Magnetic resonance tractography of the cervical spine: Toward routine clinical use

Abstract

Spinal cord injury and non-traumatic myelopathies are major causes of lifelong disability, yet conventional magnetic resonance imaging (MRI) can underestimate microstructural damage. Diffusion tensor imaging (DTI) and tractography map white-matter integrity by measuring fractional anisotropy (FA) and mean diffusivity (MD), but their adoption in spine imaging has been limited by long scan times and complex post-processing. Supsupin et al report a two-minute cervical DTI sequence integrated into routine MRI and applied to four representative pathologies – spinal cord contusion, metastatic compression, degenerative myelopathy, and multiple sclerosis – compared with five controls. Each lesion showed distinctive tractographic and quantitative patterns: For example, reduced FA with preserved MD in contusion and combined FA decrease and MD elevation in metastatic compression. These findings highlight the potential of tractography to improve diagnosis, guide surgical planning, and monitor treatment, while maintaining clinical feasibility. Remaining challenges include limited angular resolution, motion artifacts, and the need for multicenter validation and advanced reconstruction methods. This manuscript places the study in the context of current spinal diffusion imaging and outlines future directions toward routine, precision care.

Key Words: Magnetic resonance imaging; Tractography; Cervical; Spine; Diffusion tensor imaging

Core Tip: A rapid two-minute diffusion tensor imaging sequence enables cervical spinal cord tractography during routine magnetic resonance imaging (MRI). Supsupin et al demonstrate that distinct fractional anisotropy and mean diffusivity patterns reveal microstructural injury in contusion, metastasis, degenerative myelopathy, and multiple sclerosis – lesions that may appear less conspicuous on conventional MRI. Their work shows how tractography can support diagnosis, surgical planning, and longitudinal follow-up.

TO THE EDITOR

Spinal cord disorders including trauma, degenerative myelopathy, metastatic disease, and demyelinating disorders are major causes of lifelong disability and reduced quality of life. Globally, hundreds of thousands of people sustain spinal cord injury each year, and many more live with chronic compressive or inflammatory conditions. Early detection of microstructural cord damage is critical for prognosis, surgical planning, and monitoring therapeutic response[1]. Conventional magnetic resonance imaging (MRI), while indispensable for depicting gross cord morphology and signal changes, often fails to reveal subtle axonal injury or the precise extent of fiber disruption.

Diffusion tensor imaging (DTI) and tractography, which reconstruct the three-dimensional organization of white matter fibers, provide a window into these otherwise invisible changes. By measuring the directionality of water diffusion, DTI quantifies fractional anisotropy (FA) and mean diffusivity (MD), surrogate markers of axonal integrity and extracellular edema. Tractography then integrates these data to render a virtual map of cord tracts, offering the possibility of more accurate diagnosis and individualized management[2-4]. Despite this promise, spinal applications of tractography have lagged behind cranial uses because of long acquisition times, motion artifacts, and the need for specialized post-processing.

STUDY HIGHLIGHTS

In this issue of World Journal of Radiology, Supsupin et al[5] demonstrate that these barriers can be substantially lowered. They incorporated a 2-minute cervical spine DTI sequence into routine MRI and used deterministic tractography with automated topology-informed pruning to evaluate four representative pathologies – cord contusion, metastatic compression, degenerative myelopathy, and multiple sclerosis – against five healthy controls.

Distinct tractographic signatures emerged. In the cord contusion case, FA was reduced at the lesion with preserved MD, consistent with axonal disorganization without widespread necrosis or edema. Metastatic compression produced both decreased FA and elevated MD, reflecting tract disruption and tissue infiltration. Degenerative myelopathy demonstrated visual tract interruption despite relatively preserved FA, illustrating how selective fiber loss or partial-volume effects can mask scalar abnormalities[6]. Finally, demyelinating disease revealed moderate FA reduction with only mild MD elevation, a pattern compatible with localized myelin loss.

These quantitative and qualitative findings provide a more nuanced picture than conventional MRI alone and illustrate how tractography can inform surgical or medical decision-making when conventional images underestimate the severity of fiber injury[7].

CLINICAL SIGNIFICANCE

The clinical implications are substantial. First, the authors’ ultra-short acquisition, about two minutes added to the MRI exam, addresses one of the main impediments to routine spinal tractography[5]. Second, the combination of rapid acquisition and straightforward deterministic reconstruction supports integration into standard clinical workflows, including preoperative planning for tumor resection or decompressive surgery, and serial follow-up in demyelinating disease. Third, FA and MD measurements derived from the lesion core and adjacent segments may help predict neurological outcomes and guide rehabilitation, paralleling similar applications of brain tractography in stroke and trauma[4,8].

These strengths align with the growing emphasis on precision medicine. Reliable early identification of microstructural injury may allow targeted interventions to prevent secondary degeneration, optimize timing of surgery, and monitor therapeutic efficacy.

TECHNICAL CONTEXT AND CHALLENGES

Spinal tractography presents unique technical hurdles. The cervical cord’s small cross-section, surrounding cerebrospinal fluid, and frequent patient motion create geometric distortions and lower signal-to-noise ratios. Supsupin et al[5] used a six-direction acquisition, a pragmatic choice for minimizing scan time but one that limits angular resolution and sensitivity to complex fiber crossings[9]. Higher-direction acquisitions – typically at least 17 directions – yield more accurate tractography but at the cost of longer imaging times and greater motion sensitivity.

Another challenge is the fundamental limitation of the DTI model, which assumes a single dominant fiber orientation per voxel. This can obscure crossing, merging, or branching fibers. Advanced reconstruction methods such as generalized q-sampling imaging can resolve multiple orientations and may improve anatomic fidelity, though at the price of longer acquisitions and more complex post-processing[10]. Distortion-correction strategies, including reverse phase-encoding and cardiac gating, could further enhance data quality[8].

BROADER PERSPECTIVE

The work by Supsupin et al[5] dovetails with a growing literature that seeks to translate tractography from research to everyday clinical care. Several groups have shown that FA correlates with neurological impairment and outcome in cervical myelopathy[6] and that diffusion changes can signal disease activity in demyelinating conditions[4]. In neurosurgical planning, tractography has already improved the safety of tumor resection and deep brain stimulation[8]. By applying similar principles to the spinal cord in a rapid, clinically feasible manner, the current study advances the field toward true bedside applicability.

Looking ahead, multi-institutional studies with larger, pathologically diverse cohorts will be essential to validate diagnostic accuracy and prognostic value. Integration with surgical navigation systems, machine-learning-based segmentation, and quantitative outcome measures could further enhance clinical impact. Importantly, reproducibility across different scanners and institutions must be established if the method is to inform treatment guidelines and reimbursement decisions.

CONCLUSION

By showing that robust cervical spinal cord tractography can be performed with minimal additional scan time, Supsupin et al[5] provide a practical framework for incorporating diffusion imaging into daily radiological practice. Their rapid DTI protocol delivers actionable insights into microstructural integrity across a spectrum of diseases, bringing us closer to an era where spinal tractography complements conventional MRI as a standard component of precision spinal care.