NeuroImage: Clinical (Jan 2019)

Rapid myelin water imaging for the assessment of cervical spinal cord myelin damage

  • Adam V. Dvorak,
  • Emil Ljungberg,
  • Irene M. Vavasour,
  • Hanwen Liu,
  • Poljanka Johnson,
  • Alexander Rauscher,
  • John L.K. Kramer,
  • Roger Tam,
  • David K.B. Li,
  • Cornelia Laule,
  • Laura Barlow,
  • Hannah Briemberg,
  • Alex L. MacKay,
  • Anthony Traboulsee,
  • Piotr Kozlowski,
  • Neil Cashman,
  • Shannon H. Kolind

Journal volume & issue
Vol. 23

Abstract

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Background: Rapid myelin water imaging (MWI) using a combined gradient and spin echo (GRASE) sequence can produce myelin specific metrics for the human brain. Spinal cord MWI could be similarly useful, but technical challenges have hindered routine application. GRASE rapid MWI was recently successfully implemented for imaging of healthy cervical spinal cord and may complement other advanced imaging methods, such as diffusion tensor imaging (DTI) and quantitative T1 (qT1). Objective: To demonstrate the feasibility of cervical cord GRASE rapid MWI in multiple sclerosis (MS), primary lateral sclerosis (PLS) and neuromyelitis optica spectrum disorder (NMO), with comparison to DTI and qT1 metrics. Methods: GRASE MWI, DTI and qT1 data were acquired in 2 PLS, 1 relapsing-remitting MS (RRMS), 1 primary-progressive MS (PPMS) and 2 NMO subjects, as well as 6 age (±3 yrs) and sex matched healthy controls (HC). Internal cord structure guided template registrations, used for region of interest (ROI) analysis. Z score maps were calculated for the difference between disease subject and mean HC metric values. Results: PLS subjects had low myelin water fraction (MWF) in the lateral funiculi compared to HC. RRMS subject MWF was heterogeneous within the cord. The PPMS subject showed no trends in ROI results but had a region of low MWF Z score corresponding to a focal lesion. The NMO subject with a longitudinally extensive transverse myelitis lesion had low values for whole cord mean MWF of 12.8% compared to 24.3% (standard deviation 2.2%) for HC. The NMO subject without lesions also had low MWF compared to HC. DTI and qT1 metrics showed similar trends, corroborating the MWF results and providing complementary information. Conclusion: GRASE is sufficiently sensitive to detect decreased myelin within MS spinal cord plaques, NMO lesions, and PLS diffuse spinal cord injury. Decreased MWF in PLS is consistent with demyelination secondary to motor neuron degeneration. GRASE MWI is a feasible method for rapid assessment of myelin content in the cervical spinal cord and provides complementary information to that of DTI and qT1 measures. Keywords: Mri, Myelin water imaging, Diffusion tensor imaging, Quantitative T1, Spinal cord