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Correlation between degree of subvoxel spinal cord compression measured with super-resolution tract density imaging and neurological impairment in cervical spondylotic myelopathy.

ABSTRACT: OBJECT The purpose of this study was to explore the use of super-resolution tract density images derived from probabilistic diffusion tensor imaging (DTI) tractography of the spinal cord as an imaging surrogate for microstructural integrity and functional impairment in patients with cervical spondylosis. METHODS Structural MRI and DTI images were collected for 27 patients with cervical spondylosis with (n= 21) and without (n= 6) functional impairment as defined by the modified Japanese Orthopaedic Association Scale (mJOA). DTI was performed axially through the site of compression in a total of 20 directions with 10 averages. Probabilistic tractography was performed at 0.5-mm isotropic spatial resolution using the streamline technique combined with constrained spherical deconvolution. The following measurements were calculated for each patient: maximum tract density at the site of compression, average tract density in rostral normal-appearing spinal cord, and the ratio of maximum density to normal density. RESULTS Compared with normal tissue, the site of compression exhibited elevated fiber tract density in all patients, and a higher fiber tract density was also noted in focal areas at the site of compression in patients with functional impairment. There was a strong negative correlation between maximum tract density and mJOA score (R(2)= 0.6324, p < 0.0001) and the ratio of maximum tract density to normal tract density (R(2)= 0.6647, p < 0.0001). When grouped according to severity of neurological impairment (asymptomatic, mJOA score of 18; mild, mJOA score of 15-17; moderate, mJOA score of 11-14; and severe, mJOA score < 11), the results showed a significant difference in the ratio between severe and both no impairment (p= 0.0009) and any impairment (p= 0.036). A ratio of maximum fiber tract density at the site of compression to fiber tract density at C-2 greater than 1.45 had 82% sensitivity and 70% specificity for identifying patients with moderate to severe impairment (ROC AUC= 0.8882, p= 0.0009). CONCLUSIONS These results support the use of DTI as a surrogate for determining spinal cord integrity in patients with cervical spondylosis. Probabilistic tractography provides spinal cord microstructural information that can help discern clinical status in cervical spondylosis patients with varying degrees of neurological impairment.

SUBMITTER: Ellingson BM

PROVIDER: S-EPMC5565223 | biostudies-other | 2015 Jun

REPOSITORIES: biostudies-other

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Project description:PurposeIn the present study we investigated a combination of diffusion tensor imaging (DTI) and magnetic resonance spectroscopic (MRS) biomarkers in order to predict neurological impairment in patients with cervical spondylosis.MethodsTwenty-seven patients with cervical spondylosis were evaluated. DTI and single voxel MRS were performed in the cervical cord. N-acetylaspartate (NAA) and choline (Cho) metabolite concentration ratios with respect to creatine were quantified, as well as the ratio of choline to NAA. The modified mJOA scale was used as a measure of neurologic deficit. Linear regression was performed between DTI and MRS parameters and mJOA scores. Significant predictors from linear regression were used in a multiple linear regression model in order to improve prediction of mJOA. Parameters that did not add value to model performance were removed, then an optimized multiparametric model was established to predict mJOA.ResultsSignificant correlations were observed between the Torg-Pavlov ratio and FA (R2 = 0.2021, P = 0.019); DTI fiber tract density and FA, MD, Cho/NAA (R2 = 0.3412, P = 0.0014; R2 = 0.2112, P = 0.016; and R2 = 0.2352, P = 0.010 respectively); along with FA and Cho/NAA (R2 = 0.1695, P = 0.033). DTI fiber tract density, MD and FA at the site of compression, along with Cho/NAA at C2, were significantly correlated with mJOA score (R2 = 0.05939, P < 0.0001; R2 = 0.4739, P < 0.0001; R2 = 0.7034, P < 0.0001; R2 = 0.4649, P < 0.0001). A combination biomarker consisting of DTI fiber tract density, MD, and Cho/NAA showed the best prediction of mJOA (R2 = 0.8274, P<0.0001), with post-hoc tests suggesting fiber tract density, MD, and Cho/NAA were all significant contributors to predicting mJOA (P = 0.00053, P = 0.00085, and P = 0.0019, respectively).ConclusionA linear combination of DTI and MRS measurements within the cervical spinal cord may be useful for accurately predicting neurological deficits in patients with cervical spondylosis. Additional studies may be necessary to validate these observations.

