In VivoLongitudinal MRI and Behavioral Studies in Experimental Spinal Cord Injury

Abstract

Comprehensive in vivo longitudinal studies that include multi-modal magnetic resonance imaging (MRI) and a battery of behavioral assays to assess functional outcome were performed at multiple time points up to 56 days post-traumatic spinal cord injury (SCI) in rodents. The MRI studies included high-resolution structural imaging for lesion volumetry, and diffusion tensor imaging (DTI) for probing the white matter integrity. The behavioral assays included open-field locomotion, grid walking, inclined plane, computerized activity box performance, and von Frey filament tests. Additionally, end-point histology was assessed for correlation with both the MRI and behavioral data. The temporal patterns of the lesions were documented on structural MRI. DTI studies showed significant changes in white matter that is proximal to the injury epicenter and persisted to day 56. White matter in regions up to 1 cm away from the injury epicenter that appeared normal on conventional MRI also exhibited changes that were indicative of tissue damage, suggesting that DTI is a more sensitive measure of the evolving injury. Correlations between DTI and histology after SCI could not be firmly established, suggesting that injury causes complex pathological changes in multiple tissue components that affect the DTI measures. Histological evidence confirmed a significant decrease in myelin and oligodendrocyte presence 56 days post-SCI. Multiple assays to evaluate aspects of functional recovery correlated with histology and DTI measures, suggesting that damage to specific white matter tracts can be assessed and tracked longitudinally after SCI.

Different magnetic resonance imaging patterns after transcranial magnetic resonance–guided focused ultrasound of the ventral intermediate nucleus of the thalamus and anterior limb of the internal capsule in patients with essential tremor or obsessive-compulsive disorder

“…Consistent with this possibility, a previous study in rats showed noticeably absent myelin and oligodendrocytes in injured brain areas 1 week after injury, with these changes persisting for up to 56 days. 24 Because MRgFUS is a closed-loop procedure, neurological function and also the site and size of lesions can be monitored during treatment using MRI. During thalamotomy for ET patients, we monitored hand tremors, sensory changes, and motor function.…”

Ex Vivo Diffusion Tensor Imaging of Spinal Cord Injury in Rats of Varying Degrees of Severity

“…41 Changes in water balance are thought to greatly affect the diffusion of water within tissue. 2,11,42 The significant decrease in the diffusion values for MD, LD, and RD appear to suggest that the changes to the cellular fluidic environment could be a direct cause of the changes to water diffusion; however, further investigation into the water volume shift between intracellular and extracellular compartments is needed.…”

“…There has been a persistent interest in imaging specific tracts of the spinal cord following an injury in order to ascertain whether functional outcomes might be associated with particular tract loss. 2,3,12 As such, there has been a desire to obtain improved resolution images with higher SNR. [47][48][49] The current study benefited in this regard from the use of ex vivo scans; however, additional resolution and improved SNR might be obtained with new coil designs and improved image sequences.…”

“…As diffusion barriers within the tissue change after injury, DTI has provided researchers with an invaluable tool to monitor histological changes to the spinal cord after a spinal cord injury (SCI); however, most studies have focused on diffusion measurements at or within a few segments of the site of injury. [1][2][3] Although DTI at the injury site provides information about the histological structure of the injured spinal cord, imaging of the injury site after trauma in humans can be challenging. After injury, the spine tissues are disrupted, and stabilization devices are typically placed around the lesion site, which causes imaging artifacts in an MRI and prevents a physician from assessing the severity of an injury.…”

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

“…A 11 · 35-mm rectangular radio frequency (RF) coil was implanted over the spinal column, centered on the site of injury (Deo et al, 2006;Fenyes and Narayana, 1998;Sundberg et al, 2010), held in place with two sutures, and tuned to the operating frequency of the MRI scanner. The overlying muscles were sutured and the skin was closed.…”