Diffusion magnetic resonance imaging reveals tract‐specific microstructural correlates of electrophysiological impairments in non‐myelopathic and myelopathic spinal cord compression

Background and purpose: Non- myelopathic degenerative cervical spinal cord compres-sion (NMDC) frequently occurs throughout aging and may progress to potentially irre-versible degenerative cervical myelopathy (DCM). Whereas standard clinical magnetic resonance imaging (MRI) and electrophysiological measures assess compression sever-ity and neurological dysfunction, respectively, underlying microstructural deficits still have to be established in NMDC and DCM patients. The study aims to establish tract- specific diffusion MRI markers of electrophysiological deficits to predict the progression of asymptomatic NMDC to symptomatic DCM.

Methods: High-resolution 3 T diffusion MRI was acquired for 103 NMDC and 21 DCM patients compared to 60 healthy controls to reveal diffusion alterations and relation-ships between tract-specific diffusion metrics and corresponding electrophysiological measures and compression severity. Relationship between the degree of DCM disability, assessed by the modified Japanese Orthopaedic Association scale, and tract-specific mi-crostructural changes in DCM patients was also explored.

Results: The study identified diffusion-derived abnormalities in the gray matter, dor-sal and lateral tracts congruent with trans-synaptic degeneration and demyelination in chronic degenerative spinal cord compression with more profound alterations in DCM than NMDC. Diffusion metrics were affected in the C3-6 area as well as above the com-pression level at C3 with more profound rostral deficits in DCM than NMDC. Alterations in lateral motor and dorsal sensory tracts correlated with motor and sensory evoked po-tentials, respectively, whereas electromyography outcomes corresponded with gray mat-ter microstructure. DCM disability corresponded with microstructure alteration in lateral columns.

Conclusions: Outcomes imply the necessity of high- resolution tract-specific diffusion MRI for monitoring degenerative spinal pathology in longitudinal studies.