Correlation of diffusion tensor imaging and phase-contrast MR with clinical parameters of cervical spinal cord injuries

Abstract

Study design: This is a cross-sectional study. Objectives: The goal of this study was to characterize the diffusion properties across segments of the spinal cord and peak cerebrospinal fluid (CSF) velocities in the stenotic spinal canal, and to determine the correlation between these properties and clinical and electrophysiological parameters in patients with cervical spinal cord injury (SCI). Setting: This study was conducted in the University teaching hospital. Methods: The study involved 17 patients with cervical SCI. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) of the spinal cord and peak systolic and diastolic velocities of CSF were measured at the level of maximum compression (region 1) and at the levels above (region 2) and below (region 3) the level of injury with no signal change in conventional magnetic resonance imaging. Neurological and electrophysiological parameters were measured, including American Spinal Injury Association (ASIA) Impairment Scale (AIS), ASIA motor score, ASIA sensory score, Modified Barthel Index, Spinal Cord Independence Measure III (SCIM III), somatosensory evoked potentials (SSEP) and motor evoked potentials (MEP). Results: The ADC was significantly higher and the FA was significantly lower in regions 1, 2 and 3 of the SCI patients than in the normal controls (Po0.05 each). FA of the level below correlated with AIS, ASIA sensory score and SCIM III score, and FA of the level above correlated with SSEP latencies and MEP amplitudes (Po0.05 each). The reductions in FA correlated with CSF flow, functional measurements and evoked potentials. INTRODUCTIONOwing to its high soft-tissue resolution, conventional magnetic resonance imaging (MRI) is used routinely in the diagnosis of spinal cord injury (SCI). However, conventional MRI has low sensitivity for diffusion abnormalities in the white matter, limiting the associations between MRI results and clinical status. 1,2 Diffusion tensor imaging (DTI) with fiber tractography provides a threedimensional model of water diffusion for longitudinal evaluations of the central nervous system. 3 Although the application of DTI to the human spinal cord is challenging technically, owing to the small cross-sectional area of the spinal cord, cardiac and respiratory motion, and widely varying magnetic susceptibility, 4 recent developments in magnetic resonance (MR) pulse sequence design have greatly reduced these problems. Moreover, phase-contrast MRI (PC-MRI) is a noninvasive technique that can be used to quantify variations in the flow of the cerebrospinal fluid (CSF) gated with the cardiac cycle. 5 CSF flow can be influenced by stenotic lesions in the brain and spinal cord. 6,7 Initially, SCI results in the physical disruption of structures in the spinal cord (primary insult), and it might also induce secondary events that injure intact, neighboring tissues in the epidural, subdural,

Subject-specific regional measures of water diffusion are associated with impairment in chronic spinal cord injury

“…The significant changes in FA AL and RD AL observed in individuals with chronic SCI (Table 3) are also in agreement with the previous findings. Similarly, the observed significant correlation between functional impairment and the values of the DTI indices is in accordance with previous studies [11, 14, 17, 23], where lower FA and higher AD and RD values are reported to be correlated with worse ISNCSCI scores.…”

“…Notably, we observed that compared to FA AL , FA IRRI showed stronger correlation with ISNCSCI-tot, which is in accordance with a previous study [17] – indicating that subject-specific regional measures of FA, and in particular, those measured from IRRI-region, may be more specific to impairment. A similar trend of stronger correlations between ISNCSCI-tot and other IRRI-region DTI indices, specifically RD IRRI and AD IRRI , was also observed (Table 4).…”

“…Methods for spinal cord segmentation can be broadly categorized as manual, automated, and semi-automated. Although most time-consuming, the manual segmentation [11, 15–17] is highly accurate. However, application of the fully automated methods [18–21] in clinical environment is complicated by the small size of the spinal cord that often leads to low-resolution images that are suboptimal for fully automated segmentation.…”

“…However, those methods are also potentially less sensitive to pathological changes, due to extensive averaging of DTI index values over regions of healthy spinal cord. Such regional averaging can be minimized by placing the ROIs in regions that are subject- and injury-region-specific, reflecting the varying levels and sizes of lesion in each individual [17, 24, 25].…”

Filter‐probe diffusion imaging improves spinal cord injury outcome prediction

“…Current clinical standards rely on functional testing, such as American Spinal Injury Association scoring for characterizing injury, but are often unreliable for predicting long‐term functional outcomes due to changes in score over time within some patients . Clinical magnetic resonance imaging (MRI), such as T 2 ‐weighted imaging, has aided SCI assessment, but similarly does not reliably predict long‐term functional outcomes due to the lack of specificity to axonal damage, the strongest pathological correlate of long‐term functional outcome following SCI . Thus, techniques such as diffusion‐weighted imaging (DWI), and diffusion tensor imaging (DTI) in particular, have garnered considerable interest as noninvasive biomarkers of SCI due to their sensitivity to microscopic axonal damage …”