Reappraisal and Practical Application of International League Against Epilepsy ( ILAE 1989 ) Classification of Localization-Related Epilepsies in Adult

ABSTRACT

BACKGROUND: Since 1985 when ILAE proposed its first classification system of epilepsy, many studies have reported the practical applicability of the system. However, its limitations have been elucidated. In order to find out the applicability and limitations of the ILAE classification system and the role that diagnostic parameters (semiology, EEG and MRI) take in the anatomical localization of localization-related epilepsies (LREs), we investigated the clinical data of adult patients with LRE in step-wise way. METHOD: We recruited 173 patients with newly-referred/diagnosed LRE from our departmental data registry. Idiopathic epilepsies were excluded. We evaluated the anatomical localization rate(LR) according to each diagnostic parameter, the concordant localization rate(CLR) between two parameters and between three parameters. LR in total patients by any one of three diagnostic parameters was also evaluated. MRI abnormalities were evaluated in those patients showing concordant localization between semiology and EEG. RESULTS: The highest anatomical LR(67.1%) was reported in the semiological parameter. CLR between semiology and EEG was 28.9%. CLR between three parameters was 16.2%. MRI abnormalities were seen in 60% of patients with concordant localization between semiology and EEG. Fifty six percent of electroclinically concordant patients showed concordant localization with an MRI and 79% of them were concordantly localized in the temporal lobe. The LR in total patients was 71.7%. In each of the evaluation steps, the temporal lobe LR was the highest. CONCLUSIONS: Total lobar LR by any one diagnostic parameter in all the patients was high according to the ILAE diagnostic criteria. Semiology was the best localizing parameter, however, combined evaluation with either EEG or MRI reduced the localizability. Even though the MRI study showed a significant discordance rate in patients with electroclinical localizations, it could identify the underlying etiology in a major proportion of the patients. This study showed the importance of an imaging study in the lobar localization of LREs combined with an electroclinical localization by the ILAE classification system.