Age at onset of epilepsy shapes neurocognitive profiles in focal cortical dysplasia

Abstract

Background: Focal cortical dysplasia (FCD) is a common developmental brain disorder frequently associated with refractory epilepsy and neurocognitive comorbidities. This study examines the neurocognitive profiles of patients with FCD, with particular attention to histopathological classification, age at onset of epilepsy (AOE), FCD lateralization and localization, and antiseizure medication (ASM) load. Methods: This study was conducted on 98 patients with FCD (type IIa: n = 26, type IIb: n = 59) who had undergone surgical treatment for epilepsy. Patients underwent comprehensive presurgical neuropsychological assessments for intelligence (IQ) and six cognitive domains. Results: Patients with FCD type IIb significantly more often exhibited an earlier AOE (< 6 years, 65.5% vs. 38.5%, p = 0.021) and a longer duration of epilepsy at the time of cognitive testing (mean ± SD, 18.8 ± 13.61 vs. 11.88 ± 9.09 years, p = 0.008) compared to patients with FCD type IIa. The most notable differences in cognitive performance were observed between patients with early (< 6 years) and late AOE (≥ 6 years) for IQ and motor functions. In these domains, patients with early AOE consistently scored lower (IQ: 2.24 ± 1.17 vs. 2.79 ± 0.83, p = 0.021, impaired patients: 36% vs.15.8%; motor function: 1.46 ± 1.05 vs. 2.25 ± 0.95, p = 0.002, impaired patients: 74.4% vs. 43.8%). Differences in cognitive performance were not linked to FCD type, lateralization, localization, or ASM load. Conclusion: Our findings indicate that the AOE emerged as the determining factor for cognitive performance in refractory epilepsy patients due to FCD. As expected in cases of early childhood onset epilepsies, a neurodevelopmental disruption particularly of IQ and motor function was seen.