Outcome after epilepsy surgery in patients with MRI features of bilateral ammon's horn sclerosis

In refractory temporal lobe epilepsy with unilateral ammon's horn sclerosis (uAHS) resective epilepsy surgery is an established treatment option whereas little evidence exists about the consequences of unilateral hippocampal resection in patients with bilateral ammon's horn sclerosis (bAHS). The aim of this study was to evaluate the post-surgical outcome of patients with bAHS after selective amygdalo-hippocampectomy (SAH) in comparison to uAHS patients. For this purpose, all bAHS and uAHS patients, identified at our center between 2003 and 2009 were analyzed retrospectively. Thirty-one bAHS patients and 291 uAHS patients were identified. Only 55% of the bAHS, but 80% of the uAHS patients were referred for formal pre-surgical diagnostics (p=0.001). Eleven bAHS and 127 uAHS patients underwent SAH. There was no difference in seizure-free outcome (Engel IA) at 12 months (bAHS 82% vs. 69%, p=0.40) and 24 months follow up (bAHS 57% vs. 60%, p=0.80). None of the bAHS patients became globally amnesic post-surgically. The favorable outcome in these highly selected bAHS patients suggests that bAHS patients may have a fair chance of becoming seizure-free after SAH. However, due to the large number of bAHS patients not undergoing formal presurgical evaluation, the results cannot be extrapolated to bAHS patients in general.