Study Design. Measurements of cervical and thoracolumbar human spinal cord (SC) geometry based on in vivo magnetic resonance imaging and investigation of morphological “invariants.”
Objective. The current work aims at providing morphological features of the complete in vivo human normal SC and at investigating possible “invariant” parameters that may serve as normative data for individualized study of SC injuries.
Summary of Background Data. Few in vivo magnetic resonance image–based studies have described human SC morphology at the cervical level, and similar description of the entire SC only relies on postmortem studies, which may be prone to atrophy biases. Moreover, large interindividual variations currently limit the use of morphological metrics as reference for clinical applications or as modeling inputs.
Methods. Absolute metrics of SC (transverse and anteroposterior diameters, width of anterior and posterior horns, cross-sectional SC area, and white matter percentage) were measured using semiautomatic segmentation of high resolution in vivo T2*-weighted transverse images acquired at 3 T, at each SC level, on healthy young (N = 15) and older (N = 8) volunteers. Robustness of measurements, effects of subject, age, or sex, as well as comparison with previously published postmortem data were investigated using statistical analyses (separate analysis of variance, Tukey-HSD, Bland-Altman). Normalized-to-C3 parameters were evaluated as invariants using a leave-one-out analysis. Spinal canal parameters were measured and occupation ratio border values were determined.
Results. Metrics of SC morphology showed large intra- and interindividual variations, up to 30% and 13%, respectively, on average. Sex had no influence except on posterior horn width (P < 0.01). Age-related differences were observed for anteroposterior diameter and white matter percentage (P < 0.05) and all postmortem metrics were significantly lower than in vivo values (P < 0.001). In vivo normalized SC area and diameters seemed to be invariants (R2 > 0.74, root-mean-square deviation < 10%). Finally, minimal and maximal occupation ratio were 0.2 and 0.6, respectively.
Conclusion. This study presented morphological characteristics of the complete in vivo human SC. Significant differences linked to age and postmortem state have been identified. Morphological “invariants” that could be used to calculate the normally expected morphology accurately, were also identified. These observations should benefit to biomechanical and SC pathology studies.
Level of Evidence: N/A
Absolute metrics of spinal cord and canal were measured on in vivo magnetic resonance images and ratios were as morphological invariants. Absolute measurements were age dependent whereas normalized spinal cord area, and normalized anteroposterior and transverse ratios presented low rootmean-square deviation and no statistical differences when comparing age and sex.
*Department of Mechanical Engineering, École de technologie supérieure, Montreal, Quebec, Canada
†Department of Medical Engineering, Research Center, Hôpital du Sacré-Cœur de Montréal, Montreal, Quebec, Canada
‡Laboratoire de Biomécanique Appliquée, Aix-Marseille Université, IFSTTAR-, Faculté de Médecine secteur Nord, Marseille, Cedex, France; and
§Centre de Résonance Magnétique Biologique et Médicale (CRMBM), Aix-Marseille Université, CNRS, Marseille, France.
Address correspondence and reprint requests to Virginie Callot, PhD, Centre de Résonance Magnétique Biologique et Médicale (CRMBM), UMR 7339, CNRS/Aix-Marseille Université, 27, Boulevard Jean Moulin, 13385 Marseille Cedex 05, France; E-mail: firstname.lastname@example.org
Acknowledgment date: February 26, 2013. First revision date: July 29, 2013. Second revision date: October 19, 2013. Acceptance date: October 28, 2013.
The manuscript submitted does not contain information about medical device(s)/drug(s).
CNRS, IFSTTAR, and ANR grant funds were received in support of this work.
Relevant financial activities outside the submitted work: consultancy, grants, patents, travel/accommodations/meeting expenses.