Introduction It is unknown why over one-third of patients with mesial temporal lobe epilepsy (mTLE) and hippocampal sclerosis (HS) continue to experience seizures despite temporal lobe surgery. We investigated the relationship between hippocampal internal architecture (HIA) on preoperative MRI, and postoperative seizure outcome in patients with refractory mTLE and HS.

Methods HIA was assessed on preoperative T2-STIR MR images using a published scoring system1 for 79 patients undergoing evaluation at University Hospital Bonn, Germany. Patients underwent amygdalohippocampectomy and received postoperative outcome assessment using the International League Against Epilepsy (ILAE) classification. Hippocampal volumes were obtained using 3D T1-weighted images. Quantitative histopathological assessment was performed on resected hippocampal specimens.

Results No significant differences in ipsilateral or contralateral HIA ratings, or HIA score asymmetry, were found between patients rendered seizure free (ILAE I) compared to those continuing to experience postoperative seizures (ILAE II-VI). HIA significantly correlated with neuronal density in CA3 and CA4 in the pathologic hippocampus, and hippocampal volumes bilaterally. There was no significant correlation between HIA and clinical variables.

Conclusion Although valuable in determining seizure laterality, HIA does not predict postoperative outcome.

Acknowledgements This work was supported by a UK MRC grant awarded to SSK (Grant Number: MR/K023152/1). References:1Ver Hoef 2013