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Reproducibility of tract-specific magnetization transfer and diffusion tensor imaging in the cervical spinal cord at 3 tesla.

ABSTRACT: Damage to specific white matter tracts within the spinal cord can often result in the particular neurological syndromes that characterize myelopathies such as traumatic spinal cord injury. Noninvasive visualization of these tracts with imaging techniques that are sensitive to microstructural integrity is an important clinical goal. Diffusion tensor imaging (DTI)- and magnetization transfer (MT)-derived quantities have shown promise in assessing tissue health in the central nervous system. In this paper, we demonstrate that DTI of the cervical spinal cord can reliably discriminate sensory (dorsal) and motor (lateral) columns. From data derived from nine healthy volunteers, two raters quantified column-specific parallel (lambda(||)) and perpendicular (lambda(perpendicular)) diffusivity, fractional anisotropy (FA), mean diffusivity (MD), and MT-weighted signal intensity relative to cerebrospinal fluid (MTCSF) over two time-points separated by more than 1 week. Cross-sectional means and standard deviations of these measures in the lateral and dorsal columns were as follows: lambda(||): 2.13 +/- 0.14 and 2.14 +/- 0.11 microm(2)/ms; lambda(perpendicular): 0.67 +/- 0.16 and 0.61 +/- 0.09 microm(2)/ms; MD: 1.15 +/- 0.15 and 1.12 +/- 0.08 microm(2)/ms; FA: 0.68 +/- 0.06 and 0.68 +/- 0.05; MTCSF: 0.52 +/- 0.05 and 0.50 +/- 0.05. We examined the variability and interrater and test-retest reliability for each metric. These column-specific MR measurements are expected to enhance understanding of the intimate structure-function relationship in the cervical spinal cord and may be useful for the assessment of disease progression.

SUBMITTER: Smith SA

PROVIDER: S-EPMC2830283 | biostudies-other | 2010 Feb

REPOSITORIES: biostudies-other

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Project description:Study designA case-control study.ObjectiveThe aim of this study was to understand the role of magnetization transfer ratio (MTR) in identifying patients with clinically significant myelopathy and disability.Summary of background dataMTR is a quantitative measure that correlates with myelin loss and neural tissue destruction in a variety of neurological diseases. However, the usefulness of MTR in patients with cervical spondylotic myelopathy (CSM) has not been examined.MethodsWe prospectively enrolled seven CSM patients and seven age-matched controls to undergo magnetic resonance imaging (MRI) of the cervical spine. Nurick, Neck Disability Index (NDI), and modified Japanese Orthopedic Association (mJOA) scores were collected for all patients. Clinical hyperreflexia was tested at the MCP joint, using a six-axis load cell. Reflex was simulated by quickly moving the joint from maximum flexion to maximum extension (300°/second). Anterior, lateral, and posterior cord MTR measurements were compared with clinical outcomes.ResultsCompared with controls, CSM patients had lower anterior cord MTR (38.29 vs. 29.97, Δ = -8.314, P = 0.0022), and equivalent posterior cord (P = 0.2896) and lateral cord (P = 0.3062) MTR. Higher Nurick scores were associated with lower anterior cord MTR (P = 0.0205), but not lateral cord (P = 0.5446) or posterior cord MTR (P = 0.1222). Lower mJOA was associated with lower anterior cord MTR (P = 0.0090), but not lateral cord (P = 0.4864) or posterior cord MTR (P = 0.4819). There was no association between NDI and MTR of the anterior (P = 0.4351), lateral (P = 0.7557), or posterior cord (P = 0.9171). There was a linear relationship between hyperreflexia and anterior cord MTR (slope = -117.3, R = 0.6598, P = 0.0379), but not lateral cord (P = 0.1906, R = 0.4511) or posterior cord (P = 0.2577, R = 0.3957) MTR.ConclusionAnterior cord MTR correlates with clinical outcomes as measured by mJOA index, Nurick score, and quantitative hyperreflexia, and could play a role in the preoperative assessment of CSM.Level of evidence2.

Project description:Spinal cord injuries (SCIs) are a leading cause of disability and can severely impact the quality of life. However, to date, the processes of spontaneous repair of damaged spinal cord remain incompletely understood, partly due to a lack of appropriate longitudinal tracking methods. Noninvasive, multiparametric magnetic resonance imaging (MRI) provides potential biomarkers for the comprehensive evaluation of spontaneous repair after SCI. In this study in rats, a clinically relevant contusion injury was introduced at the lumbar level that impairs both hindlimb motor and sensory functions. Quantitative MRI measurements were acquired at baseline and serially post-SCI for up to 2 wk. The progressions of injury and spontaneous recovery in both white and gray matter were tracked longitudinally using pool-size ratio (PSR) measurements derived from quantitative magnetization transfer (qMT) methods, measurements of water diffusion parameters using diffusion tensor imaging (DTI) and intrasegment functional connectivity derived from resting state functional MRI. Changes in these quantitative imaging measurements were correlated with behavioral readouts. We found (a) a progressive decrease in PSR values within 2 wk post-SCI, indicating a progressive demyelination at the center of the injury that was validated with histological staining, (b) PSR correlated closely with fractional anisotropy and transverse relaxation of free water, but did not show significant correlations with behavioral recovery, and (c) preliminary evidence that SCI induced a decrease in functional connectivity between dorsal horns below the injury site at 24 h. Findings from this study not only confirm the value of qMT and DTI methods for assessing the myelination state of injured spinal cord but indicate that they may also have further implications on whether therapies targeted towards remyelination may be appropriate. Additionally, a better understanding of changes after SCI provides valuable information to guide and assess interventions.

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Reproducibility of tract-specific magnetization transfer and diffusion tensor imaging in the cervical spinal cord at 3 tesla.

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