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Diffusion tensor imaging in cases with visual field defect after anterior temporal lobectomy.
Toshiaki Taoka1, Masahiko Sakamoto, Satoru Iwasaki
1Department of Radiology, Nara Medical University, Kashihara, Nara, Japan.
AJNR. American Journal of Neuroradiology
|April 9, 2005
Summary
Diffusion tensor imaging (DTI) can detect optic radiation injury after temporal lobectomy. Fractional anisotropy (FA) decreases with visual defect severity, indicating Wallerian degeneration, while apparent diffusion coefficient (ADC) changes later.
Area of Science:
- Neuroimaging
- Neuroradiology
- Neuroscience
Background:
- Temporal lobectomy for epilepsy can cause visual defects due to optic radiation injury.
- Diffusion tensor imaging (DTI) is a valuable tool for assessing white matter integrity.
Purpose of the Study:
- To investigate DTI's ability to detect optic radiation changes post-temporal lobectomy.
- To correlate DTI parameters with the severity of visual field defects.
Main Methods:
- 14 patients undergoing temporal lobectomy were studied.
- Diffusion tensor imaging parameters, including fractional anisotropy (FA) and apparent diffusion coefficient (ADC), were measured.
- Patients were grouped by visual field defect severity (A-C).
Main Results:
- Decreased FA ratios in operated optic radiations correlated with visual defect severity.
- High signal intensities on T2-weighted images were observed in later stages (>4 weeks post-surgery).
- ADC ratios showed a trend of increase in later stages (>10 weeks post-surgery) with increasing visual defect.
Conclusions:
- Reduced FA in optic radiations after temporal lobectomy indicates Wallerian degeneration.
- DTI, particularly FA, can evaluate early-stage optic radiation degeneration.
- ADC changes may reflect later stages of injury and gliosis.