Resolving Electroclinical–Imaging Discordance in Drug-Resistant Epilepsy: The Added Value of PASCOM Analysis

Epilepsy affects over 50 million individuals worldwide, with nearly one-third remaining drug-resistant despite optimal medical therapy. In such patients, accurate localization of the epileptogenic zone is essential to enable potentially curative epilepsy surgery. However, discordance between electroclinical data and neuroimaging findings often complicates presurgical evaluation. We report the case of a 30-year-old right-handed male with a 3-year history of drug-resistant focal epilepsy, presenting with frequent disabling seizures. Magnetic resonance imaging (MRI) was nonlesional. Interictal electroencephalography (EEG) suggested seizure onset from the left frontotemporal region. In contrast, fluorodeoxyglucose positron emission tomography (PET) demonstrated hypometabolism in the right anterior temporal and frontal cortex, creating a significant electroclinical–imaging discordance. To resolve this discrepancy, PET asymmetry after anatomical symmetrization coregistered to MRI (PASCOM) analysis was performed. Given that the PET acquisition occurred during an ictal state, PASCOM revealed focal hypermetabolism in the left mesial temporal region, concordant with EEG findings. The patient subsequently underwent electrocorticography-guided left amygdalohippocampectomy. Postoperatively, he has remained seizure-free at 3-month follow-up, with gradual tapering of antiseizure medications. Histopathological examination confirmed focal cortical dysplasia type IIb. This case underscores the critical role of advanced postprocessing techniques such as PASCOM in resolving electroclinical–imaging discordance. By enhancing the sensitivity of PET imaging, PASCOM can reveal otherwise occult epileptogenic foci, thereby facilitating accurate surgical planning and improving patient outcomes. Publication History Article published online: 15 July 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/) Thieme Medical and Scientific Publishers Private Limited A-13A, Graphix Tower 1, 6th floor, Sector 62, Noida 201309, Uttar Pradesh, India