Compression analysis of the gray and white matter of the spinal cord

Nishida, Norihiro; Jiang, Fei; Ohgi, Junji; Tanaka, Akihiro; Imajo, Yasuaki; Suzuki, Hitomi; Funaba, Masahiro; Sakai, Takashi; Sakuramoto, Itsuo; Chen, Xian

doi:10.4103/1673-5374.272604

Cited by 7 publications

(2 citation statements)

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“…Concentric, tightly compacted wraps form a robust lamina that acts as a capacitor, insulating axon segments and facilitating saltatory conduction at axonal nodes 3 . When CNS fibers are mildly compressed (eg, during injury), the bilipid myelin membranes may delaminate and degenerate, dysregulating conduction velocity along axons 4–6 . Specifically, in instances of mild injury, the myelin structure is altered and fiber conduction velocities are dysregulated, giving rise to a variety of neurological maladies 7,8 .…”

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confidence: 99%

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Quantification of Myelinated Nerve Fraction and Degeneration in Spinal Cord Neuropil by SHIFT MRI

Wolfe

Hoffman

Hogan

et al. 2020

Magnetic Resonance Imaging

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Background Neurodegeneration is a complex cellular process linked to prompt changes in myelin integrity and gradual neuron loss. Current imaging techniques offer estimations of myelin volumes in lesions/remyelinated areas but are limited to detect subtle injury. Purpose To investigate whether measurements detected by a signal hierarchically isolated as a function of time‐to‐echo (SHIFT) MRI technique can determine changes in myelin integrity and fiber axolemma. Study Type Prospective animal model. Animal Model Surgically demyelinated spinal cord (SC) injury model in rodents (n = 6). Field Strength/Sequence Gradient‐echo spin‐echo at 3T. Assessment Multicompartment T2 relaxations were computed by SHIFT MRI in 75‐microns‐resolution images of the SC injury penumbra region 2 weeks post‐trauma. G‐ratio and axolemma delamination were assessed by transmission electron microscopy (TEM) in intact and injured samples. SC myelinated nerve fraction was computed by SHIFT MRI prospectively and assessed histologically. Statistical Tests Relations between SHIFT‐isolated T2‐components and TEM measurements were studied using linear regression and t‐tests. Pearson's correlation and significance were computed to determine the SHIFT's sensitivity to detect myelinated fibers ratio in gray matter. Regularized least‐squares‐based ranking analysis was employed to determine SHIFT MRI's ability to discern intact and injured myelinated nerves. Results Biexponential signals isolated by SHIFT MRI for intact vs. lesion penumbra exhibited changes in T2, shifting from intermediate components (25 ± 2 msec) to long (43 ± 11 msec) in white matter, and similarly in gray matter regions‐of‐interest (31 ± 2 to 46 ± 16 msec). These changes correlated highly with TEM g‐ratio and axon delamination measurements (P < 0.05). Changes in short T2 components were observed but not statistically significant (8.5 ± 0.5 to 7 ± 3 msec, P = 0.445, and 4.0 ± 0.9 to 7 ± 3 msec, P = 0.075, respectively). SHIFT MRI's ability to detect myelinated fibers within gray matter was confirmed (P < 0.001). Data Conclusion Changes detected by SHIFT MRI are associated with abnormal intermembrane spaces formed upon mild injury, directly correlated with early neuro integrity loss. Level of Evidence 1 Technical Efficacy Stage 2

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“…Assessment of myelin fractions in white matter is remarkably relevant for evaluating CNS responses to proposed therapeutics in these cases. Nonetheless, myelination density changes alone may not be as prominent in mild white matter injury 5–7,26 …”

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confidence: 99%