MR-histological Correlations of Wallerian Degeneration in Spinal Cord Injury

Cho, Kyoung Suok; Bunge, Richard P; Choi, Chag Rak

Abstract

The purposes of this study were to describe the magnetic resonance(MR) manifestations of wallerian degeneration occurring above and below a spinal cord injury site, to determine the post-injury time interval when the wallerian degeneration becomes evident in MR images, and to correlate the MR findings with post mortem histopathology. Twenty-three postmortem spinal cords, all from patients with cervical(14), thoracic(5), and lumbar(4) cord injuries, were studied with axial TI-and T2-weighted spin-echo MR imaging. Injury to death intervals varied from 8 days to 22 years. We examined these specimen for abnormal cord contour and alteration of signal above and below the injury site. Histological studies of these cords with axon, myelin, and connective tissue stains were performed at levels equivalent to the MR sections. Studies using plastic embedded sections and antibodies to Glial Fibrillary Acetic Protein(GFAP) were also performed on some of the above cords. Pathological-imaging correlations were made. MR images of the cord specimen showed increased signal intensity in the dorsal columns above the injury level as well as in the lateral corticospinal tracts below the injury level in all cases in which cord injury had occurred seven or more weeks premortem. In one case where cord injury had occurred eight days prior to death the MR showed no signal abnormalities, histological analysis showed evidence of early wallerian degeneration in the dorsal columns above the lesion but no change was detected in the lateral columns below the lesion. After 12 days, early stage wallerian degeneration was detected by histological examination in both the lateral columns below the lesion and in the dorsal columns above the lesion. Wallerian degeneration in spinal cords, as demonstrated by histological examination, was identified on MR as areas of increased T2 weighted signal intensity site in the dorsal column above the injury site and in the corticospinal tracts below the injury site in all specimen in which the injury-to-death interval was greater than 7 weeks. The ability to recognize wallerian degeneration on MR allows a more comprehensive analysis of the injury, explains abnormal MR signals at sites that are remote from the epicenter of injury, and may be helpful in the assessing of results of therapeutic interventions.