Midsagittal tissue bridges are associated with walking ability in incomplete spinal cord injury: A magnetic resonance imaging case series

Abstract

Context: Following spinal cord injury (SCI), early prediction of future walking ability is difficult, due to factors such as spinal shock, sedation, impending surgery, and secondary long bone fracture. Accurate, objective biomarkers used in the acute stage of SCI would inform individualized patient management and enhance both patient/family expectations and treatment outcomes. Using magnetic resonance imaging (MRI) and specifically a midsagittal T2-weighted image, the amount of tissue bridging (measured as spared spinal cord tissue) shows potential to serve as such a biomarker. Ten participants with incomplete SCI received MRI of the spinal cord. Using the midsagittal T2-weighted image, anterior and posterior tissue bridges were calculated as the distance from cerebrospinal fluid to the damage. Then, the midsagittal tissue bridge ratio was calculated as the sum of anterior and posterior tissue bridges divided by the spinal cord diameter. Each participant also performed a 6-minute walk test, where the total distance walked was measured within six minutes. Findings: The midsagittal tissue bridge ratio measure demonstrated a high level of inter-rater reliability (ICC = 0.90). Midsagittal tissue bridge ratios were significantly related to distance walked in six minutes (R = 0.68, P = 0.03). Conclusion/clinical relevance: We uniquely demonstrated that midsagittal tissue bridge ratios were correlated walking ability. These preliminary findings suggest potential for this measure to be considered a prognostic biomarker of residual walking ability following SCI.

Establishing the inter-rater reliability of spinal cord damage manual measurement using magnetic resonance imaging

“…Our results demonstrate that edema characteristics can be reliably measured, even among novice raters. In regards to the MTB measure, high levels of inter-rater reliability were found in previous literature [12,19]. Among two experienced raters, the inter-rater reliability of the axial damage ratio was previously reported as ICC = 0.82 [5], consistent with our results.…”

“…These manual measurements of spinal cord edema have been reported as important for relating to physical function [5,11,12]. In particular, MTB have shown to correlate with current and future walking ability following SCI [12,19]. Based on our results, it may be possible for clinicians, regardless of imaging experience level, to reliably measure cord edema and use this as an adjunct tool to inform prognosis and thus, clinical management.…”

“…This project was a retrospective analysis of MRI data from published studies [5,8,19]. It was approved by Northwestern University and Regis University Institutional Review Boards.…”

“…Data were collected from Northwestern University's Neuromuscular Imaging and Research Lab. MR images of 10 participants with SCI were selected based on availability from previous work [19] (nine males and one female, mean age: 44, median age: 44, standard deviation: 12, range: 27-64). In terms of severity of injury, two participants were classified using the American Spinal Cord Injury Association Impairment Scale (AIS) as AIS C C5-C8, while eight participants were classified as AIS D. Participants were included if they had sensorimotor incomplete cervical SCI with images collected after cervical fusion.…”

“…Edema length (EL) has been commonly measured and reported as the extent of edema along the cranial-caudal axis [7, 9-11, 13-15, 18]. Midsagittal tissue bridge (MTB) measures have emerged as a promising approach for functional prognosis [12,19]. The axial damage ratio (ADR) is a novel measure used to capture the two-dimensional extent of edema within the cord [5].…”