Surgical outcome of patients with bilateral ammon's horn sclerosis after unilateral amygdalo-hippocampectomy

Introduction: In refractory temporal lobe epilepsy with unilateral ammon's horn sclerosis selective amygdalo-hippocampectomy is an established treatment in epilepsy surgery. The aim of this study is to evaluate how many patients with temporal lobe epilepsy and bilateral ammon's horn sclerosis benefit from unilateral selective amygdalo-hippocampectomy and if these have particular features.

Methods: All patients with temporal lobe epilepsies diagnosed with MRI features of bilateral ammon's horn sclerosis at this center from April 2003 to March 2009 were retrospectively collected for this study in a local database search. Of special interest was to evaluate those patients with refractory epilepsies who underwent non-invasive or invasive presurgical diagnostics and their outcome after unilateral amygdalo-hippocampectomy.

Results: Thirty-one patients with bilateral ammon's horn sclerosis were identified (median age at disease onset: 16 years; 0.4–64 years). Twenty-one of them underwent non-invasive surgical diagnostics. In 16 patients invasive presurgical diagnostics with intrahippocampal depth electrodes were performed. Eleven of them underwent selective amygdalo-hippocampectomy. These patients had a 67–100% proportion of seizures emerging from the resected hippocampus. In all cases, histopathology was concordant with the diagnosis of ammon's horn sclerosis. Of the eleven operated patients, eight were seizure free after a median follow up of 1 year (range 0.5–5 years).From the post-surgical seizure free patients 6 had a history of febrile seizures (75%), whereas febrile seizures were reported by only 8/31 patients (26%) of the general study group (P=0.005, Fisher's exact test).

Discussion: Patients suffering from refractory temporal lobe epilepsies with bilateral ammon's horn sclerosis should not be excluded from persurgical diagnostics per se. Fifty-two percent of patients with bilateral ammon's horn sclerosis undergoing presurgical studies were finally operated on, and 73% of these patients became seizure free. To achieve sufficient diagnostic certainty, intracranial EEG recordings are inevitable. A history of febrile seizures seems to be associated with a seizure free post-surgical outcome.