Abstracts

Rationale: Episodic memory impairments caused by temporal lobe epilepsy (TLE) are well documented in the literature. Standard clinical episodic memory tests typically include a 30-min delayed recall test. However, in the past decade, it has become apparent that this standard test does not capture the full range of memory problems in TLE patients. Some patients perform well on a standard 30-min delayed recall test, but show Accelerated Long-term Forgetting (ALF) after 24 h. Although ALF has been investigated in patients with different types of epilepsy, current research on resected TLE patients is missing. In the present study, resected TLE patients were compared to a control group matched on initial learning. Methods: Sixty participants were included in the current study, 30 resected TLE patients and 30 control participants. All patients underwent standard antero-temporal lobectomy with amygdalohippocampectomy (ATL þ AH), 13 in the left hemisphere and 17 in the right one. Patients were compared to an education- and age-matched control group of 30 participants. Participants performed the Rey Auditory Verbal Learning Test (RAVLT), which is an established neuropsychological test to measure the ability to encode, store, and recover verbal information. Rehearsal effects were prevented by performing the Matrix Reasoning Subtest of the Wechsler Adult Intelligence Scale (WAIS III) in the 30 min delay of the RAVLT. The encoding phase of the RAVLT included five repetitions of the word list, followed by 30-min and one-week delayed recall phases. We looked for impaired episodic memory after 30 min and after one week, as well as a group by delay interaction to investigate ALF. Results: Thirteen patients underwent the temporal lobectomy in the left hemisphere and 17 in the right one. Mean age at epilepsy onset was 8.9 years (range1-40), and surgery had been performed 27.8 years (range 1-59) after onset. At the time of our study, the mean age of the patients was 41.3 years (range 19-62). Twenty-six patients were in the late post-operative phase (after 12 months), and four patients were in the early post-operative phase (between 6 and 12 months). Seizure frequency decreased in all patients after surgery; 16 patients were seizure-free. The performance on immediate learning was matched for the three groups. Resected TLE patients showed normal performance on verbal recall after 30 min, but impairments became apparent after one week. Moreover, the significant interaction between participant group and memory test delay demonstrated that the patients indeed showed an acceleration in forgetting. Furthermore, ALF was present in both left and right resected TLE patients. In addition, ALF was observed also in seizure-free resected TLE patients. Conclusions: ALF was found in patients with TLE who underwent standard temporal lobectomy, both those with right and those with left hemisphere resection. This   condition seems independent of seizure outcome. Funding: No funding was received in support of this abstract