Evaluation of Hyperbaric Oxygen Treatment in Acute Traumatic Spinal Cord Injury in Rats Using Diffusion Tensor Imaging

Abstract

This study aimed to evaluate the therapeutic effect of hyperbaric oxygen (HBO) on acute spinal cord injury (SCI) by measuring the in vivo diffusion tensor imaging (DTI) parameters apparent diffusion coefficient (ADC) and fractional anisotropy (FA) and observing diffusion tensor tractography (DTT) of fiber bundle morphology. The rats were randomly divided into sham-operated (SH), SCI, and SCI and hyperbaric oxygen treatment (SCI + HBO) groups (n = 6 in each group). The Basso-Bettie-Bresnahan (BBB) score was used to evaluate motor function recovery, and DTI was performed on days 3, 7, 14, and 21 after surgery. BBB scores and FA values decreased significantly after SCI, while the two values significantly improved in the SCI + HBO group compared with the SCI group on days 7, 14, and 21. ADC increased significantly on days 14 and 21 postoperatively in the SCI group compared with the SH group but did not significantly differ between the SCI and SCI + HBO groups at any time point. BBB scores had the same variation trend with ADC values and FA values in all three groups. In the SH group, DTT showed a well-organized spinal cord, but the spinal cord showed interruptions at sites of injury after SCI. In conclusion, HBO promotes the recovery of neuronal function after SCI. Parameters of DTI, especially FA, can quantitatively evaluate the efficacy of HBO treatment in SCI, while DTT enables the visualization of the fiber tracking of spinal cord tracts.

Keywords: diffusion tensor imaging; hyperbaric oxygen; spinal cord injury.

Figure 1.

BBB scores for hind limb motor function in each group at different time points. The values are expressed as mean ± SD. **P < 0.001, *P < 0.01.

Figure 2.

Conventional magnetic resonance images from the SH, SCI, and SCI + HBO groups at different time points. T1WI and T2WI in the SH group showed normal signal intensity at all time points (A, D, G, L). T1WI depicted less noticeable changes of the signal intensity after surgery, it still revealed the location of spinal cord lesions (A-L). T2WI of injured groups showed hypointense region within the central cord parenchyma surrounding a hyperintense region corresponding to the site of contusion on day 3 after SCI (B, C). Over time, the hypointense region faded away, while the hyperintense region became more noticeable (E, F, H, I, K, L).

Figure 3.

ADC and FA images in each group at different time points.

Figure 4.

FA and ADC values of rats in the three groups. (A) FA values measured in the SH, SCI, SCI + HBO groups. (B) ADC values measured in the SH, SCI, and SCI + HBO groups. Values are expressed as mean ± SD. *P < 0.05, #P < 0.01.

Figure 5.

FA and ADC values of rats at different time points. (A) FA values measured in the SH, SCI, and SCI + HBO groups. (B) ADC values measured in the SH, SCI, and SCI + HBO groups.

Figure 6.

Variation trend of DTI results and BBB scores. (A) In all three groups (SH, SCI, and SCI + HBO), BBB scores and ADC values had the same variation trend after the Mann-Kendall trend test. (B) The same variation trend was found between the BBB score and the FA value.

Figure 7.

DTT of the three groups at different time points. DTT showed a continuous and intact spinal cord in uninjured rats (A, D, G, L); however, after SCI, the rats showed interrupted DTT (B, C). Over time, the spinal cord tracts in the injured groups gradually became continuous, with the tracts in the SCI + HBO group showing better continuity than the tracts in the SCI group at all time points (E, F, H, I, K, L).