Elsevier

NeuroImage

Volume 84, 1 January 2014, Pages 1082-1093
NeuroImage

Review
The current state-of-the-art of spinal cord imaging: Applications

https://doi.org/10.1016/j.neuroimage.2013.07.014Get rights and content

Highlights

  • Clinical challenges encountered in imaging of the spinal cord are presented.

  • Description of functional MRI of the spinal cord applications

  • Description of diffusion tensor imaging of the spinal cord applications

  • Specific findings in spinal cord pathologies

Abstract

A first-ever spinal cord imaging meeting was sponsored by the International Spinal Research Trust and the Wings for Life Foundation with the aim of identifying the current state-of-the-art of spinal cord imaging, the current greatest challenges, and greatest needs for future development. This meeting was attended by a small group of invited experts spanning all aspects of spinal cord imaging from basic research to clinical practice. The greatest current challenges for spinal cord imaging were identified as arising from the imaging environment itself; difficult imaging environment created by the bone surrounding the spinal canal, physiological motion of the cord and adjacent tissues, and small crosssectional dimensions of the spinal cord, exacerbated by metallic implants often present in injured patients. Challenges were also identified as a result of a lack of “critical mass” of researchers taking on the development of spinal cord imaging, affecting both the rate of progress in the field, and the demand for equipment and software to manufacturers to produce the necessary tools. Here we define the current state-of-the-art of spinal cord imaging, discuss the underlying theory and challenges, and present the evidence for the current and potential power of these methods. In two review papers (part I and part II), we propose that the challenges can be overcome with advances in methods, improving availability and effectiveness of methods, and linking existing researchers to create the necessary scientific and clinical network to advance the rate of progress and impact of the research.

Introduction

Our ability to research and understand human spinal cord function, its role in pain processing, the effects of traumatic injury or diseases such as multiple-sclerosis, and our understanding of pain processing, is all significantly hampered by the limited accessibility of the spinal cord. In the part I of our two part series we have described the current state-of-the-art of spinal cord imaging, the current greatest challenges, and the greatest needs for future development in order to support non-invasive human spinal cord research (Stroman et al., 2014). The general assumption is that providing increased sensitivity and specificity of spinal cord imaging in the context of well-defined clinical readouts will be instrumental to improve novel approaches in the diagnostic and treatment of spinal cord diseases. The objectives of this paper are to:

  • 1)

    describe the current state-of-the-art and capabilities of human spinal cord imaging applications;

  • 2)

    identify the greatest current needs, from a clinical point of view, that will drive forward future development.

In order to achieve these objectives we provide a general overview of two key techniques employed in clinical research, functional Magnetic Resonance Imaging (fMRI) and Diffusion Tensor Imaging (DTI), and then focus on specific applications of spinal cord imaging on four areas: investigations of cervical spondylotic myelopathy (CSM), spinal cord injury (SCI), pain and multiple-sclerosis (MS). Wherever applicable, reference to quantitative imaging methods other than fMRI and DTI, such as magnetic resonance spectroscopy (MRS) and magnetization transfer (MT) imaging, will also be mentioned. Issues related to spatial resolution, registration of subsequently acquired volumes, partial volume effects with the cerebrospinal fluid (CSF), as well as the lack of a standard common template and the effects of physiological noise are still limiting the adoption of many techniques into the clinical setting, confounding quantitative MRI of the spinal cord to research studies. The overall goal of this work is therefore to foster the development of novel and sensitive means of characterizing neural function and cellular structure in clinical populations that can supplement or surpass current methods for patient assessment, serve as clinical trial endpoints, and be used for monitoring of disease progression and efficacy of therapies.

Section snippets

fMRI in the human spinal cord: Applications

A growing number of studies (summarized in Table 1) have been carried out to investigate spinal cord function in response to various sensory stimuli and motor tasks and to characterize the effects of traumatic injury and pathology.

Determining the sensitivity and reliability of spinal cord fMRI is a challenging task in that there is no “gold-standard” method that can be used to verify the results obtained in humans (Stroman et al., 2014). Even studies with animal models (Lawrence et al., 2004,

Spondylotic myelopathy

Spinal cord compression can be caused by various pathological processes such as neoplasms, degenerative changes, inflammatory processes and trauma. Degenerative spine disease is the most common and may have enormous effects on the patients' quality of life (Kara et al., 2011). Progressive compression of the spinal cord due to narrowing of the spinal canal is the main pathophysiology underlying the non-traumatic myelopathy. Early diagnosis and appropriately chosen treatment may prevent further

Spinal cord injury

Improving our ability to assess tissue viability and detect residual neuronal function in the spinal cord, in order to identify and distinguish morphological and functional changes, is key to advancing our capacity for clinical prognosis and management of spinal cord injury patients. A recently published prospective longitudinal study in chronic SCI investigated the motor system, including cervical spinal cord, cranial corticospinal tract (CST) and motor cortex, in particular correlating

Pain

The spinal cord (and brainstem) is the first point in the central nervous system that processes nociceptive signals arriving from the body, and which ultimately may produce a sensation of pain. Functional imaging of the spinal cord aims to record this activity and can help to better understand how these signals are processed and whether altered spinal cord function underlies chronic or neuropathic pain states in humans. Nociceptors, free nerve endings located in skin, muscles and viscera,

Multiple sclerosis

Multiple sclerosis (MS) is the disease that has benefitted mostly from advanced quantitative spinal cord imaging techniques, spanning from cord atrophy measurements, fMRI, DTI and also magnetization transfer ratio (MTR), myelin imaging and proton MRS, as described in this section. Fig. 5 is showing an example of some of these techniques in a patient with MS at cervical level.

Cord lesions in MS are more frequently observed in the cervical than in other regions, are usually peripheral, limited to

Concluding statements

Significant advances in spinal cord imaging methods have been realized in the past decade. The great potential of such methods to support research into basic neuroscience and novel treatment strategies, as well as to improve clinical diagnoses, and the monitoring of treatment and rehabilitation outcomes have been well-demonstrated. The realization of methods to provide the desired research and clinical tools still requires technological development. In part I we reported the greatest technical

Acknowledgments

This work is the result of the efforts of the International Spinal Research Trust and the Wings for Life Spinal Cord Research Foundation to bring together researchers with a common goal of developing non-invasive imaging tools for basic and clinical spinal cord research and to support advances in treatment and rehabilitation. The goal is to speed advances and make these imaging tools more widely available by promoting collaboration between researchers and by identifying the most important

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