ORIGINAL ARTICLE
In Vivo Evaluation of Sciatic Nerve Crush Injury Using Diffusion Tensor Imaging: Correlation With Nerve Function and Histology Chongpeng Sun, MD, PhD,* Zhongjun Hou, MS,† Guobin Hong, MD, PhD,‡ Qi Wan, MS,* and Xinchun Li, MD, PhD* Objective: The aim of this study was to prospectively estimate magnetic resonance diffusion tensor imaging parameters in distal portions of crushed sciatic nerves in rabbits and correlation with neurological function and histology. Methods: Thirty-two rabbits were randomly divided into 8 groups and followed up at 10 weeks. The right sciatic nerves were crushed, and the left sciatic nerves served as the control group with sham operation. Another 4 rabbits were chosen in the normal control group. Diffusion tensor imaging scan was obtained on bilateral sciatic nerves using spin-echo singleshot echo planar imaging. The values of fractional anisotropy (FA), apparent diffusion coefficient, and eigenvalue (λ║ and λ⊥) were measured on diffusion tensor imaging. Quantitative assessment of functional recovery in crushed nerves included toe-spreading reflex and modified Tarlov score, as well as pathology of the injured nerves. Results: Fractional anisotropy of distal portions in injured nerves reduced slightly on the first day and dropped to the minimum at the fourth day after surgery. Then, FA increased gradually from the eighth day to the eighth week. After that, FA recovered nearly normal in the 10th week after injury. There was statistical significance in FA during 4 days to the eighth week and λ⊥ values between distal portions of injured nerves and normal control nerves (P < 0.05). Fractional anisotropy of distal portions to injured nerves correlated significantly with the nerve function score(r = 0.898, P < 0.01), whereas λ⊥ of distal portions of injured nerves demonstrated negative correlation with the nerve function score(r = −0.820, 0.05). Also, no significant difference could be found between FA, ADC, λ║, and λ⊥ of the sham-operated nerves and normal control nerves (P > 0.05). Fractional anisotropy, ADC, λ║, and λ⊥ values time curve is summarized in Figure 4.
Functional Recovery Marked impairment of sciatic nerves of the injured hind limb was observed on the first day after the injury. Those showed obvious functional deficit from the fourth day to the eighth day after surgery, recovered gradually from the second week to the eighth week, and reached to nearly normal in the 10th week in this
TABLE 1. Function Assessment With Time After Crush Injury Toe-Spreading Reflex
Tarlov Scale
Follow-up Interval
I
II
III
IV
0
1
2
3
4
Total Score
0d 1d 4d 8d 2 wk 4 wk 6 wk 8 wk 10 wk
0 4 4 4 4 3 1 0 0
0 0 0 0 0 1 3 1 0
0 0 0 0 0 0 0 2 2
4 0 0 0 0 0 0 1 2
0 0 0 0 0 0 0 0 0
0 2 1 1 0 0 0 0 0
0 2 3 3 3 1 0 0 0
0 0 0 0 1 3 4 2 0
4 0 0 0 0 0 0 2 4
32 10 11 11 13 14 19 26 30
Data represent the numbers of animals. There are 4 rabbits observed at different time points. Functional impairment was not found in the sham-operated nerves as these data were not included.
© 2014 Lippincott Williams & Wilkins
www.jcat.org
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
793
J Comput Assist Tomogr • Volume 38, Number 5, September/October 2014
Sun et al
experimental model. No significant functional impairment was observed in the sham-operated limbs and normal control limbs. Functional assessments in the injured nerves are summarized in Table 1.
