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.
Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, Canada, H3A 2B4.
W
W
Serles
L M
LM
Li
S B
SB
Antel
F
F
Cendes
J
J
Gotman
A
A
Olivier
F
F
Andermann
F
F
Dubeau
D L
DL
Arnold
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