• Temporal lobe epilepsy;
  • Epilepsy surgery;
  • MRI;
  • Volumetry;
  • Proton magnetic resonance spectroscopy;
  • Neuropsychology;
  • Memory

Summary:  Purpose: To examine the relationship between hippocampal volumes, 1H magnetic resonance spectroscopy (MRS)-identified hippocampal metabolic function, and verbal memory in patients with unilateral mesial temporal lobe epilepsy (MTLE).

Methods: Hippocampal volumes, 1H MRS-derived hippocampal creatine to N-acetylaspartate (Cr/NAA), and verbal memory assessment were obtained preoperatively in 22 patients (six right, 16 left) with EEG-defined unilateral MTLE.

Results: Left hippocampal volume correlated significantly with left hippocampal Cr/NAA (r = −0.549, p < 0.01), whereas right volume correlated significantly with right Cr/NAA (r = −0.478, p < 0.05). Verbal memory correlated significantly with left hippocampal Cr/NAA (r = −0.594, p < 0.01), but not with left hippocampal volume or right hippocampal measures.

Conclusions: Hippocampal volumes and 1H MRS-derived metabolite ratios are statistically related, but share only a small percentage of variance, suggesting separate but related pathophysiologic processes. Left hippocampal Cr/NAA appears to be more sensitive to verbal memory function than volumes.