Abstracts

Rationale: Patients with refractory seizures in the context of medial temporal lobe epilepsy (MTLE) associated with major bilateral hippocampal atrophy (HA) are often considered poor candidates for unilateral resective surgery. This view is based on the understanding that seizures are likely to recur after operation and also that resection may lead to unacceptable cognitive sequelae, particularly regarding episodic memory. Objective: To report surgical outcome in regard to post-op seizures and performance on neuropsychologic tests in patients with MTLE and major bilateral HA. Methods: Eight patients with refractory MTLE and major bilateral HA were evaluated and operated at our Center between 2003 and 2007. Wada test was performed in 2 patients with predominant left HA. Vídeo-EEG showed unitemporal seizure origin in all, and therefore all 8 underwent selctive amygdalo-hippocampectomy (5L, 3R). Detailed post-op neuropsychological testing at least 6 months after operation and post-op follow-up of at least 2 years are available for 6 patients, at the time of writing. Results: Five of the 6 patients (83%) followed for at least 2 years are seizure free, although in 3 there were transitory recurrences upon reduction or cessation of antiepileptic medication. The other 2 patients were operated during 2007 and have also been seizure free. None of the 8 patients had global amnesia. Even though post-op neuropsychological performance was heterogeneous, 3 of the 6 patients re-tested so far had increased visual or verbal episodic memory scores. Conclusions: Unilateral resection of mesial temporal structures in patients with MTLE associated with major bilateral HA is both effective and safe, suggesting that the mesial TL structures of only one hemisphere are usually responsible for seizure generation and also that neuroplasticity is likely to play a role as epilepsy progresses, re-shaping distributed networks linked to episodic memory.