Defining Meyer's loop–temporal lobe resections, visual field deficits and diffusion tensor tractography
Yogarajah M et al. – Findings show considerable variation in the anterior extent of Meyer's loop. Thus, diffusion tensor tractography of optic radiation is a potentially useful method to assess an individual pt's risk of postoperative visual field deficits (VFDs) after anterior temporal lobe resection. Methods- Use of seed voxels antero-lateral to lateral geniculate nucleus for diffusion tensor tractography as an advanced magnetic resonance imaging technique to enable white matter parcellation
- Evaluation of 20 controls and 21 postoperative pts
- Assessment with Goldmann perimetry of visual fields >3 mo after surgery
- Measurement of distance from tip of Meyer's loop to temporal pole and horn
- Measurement of size of temporal lobe resection by postoperative T1-weighted images
- Quantification of VFDs
Results- VFDs in 9 pts, ranging from 22% to 87% of contralateral superior quadrant
- Range of distance from tip of Meyer's loop to temporal pole: 24–43 mm (mean 34 mm) for pts vs 24–47 mm (mean 35 mm) for controls
- Pt range of distance from tip of Meyer's loop to temporal horn: –15 to +9 mm (mean 0 mm) vs –11 to +9 mm (mean 0 mm) for controls
- Both quantitative and qualitative results agreed with recent dissections of cadaveric brains, and analysis of postoperative VFDs and resection volumes
- On linear regression analysis, both distance from tip of Meyer's loop to temporal pole and resection size were significant predictors of postoperative VFDs
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