Abstracts

Rationale: Medial Temporal Lobe Epilepsy (MTLE) is a common focal epilepsy which frequently becomes medically refractory. Temporal Lobe Surgery (TLS) in the form of Anterior Temporal Lobectomy (ATL) or Selective Amygdalohippocampectomy (SAH) coveys freedom from disabling seizures in 50 - 66%. Progressive temporal and extra-temporal white matter changes following TLS have been previously described using longitudinal MRI, however, little is known about post-operative gray matter change--particularly, in the contralateral hippocampus. This is an imporant question considering that pre-operative evaluation endeavors to maximize the chance of seizure freedom while minimizing neurocognitive sequelae by identifying the epileptogenic zone and sparing the contralateral (aka 'good') hippocampus. Methods: Serial, 1.5T, T1-weighted MRI scans were acquired in 9 MTLE patients all with Mesial Temporal Sclerosis (MTS) (pathologically proven or presumptively based on characteristic T2-relaxometry values) treated with ATL (n=7) or SAH (n=2) and three controls. Patients were imaged preoperatively and serially on post-operative day (POD) 1, 2, 6, 30, 60 and 120. A very delayed (>3 year) scan was acquired in 6 patients. Healthy controls were scanned at identical intervals. Hippocampal body volume (HBV) was measured at all time points by a trained-observer blinded to the post-operative time point using a manual segmentation protocol. Results: In the TLS group, repeated measures ANOVA revealed a statistically significant decrease (p < 0.05, Bonferroni, post-hoc) in mean HBV from baseline (1255 mm3 +/- 131) to POD 6 (894.3 mm3 +/- 106) and POD 60 (921.1 mm3 +/- 171) but no statistically significant interval atrophy between POD 6 and POD 60 (table 1). In addition there was statistically significant atrophy between POD 60 (921.1 mm3 +/- 171) and delayed (>