative) magnetic resonance imaging (MRI) results, which complicates the presurgical workup and has been associated with worse surgical outcomes. Helped by contributions from advanced imaging techniques and electrical source localization, the number of surgeries performed on MRI-negative TLE has increased over the last decade. Thereby new epidemiologic, clinical, electrophysiologic, neuropathologic, and surgical data of MRI-negative TLE has emerged, showing characteristics that are distinct from those of lesional TLE. This review article summarizes what we know today about MRI-negative TLE, and discusses the comprehensive assessment of patients with MRI-negative TLE in a structured and systematic approach. It also includes a concise description of the most recent developments in structural and functional imaging, and highlights postprocessing imaging techniques that have been shown to add localization value in MRI-negative epilepsies. We evaluate surgical outcomes of MRI-negative TLE, identify prognostic makers of postoperative seizure freedom, and discuss strategies for optimizing the selection of surgical candidates in this group.
authors.affiliation: University of California San Francisco (UCSF), San Francisco, California, U.S.A.|University of Alabama Birmingham (UAB), Birmingham, Alabama, U.S.A.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Muhlhofer
authors.affiliation: University of California San Francisco (UCSF), San Francisco, California, U.S.A.|National Neuroscience Institute, Singapore, Singapore.
authors.forename: Yee-Leng
authors.initials: YL
authors.lastname: Tan
authors.affiliation: University of California San Francisco (UCSF), San Francisco, California, U.S.A.|Center for Imaging of Neurodegenerative Diseases (CIND), San Francisco, California, U.S.A.|Department of Radiology, UCSF, San Francisco, California, U.S.A.
authors.forename: Susanne G
authors.initials: SG
authors.lastname: Mueller
authors.affiliation: University of California San Francisco (UCSF), San Francisco, California, U.S.A.
authors.forename: Robert
authors.initials: R
authors.lastname: Knowlton
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000927:Anticonvulsants / Q000009:adverse effects / Q000627:therapeutic use; D001284:Atrophy; D004351:Drug Resistance; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D005911:Gliosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D011183:Postoperative Complications / Q000175:diagnosis; D011379:Prognosis; D013702:Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000927:Anticonvulsants
keywords: Epileptogenic network in TLE; FDG-PET-positive TLE; Histopathology TLE; Semiology in temporal lobe epilepsy; Surgical outcomes in TLE; TLE with normal MRI