Effects of illness duration on memory processing of patients with temporal lobe epilepsy.
OBJECTIVE
To examine the effects of illness duration on the neural processing of memory in patients with temporal lobe epilepsy (TLE) by using functional MRI.


METHODS
Twenty-three TLE patients (16 left, seven right) performed a complex visual scene-encoding task during functional MRI. Region-of-interest (ROI) analyses were used to quantity functional activation in the mesial temporal and frontal lobes. The patients' verbal and visual memory performances were evaluated by standardized neuropsychological tests. Analyses included group comparison and correlations of duration of epilepsy with functional activation and memory performance.


RESULTS
Compared with normal controls, TLE patients demonstrated reduced activation bilaterally in the mesial temporal lobe (p=0.003), and the reduction was more pronounced on the ipsilateral side of the seizure focus. Moreover, a longer duration of illness was associated with fewer voxels activated in both the left (p=0.038) and right (p=0.017) mesial temporal lobe. Furthermore, the duration of illness was found to be significantly and negatively correlated with both verbal (p=0.020) and visual (p=0.000) memory functioning.


CONCLUSIONS
TLE seems to affect the memory processes in the mesial temporal lobes progressively (i.e., the longer the duration of illness, the lower the brain activation). In turn, the reduction of brain activation negatively affects memory functioning. Finally, the reduction is not limited to the side of seizure but also is observed in the contralateral hemisphere.
Cheung
Mei-chun
MC
Department of Psychology, The Chinese University of Hong Kong, Hong Kong SAR.
Chan
Agnes S
AS
Chan
Yu-leung
YL
Lam
Joseph M K
JM
Lam
Wan
W
D000293:Adolescent; D000328:Adult; D000654:Amobarbital / Q000494:pharmacology; D001037:Aphasia / Q000139:chemically induced; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008568:Memory / Q000502:physiology; D008569:Memory Disorders / Q000175:diagnosis* / Q000503:physiopathology; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011597:Psychomotor Performance / Q000502:physiology; D013702:Temporal Lobe / Q000502:physiology / Q000503:physiopathology*; D013997:Time Factors; D014705:Verbal Behavior / Q000502:physiology; D014796:Visual Perception / Q000502:physiology
D000654:Amobarbital