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AJNR - American Journal of Neuroradiology

Published ahead of print on May 1, 2008
doi: 10.3174/ajnr.A1101

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American Journal of Neuroradiology 29:1329-1334, August 2008
© 2008 American Society of Neuroradiology

BRAIN

Diffusion Tensor Tractography of the Meyer Loop in Cases of Temporal Lobe Resection for Temporal Lobe Epilepsy: Correlation between Postsurgical Visual Field Defect and Anterior Limit of Meyer Loop on Tractography

T. Taoka^a, M. Sakamoto^a, H. Nakagawa^a, H. Nakase^b, S. Iwasaki^a, K. Takayama^a, K. Taoka^c, T. Hoshida^b, T. Sakaki^b and K. Kichikawa^a

^a Departments of Radiology, Nara Medical University, Nara Japan
^b Departments of Neurosurgery, Nara Medical University, Nara Japan
^c Department of Ophthalmology, Kakogawa Municipal Hospital, Hyogo, Japan

Please address correspondence to Toshiaki Taoka, MD, Department of Radiology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara, 634-8522, Japan; e-mail: ttaoka{at}naramed-u.ac.jp

BACKGROUND AND PURPOSE: Visual field defects sometimes occur after temporal resection surgery. Our purpose was to evaluate the correlation between visual field defects caused by temporal lobe resection and the degree of resection of the Meyer loop, as assessed by diffusion tensor tractography.

MATERIALS AND METHODS: We examined 14 patients who underwent temporal resection for temporal lobe epilepsy. We obtained presurgical tractographies and then measured the distance between the temporal tip and the anterior limit of the Meyer loop (T-M distance). The degree of resection of the Meyer loop was defined as the distance from the anterior limit of the Meyer loop to the posterior limit of the temporal lobe resection (M-R distance). This was calculated by subtracting the T-M distance from the measured distance between the temporal tip and the posterior limit of the resection (T-R distance).

RESULTS: The mean T-M distance was 36.6 mm. The interindividual variation of the distance ranged from 30.0 to 43.2 mm. Although there was no statistically significant correlation between the extent of the visual field defect and the T-R distance, there was a statistically significant correlation between the degree of the visual field defect and the M-R distance.

CONCLUSION: The range of interindividual variation for the position of the Meyer loop was rather large, indicating that this variation is the key factor in visual field defects after temporal lobectomy, and the visual field defect appears to be predicted by presurgical tractography. Evaluation of the Meyer loop through the use of tractography seems to be a feasible method, which can be used to predict the visual field defect after temporal lobe resection.

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