Diffusion Tensor Imaging in Cases with Visual Field Defect after Anterior Temporal Lobectomy
Toshiaki Taokaa,
Masahiko Sakamotoa,
Satoru Iwasakic,
Hiroyuki Nakagawaa,
Akio Fukusumia,
Shinji Hirohashia,
Keiko Taokad,
Kimihiko Kichikawaa,
Tohru Hoshidab and
Toshisuke Sakakib
a Department of Radiology, Nara Medical University, Nara, Japan
b Department of Neurosurgery, Nara Medical University, Nara, Japan
c Department of Radiology, Higashiosaka City General Hospital, Higashiosaka, Japan
d Department of Ophthalmology, Kobe University, Hyogo, Japan
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FIG 1. Schematic drawing of the classification by visual field defect. Anterior fibers of Meyer’s loop correspond to the medial sector and posterior fibers correspond to lateral sectors of the upper quadrant visual field of the contralateral side.
Group A, incomplete defect in the medial sector of the upper quadrant visual field.
Group B, complete defect in the medial sector and incomplete defect within the lateral sector.
Group C, complete defect in both the medial and lateral sectors.
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FIG 2. Case 1, a 23-year-old man.
A and B, T2-weighted images. The patient had a left temporal lobectomy (A). No abnormal signal intensity is seen within the sagittal stratum, which includes optic radiation (B). C, Visual field: Partial visual field defect in the medial sector is seen (group A). D, Color-displayed tensor image: Sagittal strata including the optic radiation are recognized as a green area indicating an anterior to posterior directed tract. Regions of interest for measurement are shown as dotted lines. E, FA image 255 . FA of the left optic radiation shows a slightly lower value as compared with the opposite side (right, 0.499; left, 0.425). F, ADC image 255 . There is no apparent difference between the optic radiations of both sides (right, 5.90 x 10 –4 mm2/s; left, 5.70 x 10–4 mm2/s).
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FIG 3. Case 9, a 44-year-old man.
A and B, T2-weighted image. The patient had a left temporal lobectomy (A). No abnormal signal intensity can be seen along the sagittal stratum (B). C, Visual field. The medial sector of the upper quadrant visual field is completely impaired, and partial impairment in the lateral sector area can be seen. D, Color-displayed tensor image. Sagittal strata are recognized as a green area, which indicates an anterior to posterior directed tract. Regions of interest for measurement of ADC and FA values are shown as dotted lines. E, FA image. The FA value of the left optic radiation shows a lower value as compared with the opposite side (right, 0.526; left, 0.488). F, ADC image. There is no apparent difference between the optic radiations of both sides (right, 6.20 x 10–4 mm2/s; left, 6.10 x 10–4 mm2/s).
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FIG 4. Case 8, a 49-year-old man.
A and B, T2-weighted image. The patient had left anterior temporal lobectomy (A), and there is a high signal intensity area in the anterior part of left sagittal stratum (B, arrow). C, Visual field. The upper quadrant visual field is completely impaired. D, Color-displayed tensor image. Sagittal strata including the optic radiation were recognized as a green area even in operated side. Regions of interest for measurement are shown as dotted lines. E, FA image. The FA value of the left sagittal strata shows a noticeably lower value as compared with the opposite side (right, 0.506; left, 0. 394). F, ADC image. No apparent difference between the optic radiations of both sides is observed (right, 6.10 x 10–4 mm2/s; left, 7.00 x 10–4 mm2/s).
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FIG 5. A, FA values for the lobectomy and intact side in groups A, B, and C. The FA value of the lobectomy side shows a lower value compared with the intact side in each group. There are statistically significant differences between the operated and intact side in group A (P < .05), group B (P < .01) and C (P < .01). B, ADC values for the lobectomy and intact side in groups A, B, and C. There is no statistical difference between the ADC value of the operative side and intact side when evaluated overall.
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FIG 6. A, Mean operated-to-intact side FA ratio. The mean operated-to-intact side FA ratio in the sagittal strata is shown. The more severe groups show a smaller FA in the operated side. Groups A and C, and groups B and C showed statistically significant differences. B, Mean operated-to-intact side ADC ratio. The mean operated-to-intact side ADC ratio in the sagittal strata is shown. There is no statistically significant difference between the three groups when evaluated overall.
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FIG 7. A, The mean operative to intact side FA ratio as classified by the severity of visual defect and duration after surgery. The mean operated-to-intact side FA ratio as classified by visual field and duration after surgery is shown. Even in early cases after surgery, the FA value is found to decrease, and for the groups examined long after surgery, there is also an obvious decrease. There were no cases that were examined within 4–10 weeks in groups A or B. B, Mean operated-to-intact side ADC ratio as classified by the severity of visual defect and duration after surgery. Although a statistically significant difference is not detected when evaluated overall, there is a trend for the ADC value to decrease in the early period after surgery and increase during the late period after surgery. In the groups with time periods of >10 weeks after surgery, the increase of ADC is larger in group C. There were no cases that were examined within 4–10 weeks for groups A or B.
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