Spinal cord normalization in multiple sclerosis

J Neuroimaging. Nov-Dec 2014;24(6):577-584. doi: 10.1111/jon.12097. Epub 2014 Mar 5.

Abstract

Background: Spinal cord (SC) pathology is common in multiple sclerosis (MS), and measures of SC-atrophy are increasingly utilized. Normalization reduces biological variation of structural measurements unrelated to disease, but optimal parameters for SC volume (SCV)-normalization remain unclear. Using a variety of normalization factors and clinical measures, we assessed the effect of SCV normalization on detecting group differences and clarifying clinical-radiological correlations in MS.

Methods: 3T cervical SC-MRI was performed in 133 MS cases and 11 healthy controls (HC). Clinical assessment included expanded disability status scale (EDSS), MS functional composite (MSFC), quantitative hip-flexion strength ("strength"), and vibration sensation threshold ("vibration"). SCV between C3 and C4 was measured and normalized individually by subject height, SC-length, and intracranial volume (ICV).

Results: There were group differences in raw-SCV and after normalization by height and length (MS vs. HC; progressive vs. relapsing MS-subtypes, P < .05). There were correlations between clinical measures and raw-SCV (EDSS:r = -.20; MSFC:r = .16; strength:r = .35; vibration:r = -.19). Correlations consistently strengthened with normalization by length (EDSS:r = -.43; MSFC:r = .33; strength:r = .38; vibration:r = -.40), and height (EDSS:r = -.26; MSFC:r = .28; strength:r = .22; vibration:r = -.29), but diminished with normalization by ICV (EDSS:r = -.23; MSFC:r = -.10; strength:r = .23; vibration:r = -.35). In relapsing MS, normalization by length allowed statistical detection of correlations that were not apparent with raw-SCV.

Conclusions: SCV-normalization by length improves the ability to detect group differences, strengthens clinical-radiological correlations, and is particularly relevant in settings of subtle disease-related SC-atrophy in MS. SCV-normalization by length may enhance the clinical utility of measures of SC-atrophy.

Keywords: MRI; Multiple sclerosis; atrophy; normalization; spinal cord.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Female
  • Humans
  • Image Interpretation, Computer-Assisted / standards*
  • Magnetic Resonance Imaging / standards*
  • Male
  • Middle Aged
  • Multiple Sclerosis / pathology*
  • Reference Values
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Spinal Cord / pathology*