Delayed Diagnosis of Lesional Epilepsy: Utility of Modern Imaging

Steven M. Tanabe, P. Ellen Grant, G. Rees Cosgrove, Daniel B. Hoch, and Andrew J. Cole

Published: 07 April 2000

Although MRI examination is generally recommended in patients with focal epilepsy, we have encountered a population of individuals with chronic epilepsy who have never undergone a high-resolution imaging examination. We sought to identify factors in the history and prior evaluation that led to an incorrect diagnosis of cryptogenic epilepsy with overlooked lesions. We identified and retrospectively reviewed 10 patients referred to a tertiary-care hospital-based epilepsy clinic from 1993­1999 with longstanding localization-related epilepsy in whom initial brain MRI, obtained years after seizure onset, demonstrated focal lesions. Structural lesions were identified on MRI in each case that were concordant with the clinical, interictal, and when available, ictal electrographic localization of their seizure foci. Lesions included gray matter heterotopia, low-grade glioma, nonspecific gliosis, congenital encephalomalacia, remote intraparenchymal hemorrhage, cavernous malformation, and mesial temporal sclerosis. Lesions identified in each case were potentially amenable to surgical treatment. In every case, the recognized lesion was probably present decades before discovery. The median duration of epilepsy prior to MRI examination in this population was 26 years, indicating that the epilepsy diagnosis was assigned before MRI became widely available. We conclude that there is a population of "MRI-naïve" epilepsy patients whose diagnosis predates the widespread availability of MRI and who harbor chronic lesions that are causally related to their seizures and are amenable to surgical resection. MRI may be underutilized in patients with longstanding epilepsy. Identification of unsuspected lesions may decrease epileptic morbidity and mortality.

Keywords: Epilepsy, Intractable, MRI, Diagnosis, Lesion