Time course of postoperative recovery of N-acetyl-aspartate in temporal lobe epilepsy.
OBJECTIVE
To assess the time course of increases in N-acetyl-aspartate/creatine (NAA/Cr), which can be measured using proton MR spectroscopic imaging (1H-MRSI), in patients with intractable nonlesional temporal lobe epilepsy (TLE) after successful epilepsy surgery.


METHODS
We performed pre- and postoperative 1H-MRSI in 16 seizure-free (SF) patients and 16 not seizure-free (NSF) TLE patients. We calculated a mixed-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 between pre- and postoperative NAA/Cr differences and the time interval between 1H-MRSI scans to fit a negative exponential model to NAA recovery.


RESULTS
Mixed-design ANOVA revealed that (a) postoperative NAA/Cr was significantly 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 preoperative 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 50% increase relative to preoperative NAA/Cr values after 5.8 months, whereas an improvement of 95% was reached after 25 months.


CONCLUSIONS
Our results extend preliminary observations of postoperative NAA recovery of SF patients by characterizing the time course of recovery as an exponential function with a half-time of approximately 6 months. The reversal of neuronal metabolic dysfunction remote from the epileptic focus may underlie the clinical observation of improvement of cognitive dysfunction after successful epilepsy surgery.
Serles
W
W
Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada, H3A 2B4.
Li
L M
LM
Antel
S B
SB
Cendes
F
F
Gotman
J
J
Olivier
A
A
Andermann
F
F
Dubeau
F
F
Arnold
D L
DL
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis*; D003401:Creatine / Q000032:analysis; D004833:Epilepsy, Temporal Lobe / Q000378:metabolism / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D016014:Linear Models; D009682:Magnetic Resonance Spectroscopy / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D012044:Regression Analysis; D013702:Temporal Lobe / Q000737:chemistry* / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome
D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine