Spontaneous acute and chronic spinal cord injuries in paraplegic dogs: a comparative study of in vivo diffusion tensor imaging.

STUDY DESIGN: Prospective observational-analytical study.

OBJECTIVES: Description of diffusion tensor imaging (DTI) metrics obtained from the spinal cord (SC) of dogs with severe acute or chronic spontaneous, non-experimentally induced spinal cord injury (SCI) and correlation of DTI values with lesion extent of SCI measured in T2-weighted (T2W) magnetic resonance imaging sequences.

SETTING: Hannover, Germany.

METHODS: Forty-seven paraplegic dogs, 32 with acute and 15 with chronic SCI, and 6 disease controls were included. T2W and DTI sequences of the thoracolumbar spinal cord were performed. Values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were obtained from the epicentre of the lesion and one SC segment cranially and caudally and compared between groups. Pearson's correlation coefficient was calculated between DTI and T2W metrics.

RESULTS: During acute SCI, FA values were increased (P=0.0065) and ADC values were decreased (P=0.0099) at epicentres compared to disease controls. FA values obtained from dogs with chronic SCI were lower (P<0.0001 epicentres and caudally; P=0.0002 cranially) and ADC showed no differences compared to disease control values. Dogs with chronic SCI revealed lower FA and higher ADC compared to dogs with acute SCI (P<0.0001 for both values at all localisations). FA values from epicentre and cranially to the lesion during chronic SCI correlated with extent of lesion (r=0.5517; P=0.0052 epicentres and r=0.6810; P=0.0408 cranially).

CONCLUSION: Using DTI, differences between acute and chronic stages of spontaneous canine SCI were detected and correlations between T2W and DTI sequences were found in chronic SCI, supporting canine SCI as a useful large animal model.