PURPOSE: The aim of this project was to study the microstructural architecture of the contralateral hippocampus to the affected side in patients with temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) and its relation with surgical outcome.
METHOD: The team included 33 consecutive patients evaluated in our epilepsy surgery program during a five-year period. They underwent a presurgical MRI with volumetric T1 and diffusion weighted sequences. 22 patients with TLE-HS (13 women, 12 right TLE-HS) were finally selected. Median follow-up after surgery was 6.25 years (4.5-8.83 years). The team segmented the hippocampal subfields of the contralateral hippocampus using FreeSurfer and calculated the fractional anisotropy (FA) and the mean diffusivity (MD) of each subfield. Researchers also scanned 18 healthy age-matched controls.
RESULTS: After surgery, 50% of the patients (n = 11) remained seizure-free (SF) following surgery. Comparing non-SF to SF patients, the MD showed increased values of the CA1 (p = 0.035), the molecular layer (p = 0.010) and the dentate gyrus (p = 0.041) in the healthy hippocampus. Using a cut-off point for a survival analysis, we found that patients with lower values of MD of the molecular layer and the CA1 remained SF during long-term post-operative follow-up (p < 0.0001).
CONCLUSIONS: The contralateral hippocampal internal microstructure may have be implicated in post-surgery seizure freedom in patients with temporal lobe epilepsy with hippocampal sclerosis.