Changes in fiber tract integrity and visual fields after anterior temporal lobectomy.
OBJECTIVE
To investigate postoperative changes in fiber tract integrity in patients with temporal lobe epilepsy (TLE) following anterior temporal lobectomy (ATL) and to determine whether postoperative changes are 1) stable vs progressive and 2) related to visual field defects.


METHODS
Diffusion tensor imaging (DTI) was obtained in 7 patients with TLE before, 2 months after, and 1 year after ATL. Changes in fractional anisotropy (FA) were evaluated in a whole-brain voxel-wise analysis, as well within specific fiber tracts. Repeated-measures analysis of variance was performed to examine the time course of FA changes within ipsilateral and contralateral fiber tracts. Quantitative visual field analysis was performed to determine whether decreases in regional FA were related to the extent or location of visual field defects.


RESULTS
Patients showed decreased FA 2 months post-ATL in ipsilateral fiber tracts transected during surgery (parahippocampal cingulum, uncinate fasciculus, inferior longitudinal fasciculus, and fornix), as well as in fiber tracts not directly transected (inferior fronto-occipital fasciculus and corpus callosum). Additional decreases in FA were not observed from 2 months to 1 year post-ATL. Visual field defects in most patients were characterized by incomplete quadrantanopsias. However, FA reductions in one patient extended into temporo-occipital cortex and the splenium of the corpus callosum and were associated with a complete hemianopia.


CONCLUSIONS
Wallerian degeneration is apparent 2 months following unilateral ATLs in ipsilateral fibers directly and indirectly affected during surgery. These changes do not appear to progress over the course of a year, but may correlate with the nature and extent of postoperative visual field defects.
McDonald
C R
CR
Department of Psychiatry, Multimodal Imaging Laboratory, University of California-San Diego, 8950 Villa La Jolla Drive, La Jolla, CA 92037, USA. camcdonald@ucsd.edu
Hagler
D J
DJ
Girard
H M
HM
Pung
C
C
Ahmadi
M E
ME
Holland
D
D
Patel
R H
RH
Barba
D
D
Tecoma
E S
ES
Iragui
V J
VJ
Halgren
E
E
Dale
A M
AM
D000328:Adult; D016880:Anisotropy; D038481:Anterior Temporal Lobectomy / Q000379:methods*; D001931:Brain Mapping; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D001330:Electronic Data Processing; D004833:Epilepsy, Temporal Lobe / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D013997:Time Factors; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult