Abstracts

Rationale: In refractory temporal lobe epilepsy (TLE) with unilateral ammon`s horn sclerosis (uAHS), selective amygdalo-hippocampectomy (SAH) is an established surgical treatment option. The aim of this study was to evaluate how many TLE patients with bilateral AHS (bAHS) are presurgically studied, how many qualify for SAH, and which proportion of them becomes seizure free after operation. Methods: All patients with TLE diagnosed with bAHS by MRI-T2-relaxometry at this center from 2003-2009 were retrospectively identified. As control cohort, 6 patients of each year of the inclusion period with the MRI diagnosis of uAHS were assessed. All data were obtained from the records of this center. Results: Thirty-one patients with bAHS were identified (median age at disease onset: 20 years [yrs]; 0.4-64 yrs). Seventeen of them underwent non-invasive surgical diagnostics. In 15 of these 17 patients invasive presurgical diagnostics with intrahippocampal depth electrodes were performed. Eleven of these 15 patients underwent SAH (35 % of all bAHS patients; median disease duration at operation: 25 yrs; 3-58 yrs). These patients had a median of 4 clinical seizures (1-10) with implanted electrodes; 67-100% of them emerged from the resected hippocampus (in the following, “lateralization ratio”). Of the 11 operated patients, 9 were seizure-free (81%) after a median follow up of 1 yr (0.3-5 yrs). The seizure free patients had a median lateralization ratio of 100% (71-100%); the respective ratios in the non-seizure-free patients were 67% and 100%. Forty-two patients with MRI features of uAHS were identified (median age at disease onset: 11 yrs, 0.5-68 yrs, difference to bAHS group not significant [n.s.], Mann-Whitney-U-test). Thirty-nine of them underwent non-invasive presurgical diagnostics. Due to inconclusive results, 17 of these 39 patients underwent invasive presurgical diagnostics with intrahippocampal depth electrodes. Fifteen of the implanted patients and 18 with non-invasive studies only were finally operated. To sum, 33 uAHS patients underwent SAH (79 % of all uAHS patients. median disease duration at operation 23 yrs, 5-56 yrs, n.s., Mann-Whitney-U-test), a significantly larger proportion than in the bAHS group (Fisher’s exact test). 25 of 33 operated uAHS patients were seizure free (75%) after a median follow up of 2 yrs (0.2-6 yrs; n.s., Mann-Whitney-U-test). Histopathology was concordant with the diagnosis of AHS in all patients. Conclusions: Patients suffering from refractory TLE with bAHS should not be excluded from presurgical diagnostics per se. In our cohort, the proportion of patients finally operated on was lower in the bAHS compared to the uAHS patients. However, the seizure-free outcome in both groups was not different. Also, no differences were found in age at disease onset or disease duration at operation. To achieve sufficient diagnostic certainty, intracranial EEG recordings are probably inevitable in bAHS patients. Further studies are required to compare the memory outcome in bAHS and uAHS patients before and after SAH.