Abstracts

Rationale: A high degree of overlapping has been documented between the cognitive profiles of FLE and TLE patients. Cognitive and neuroimage studies have showed that TLE causes local damage to temporal lobe structures but also remote functional and structural abnormalities on frontal lobes suggesting speeded damage to cortical areas beyond the epileptic focus. To our knowledge, no studies assessing the extension functional damage has been carried out on FLE population. Objectives: To study the effect of frontal lobe epilepsy on the functional networks involved on memory encoding. In particular we will study the local effect of seizure focus on frontal lobe and the remote effect of epilepsy on temporal lobe networks activated during memory encoding. To study the profile of memory impairment on FLE. Methods: We studied 39 FLE patients (19 with left 15 with right epileptic foci and 5 non lateralized) and 20 healthy volunteers using a memory encoding fMRI paradigm on a 3T scanner followed by a recognition test out of the scanner. Activation maps for the blocks of different stimuli and for the events successfully remembered where created with SPM5 software and compared between groups. Analysis of performance and neuropsychological evaluation was carried out. Results: Patients with FLE are impaired on memory tasks of long term recognition and verbal and non verbal learning. Memory impairment on FLE is not material specific. Maps of activation showed no differences on the activation of medial temporal structures between controls and FLE patients. FLE patients recruited wider areas of activation including mid frontal gyrus, perisylvian cortices and SMA during the presentation of to memorize items. These activations are mainly located on the contra lateral frontal lobe to the epileptic focus. Conclusions: Activation of mid temporal structures during a memory tasks in FLE patients is comparable to controls. Our results does not show evidence of dysfunction of mesial temporal structures on FLE. FLE patients recruit wider areas during the task suggesting a possible compensatory mechanism of the frontal lobe dysfunction.