Time course of postoperative recovery of N-acetyl-aspartate in temporal lobe epilepsy

Purpose: To assess the time course of increases in N-acetyl-aspartate/creat ine (NAA/Cr), which can be measured using proton MR spectroscopic imaging ( H-1-MRSI). in patients with intractable nonlesional temporal robe epilepsy (TLE) after successful epilepsy surgery. Methods: We performed pre- and postoperative H-1-MRSI in 16 seizure-free (S F) patients and 16 not seizure-free (NSF) TLE patients. We calculated a mix ed-design analysis of variance (ANOVA) between SF and NSF groups, ipsi- and contralateral to the side of operation, and pre- and postoperative NAA/Cr measurements. We applied nonlinear regression be tween pre- and postoperati ve NAA/Cr differences and the time interval between H-1-MRSI scans to fit a negative exponential model to NAA recovery. Results: Mixed-design ANOVA revealed that (a) postoperative NAA/Cr was sign ificantly higher in SF than in NSF patients (p = 0.02) and that (b) in the SF group. postoperative NAA/Cr values were significantly higher than preope rative values (p < 0.05) and returned to the normal range in most patients. According to our nonlinear regression model, in SF patients, there was a 5 0% increase relative to preoperative NAA/Cr values after 5.8 months, wherea s an improvement of 95% was reached after 25 months. Conclusions: Our results extend preliminary observations of postoperative N AA recovery of SF patients by characterizing the time course of recovery as an exponential function with a half-time of <similar to>6 months. The reve rsal of neuronal metabolic dysfunction remote from the epileptic focus may underlie the clinical observation of improvement of cognitive dysfunction a fter successful epilepsy surgery.