Purpose: Mediotemporal lobe (MTL) epilepsy (MTLE) is particularly frequent among human localization-related epilepsies. MTLE usually starts before adulthood and is most frequently associated with hippocampal sclerosis (HS). For lesional adult-onset MTLE, aetiologies, disease courses, and outcomes are unknown.
Methods: From the database of this centre, we collected all patients studied between 01/1999-12/2005 fulfilling the following criteria: (1) MTLE manifestation at age >20 years; (2) time between disease manifestation and assessment ≤6 years; (3) MTL lesion on brain MRI; (4) neuropsychological test battery applied. We classified the diagnoses and documented the paraclinical data, neuropsychological performances, and seizure and memory outcomes.
Results: Diagnoses in the 84 patients (mean age 42 years at MTLE onset) were: limbic encephalitis (LE), N=23 (27%); HS (unrelated to inflammation), N=18 (22%); tumours I/II°, N=12 (14%); amygdala lesions (increased volume and T2/FLAIR signal), N=11 (13%); other, N=20 (24%). Visible MTL affection was frequently bilateral in LE (57%) and HS (22%) patients. These groups also showed the poorest memory performance. Patients with amygdala lesions were the oldest ones (mean age 52 years); aetiology of their lesions is unclear. Treatment-dependent seizure outcomes were similar to published data without restriction to adult onset-cases. Under conservative therapy, memory performance remained stable in HS patients but improved in a proportion of LE patients.
Conclusions: The most frequent cause of lesional MTLE in young adults is LE. Its prognosis in terms of seizure and memory outcome is variable. The aetiology of amygdala lesions awaits clarification - encephalitis and dysplastic lesions are most probable candidates.