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

Spinal cord normalization in multiple sclerosis.

Author information

1
Department of Neurology, Johns Hopkins University.
2
Department of Physical Medicine and Rehabilitation, Johns Hopkins University.
3
Motion Analysis Laboratory, Kennedy Krieger Institute.
4
Department of Electrical and Computer Engineering, Johns Hopkins University.
5
Department of Computer Science, Johns Hopkins University.
6
Department of Biostatistics, Johns Hopkins University.
7
Department of Radiology and Radiological Science, Johns Hopkins University.
8
Translational Neuroradiology Unit, National Institute of Neurological Disorders and Stroke.

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

PMID:
24593281
PMCID:
PMC4156567
DOI:
10.1111/jon.12097
[Indexed for MEDLINE]
Free PMC Article

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