Longitudinal Comparison of Two Severities of Unilateral Cervical Spinal Cord Injury Using Magnetic Resonance Imaging in Rats

Abstract

Magnetic resonance imaging (MRI) should be a powerful tool for characterization of spinal cord pathology in animal models. We evaluated the utility of medium-field MRI for the longitudinal assessment of progression of spinal cord injury (SCI) in a rat model. Thirteen adult rats were subjected to a 6.25 or 25 g-cm unilateral cervical SCI, and underwent MRI and behavioral tests during a 3-week study period. MRI was also performed post-mortem. Quantification of cord swelling, hypointense and hyperintense signal, and lesion length were the most valuable parameters to determine and were highly correlated to behavioral and histopathological measures. Immediately after injury, MRI showed loss of gray matter-white matter differentiation, presence of scattered hyperintense signal and local hypointense signal, and cord swelling in both groups. At 7 days after injury, the spinal cord in the 25 g-cm group was significantly larger than that of the 6.25 g-cm group (p = 0.02). Contrast enhancement of the lesion was seen at 24 h in the 6.25 g-cm group, and at 24 h and 7 days in the 25 g-cm group. The volume of hypointense signal, representing hemorrhage, throughout the lesion region was significantly larger in the 25 g-cm compared to the 6.25 g-cm group at both 14 and 21 days after SCI (p, </= 0.04). The appearance of the scattered hyperintense signal, initially representing edema, at later time points changed to a rim of hyperintense signal surrounding the lesion cavity. Significant correlations were found between cord swelling at 7 days after SCI, and lesion length and gray and white matter sparing as determined by histopathology. Other parameters that were highly correlated with histopathology were quantity of hyperintense and hypointense signal, and in vivo lesion length. Hypointense signal and in vivo lesion length were highly correlated to behavior. Significant correlation was also found between parameters determined by MRI: swelling, hypointense signal, hyperintense signal, and lesion length. MRI is a valuable imaging modality to assess the temporal evolution of SCI and to distinguish different severities of cervical SCI in rats. In future, MRI could be applied as a screening tool to either administer goal-directed therapies, or enable even group distribution, prior to therapeutic intervention for example through quantification and matching of swelling and edema.

Effect of Vascular Endothelial Growth Factor Treatment in Experimental Traumatic Spinal Cord Injury:In VivoLongitudinal Assessment

“…There were no significant differences in performance between the injured groups on these assays, and all animals improved over time, while showing a simultaneous reduction in hyperintense lesion volume. Studies have shown that edema can remain in the tissue for over 2 weeks after SCI (Demediuk et al, 1987;Mihai et al, 2008;Nolan, 1969;Sharma, 2005), and it is known that a relationship between edema and cord swelling exists (Mihai et al, 2008). The improved performance on behavioral tasks in our study was likely due to a reduction in spinal cord swelling and pressure on the fiber tracts.…”

Quantitative magnetic resonance imaging in a naturally occurring canine model of spinal cord injury

“…[2][3][4] High T2 signal intensity within the spinal cord following injury is correlated with identifiable edema, necrosis, cellular infiltrates and hemorrhage. 5,6 The presence of such lesions has been associated with slowed recovery across a number of model systems and in humans. 2,7,8 More recently, spinal cord lesion volume as measured by MRI has been used to quantitatively characterize SCI following clinical interventions.…”

Intramedullary Lesion Length on Postoperative Magnetic Resonance Imaging is a Strong Predictor of ASIA Impairment Scale Grade Conversion Following Decompressive Surgery in Cervical Spinal Cord Injury

“…18–21 In both preclinical models of SCI and clinical investigations, there is a significant relationship between the severity of SCI, neurological recovery, and the intensity of the hemorrhagic signal on theMRI. 18,19,22–27 Depending on the SCI severity, the rate of expansion of the IML in cervical SCI measures from 200 μ m/h in AIS grade C patients to 900 μ m/h in AIS grade A and B patients. 28,29 …”