Project description:STUDY DESIGN:Case-control. OBJECTIVE:The aim of this study was to understand the role of high-resolution magnetic resonance (MR) in identifying regional cord volume loss in cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA:Preliminary studies suggest that compression of the ventral region of the cord may contribute disproportionately to CSM symptomology; however, tract-specific data are lacking in the CSM population. The current study is the first to use 3T MR imaging (MRI) images of CSM patients to determine specific volume loss at the level of detail of individual descending white matter tracts. METHODS:Twelve patients with CSM and 14 age-matched were enrolled prospectively and underwent 3-Tesla MRI of the cervical spine. Using the high-resolution images of the spinal cord, straightening and alignment with a template was performed and specific spinal cord tract volumes were measured using Spinal Cord Tool-box version 3.0.7. Modified Japanese orthopedic association (mJOA) and Nurick disability scores were collected in a prospective manner and were analyzed in relation to descending spinal tract volumes. RESULTS:Having CSM was predicted by anterior/posterior diameter, eccentricity of the cord [odds ratio (OR) 0.000000621, P?=?0.004], ventral reticulospinal tract volume (OR 1.167, P?=?0.063), lateral corticospinal tract volume (OR 1.034, P?=?0.046), rubrospinal tract volume (OR 1.072, P?=?0.011), and ventrolateral reticulospinal tract volume (OR 1.474, P?=?0.005) on single variable logistic regression. Single variable linear regression showed decreases in anterior/posterior spinal cord diameter (P?=?0.022), ventral reticulospinal tract volumes (P?=?0.007), and ventrolateral reticulospinal tract volumes (P?=?0.017) to significantly predict worsening mJOA scores. Similarly, decreases in ventral reticulospinal tract volumes significantly predicted increasing Nurick scores (P?=?0.039). CONCLUSION:High-resolution 3T MRI can detect tract-specific volume loss in descending spinal cord tracts in CSM patients. Anterior/posterior spinal cord diameter, ventral reticulospinal tract, ventrolateral reticulospinal tract, lateral corticospinal tract, and rubrospinal tract volume loss are associated with CSM symptoms. LEVEL OF EVIDENCE:2.

Project description:MethodsTwenty patients with CSM and 17 controls were recruited. Clinical scores of modified Japanese Orthopedic Association (mJOA) and Nurick were collected. MRI based compression grades such as cord distortion were assessed. Hand dysfunction was tested using a custom motorized apparatus. Subject's forearm was placed in a cast and positioned such that their metacarpophalangeal (MCP) joint was vertically aligned with the motor shaft. Surface electromyographic sensors were placed on flexor digitorum superficialis (FDS) and extensor digitorum communis muscles. Hyperreflexia was measured as the FDS muscle activation during reflex when the MCP joint was moved from flexion to extension at 300°/sec. Proprioception was quantified as the angle of detection in absence of visual or auditory cues (subjects were blindfolded and given noise-cancelling headphones). Strength was measured as the maximum isometric force at the MCP joint. 2-sample t-test (p<0.05) were performed to assess significant differences in reflexes, proprioception and strength among patients and controls (SPSS software version 24).ResultsPatients reported higher Nurick (1.90±1.0 vs 0±0, p<0.001) and lower mJOA scores (14.3±1.9 vs 18.0±0, p<0.001) as compared to controls. Similarly, patients with CSM had increased reflexes (peak FDS EMG) (0.073±0.096 vs. 0.014±0.010, p = 0.019). Patient proprioception was significantly worse; mean angle of detection was greater than twice as high in patients (9.6± 9.43°) compared to controls (4.0± 2.3°), p = 0.022. MRI based compression ratio (CR) was a significant predictor of hyperreflexia, CR<0.44 resulted in steep increase in reflex activity. Fifteen of the 20 patients who completed follow up testing at 6 months after surgery show substantial clinical improvement in reflexes and proprioceptive angle, while repeated testing in controls were unchanged.ConclusionIn conclusion, hyperreflexia and decline in proprioception are the main drivers of hand disability in patients with CSM. Of multiple scales, only a select few MRI scales (such as compression ratio) were predictive of increased reflexes. The study describes a pre-clinical testing apparatus to quantitatively and objectively assess primary presenting symptoms in CSM. This pilot apparatus has the potential to evaluate treatment efficacy through repeated testing. Objective testing of hand dysfunction can help inform the design of clinically feasible devices, guide MRI biomarker analysis, and improve our understanding of the progression of neurological injury in this patient population.

Project description:Cervical spondylotic myelopathy (CSM) is a degenerative condition of the spine that caused by static and dynamic compression of the spinal cord. However, the mechanisms of motor and somatosensory conduction, as well as pathophysiological changes at dynamic neck positions remain unclear. This study aims to investigate the interplay between neurophysiological and hemodynamic responses at dynamic neck positions in the CSM condition, and the pathological basis behind. We first demonstrated that CSM patients had more severe dynamic motor evoked potentials (DMEPs) deteriorations upon neck flexion than upon extension, while their dynamic somatosensory evoked potentials (DSSEPs) deteriorated to a similar degree upon extension and flexion. We therefore generated a CSM rat model which developed similar neurophysiological characteristics within a 4-week compression period. At 4 weeks-post-injury, these rats presented decreased spinal cord blood flow (SCBF) and oxygen saturation (SO2) at the compression site, especially upon cervical flexion. The dynamic change of DMEPs was significantly correlated with the change in SCBF from neutral to flexion, suggesting they were more sensitive to ischemia compared to DSSEPs. We further demonstrated significant vascular redistribution in the spinal cord parenchyma, caused by angiogenesis mainly concentrated in the anterior part of the compressed site. In addition, the comparative ratio of vascular densities at the anterior and posterior parts of the cord was significantly correlated with the perfusion decrease at neck flexion. This exploratory study revealed that the motor and somatosensory conductive functions of the cervical cord changed differently at dynamic neck positions in CSM conditions. Compared with somatosensory conduction, the motor conductive function of the cervical cord suffered more severe deteriorations upon cervical flexion, which could partly be attributed to its higher susceptibility to spinal cord ischemia. The uneven angiogenesis and vascular distribution in the spinal cord parenchyma might underlie the transient ischemia of the cord at flexion.

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Correlation between degree of subvoxel spinal cord compression measured with super-resolution tract density imaging and neurological impairment in cervical spondylotic myelopathy.

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