Correlations Between DTI Parameters and Nerve Function Score We correlated the changes in FA and λ⊥ of the distal portion in injured nerves with functional recovery. In contrast to normal controls and sham-operated nerves, we found that FA positively correlated with nerve function score(r = 0.898, P < 0.01) in injured nerves (Fig. 5A). On the contrary, λ⊥ was negatively correlated with nerve function(r = −0.820,
In Vivo Evaluation of Sciatic Nerve Crush Injury Using Diffusion Tensor Imaging: Correlation With Nerve Function and Histology Chongpeng Sun, MD, PhD,* Zhongjun Hou, MS,† Guobin Hong, MD, PhD,‡ Qi Wan, MS,* and Xinchun Li, MD, PhD* Objective: The aim of this study was to prospectively estimate magnetic resonance diffusion tensor imaging parameters in distal portions of crushed sciatic nerves in rabbits and correlation with neurological function and histology. Methods: Thirty-two rabbits were randomly divided into 8 groups and followed up at 10 weeks. The right sciatic nerves were crushed, and the left sciatic nerves served as the control group with sham operation. Another 4 rabbits were chosen in the normal control group. Diffusion tensor imaging scan was obtained on bilateral sciatic nerves using spin-echo singleshot echo planar imaging. The values of fractional anisotropy (FA), apparent diffusion coefficient, and eigenvalue (λ║ and λ⊥) were measured on diffusion tensor imaging. Quantitative assessment of functional recovery in crushed nerves included toe-spreading reflex and modified Tarlov score, as well as pathology of the injured nerves. Results: Fractional anisotropy of distal portions in injured nerves reduced slightly on the first day and dropped to the minimum at the fourth day after surgery. Then, FA increased gradually from the eighth day to the eighth week. After that, FA recovered nearly normal in the 10th week after injury. There was statistical significance in FA during 4 days to the eighth week and λ⊥ values between distal portions of injured nerves and normal control nerves (P < 0.05). Fractional anisotropy of distal portions to injured nerves correlated significantly with the nerve function score(r = 0.898, P < 0.01), whereas λ⊥ of distal portions of injured nerves demonstrated negative correlation with the nerve function score(r = −0.820, 0.05). Also, no significant difference could be found between FA, ADC, λ║, and λ⊥ of the sham-operated nerves and normal control nerves (P > 0.05). Fractional anisotropy, ADC, λ║, and λ⊥ values time curve is summarized in Figure 4.
Functional Recovery Marked impairment of sciatic nerves of the injured hind limb was observed on the first day after the injury. Those showed obvious functional deficit from the fourth day to the eighth day after surgery, recovered gradually from the second week to the eighth week, and reached to nearly normal in the 10th week in this
TABLE 1. Function Assessment With Time After Crush Injury Toe-Spreading Reflex
Tarlov Scale
Follow-up Interval
I
II
III
IV
0
1
2
3
4
Total Score
0d 1d 4d 8d 2 wk 4 wk 6 wk 8 wk 10 wk
0 4 4 4 4 3 1 0 0
0 0 0 0 0 1 3 1 0
0 0 0 0 0 0 0 2 2
4 0 0 0 0 0 0 1 2
0 0 0 0 0 0 0 0 0
0 2 1 1 0 0 0 0 0
0 2 3 3 3 1 0 0 0
0 0 0 0 1 3 4 2 0
4 0 0 0 0 0 0 2 4
32 10 11 11 13 14 19 26 30
Data represent the numbers of animals. There are 4 rabbits observed at different time points. Functional impairment was not found in the sham-operated nerves as these data were not included.
© 2014 Lippincott Williams & Wilkins
www.jcat.org
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
793
J Comput Assist Tomogr • Volume 38, Number 5, September/October 2014
Sun et al
experimental model. No significant functional impairment was observed in the sham-operated limbs and normal control limbs. Functional assessments in the injured nerves are summarized in Table 1.
Correlations Between DTI Parameters and Nerve Function Score We correlated the changes in FA and λ⊥ of the distal portion in injured nerves with functional recovery. In contrast to normal controls and sham-operated nerves, we found that FA positively correlated with nerve function score(r = 0.898, P < 0.01) in injured nerves (Fig. 5A). On the contrary, λ⊥ was negatively correlated with nerve function(r = −0.820,
