Clinical features and outcomes of late-onset epilepsy of unknown etiology: A retrospective study in West China.

Abstract

Purpose: Late-onset epilepsy (LOE) usually refers to the development of epilepsy at the age of 50 years or older. Approximately 20 % of LOE cases are diagnosed as late-onset epilepsy of unknown etiology (LOUE) due to a lack of an identifiable cause. The aim of this study was to investigate the clinical features, seizure and cognitive outcomes of patients with LOUE in West China.

Methods: Patients diagnosed with LOUE at West China Hospital between January 2015 and December 2022 were retrospectively recruited. The seizure and cognitive outcome were followed up for at least 1 year after discharge. Logistic regression models were applied to investigate the risk factors of recurrent seizure and cognitive impairment in patients with LOUE.

Results: We included 286 LOUE patients with a median seizure onset age of 59 years. The most common seizure types were focal to bilateral tonic-clonic seizure (61.9 %) and focal non-motor seizure (37.0 %). Two-hundred and seventy-seven (96.9 %) patients underwent video electroencephalography (VEEG), with seizures recorded in 11.9 % of patients and interictal epileptiform discharges in 58.2 % cases. Majority of the patients (73.4 %) received monotherapy, with levetiracetam, oxcarbazepine and valproate being the most commonly prescribed anti-seizure medications. During the follow-up, 69.1 % of patients achieved seizure-free. Multivariate analysis identified ictal event recorded during VEEG monitoring (OR:0.205, 95 % CI: 0.045-0.932, p = 0.040) and memory impairment (OR:2. 470, 95 % CI: 1.181-5.167, p = 0.016) as significant factors associated with recurrent seizure. Twenty-two patients were classified as cognitive impairment. The onset age (OR:1.095, 95 % CI:1.032-1.162, p = 0.003) and total Fazekas score (OR = 6.770, 95 % CI:1.972-23.241, p = 0.002) were significant risk factors associated with cognitive dysfunction.

Conclusion: LOUE is generally a benign form of epilepsy with a high percentage of patients achieving seizure-free status. However, these patients are at a higher risk of memory decline and cognitive dysfunction.