Morphometric dimensions of the caudal cervical vertebral column in clinically normal Doberman Pinschers, English Foxhounds and Doberman Pinschers with clinical signs of disk-associated cervical spondylomyelopathy

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Abstract

Client-owned, clinically normal Doberman Pinschers (n = 20), English Foxhounds (n = 17), and Doberman Pinschers with clinical signs of disk-associated cervical spondylomyelopathy (DA-CSM) (n = 17) were prospectively studied. All dogs underwent magnetic resonance imaging (MRI) of the cervical vertebral column. To evaluate vertebral canal stenosis, the canal occupying ratios of the spinal cord and cerebrospinal fluid (CSF)-column were calculated from C5 to C7. To evaluate the degree of spinal cord compression and the amount of canal compromise, the compression ratio, remaining spinal cord and CSF-column area, and vertebral canal and dorsoventral vertebral canal compromise ratios were calculated at the site of most severe compression.

For each canal occupying ratio, there was a significant higher value (implicating less space available for the spinal cord in the vertebral canal) at the level of C7 for clinically affected Doberman Pinschers compared with clinically normal English Foxhounds. The remaining spinal cord area was significantly smaller in dogs with clinically relevant spinal cord compression compared to dogs with clinically irrelevant spinal cord compression. Relative stenosis of the caudal cervical vertebral canal occurred more often in Doberman Pinschers with DA-CSM compared to English Foxhounds and a critical degree of spinal cord compression should be reached to result in clinical signs.

Introduction

In disk-associated cervical spondylomyelopathy (DA-CSM), caudal cervical spinal cord compression is typically caused by intervertebral disk protrusion, sometimes in combination with dorsal compression resulting from a hypertrophied ligamentum flavum (Van Gundy, 1988). The adult Doberman Pinscher is over-represented in dogs with DA-CSM (Van Gundy, 1988, Queen et al., 1998, Rusbridge et al., 1998, McKee et al., 1999, De Decker et al., 2009).

Magnetic resonance imaging (MRI) is increasingly used to diagnose DA-CSM (Levitski et al., 1999, da Costa et al., 2006a). A disadvantage of MRI is the potential for over-interpretation (Thomson et al., 1993). Several studies have demonstrated cervical MRI abnormalities in clinically normal dogs (da Costa et al., 2006b, De Decker et al., 2010). A recent study compared low-field MRI studies in dogs with and without clinical signs of DA-CSM and showed that low-field MRI of the cervical vertebral column can lead to incorrect assessments. Several clinically normal dogs demonstrated spinal cord compression, while some dogs with DA-CSM demonstrated only mild MRI abnormalities (De Decker et al., 2011).

It is currently unknown why some dogs tolerate cervical spinal cord compression while others develop clinical signs with only subtle MRI abnormalities. Furthermore, there is little information available about the degree of spinal cord compression or vertebral canal compromise necessary to result in clinical signs of cervical hyperesthesia or myelopathy. In the present study, we hypothesized that the relative dimensions of the caudal cervical vertebral column were different between Doberman Pinschers with clinical signs of DA-CSM, clinically normal Doberman Pinschers and clinically normal English Foxhounds.

Section snippets

Animals

The experiment was conducted in accordance with the guidelines of the Animal Care Committee of the University of Ghent (Approval numbers 2007/075, 2008/060, and 2008/091). Written owner consent was obtained prior to study enrolment.

Three groups of dogs were evaluated. The first group consisted of 17 client-owned Doberman Pinschers with clinical signs of DA-CSM. This group consisted of 6 males and 11 females (4.4–10 year old; median 7.0 years). Clinical signs varied from cervical hyperesthesia (n = 

Results

All clinically affected Doberman Pinschers demonstrated spinal cord compression. These compressions were considered to be clinically relevant. Additionally, 6/20 clinically normal Doberman Pinschers and 6/17 English Foxhounds demonstrated spinal cord compression which were considered clinically irrelevant. In the remaining clinically normal dogs (25/37), no spinal cord compression could be identified.

Eighteen of 20 clinically normal Doberman Pinschers and 9/17 English Foxhounds underwent a new

Discussion

Although the authors of this study have already described the morphological cervical MRI findings of clinically normal Doberman Pinschers, clinically normal English Foxhounds and dogs with DA-CSM, no results have yet been reported on the corresponding morphometric MRI parameters (De Decker et al., 2010, De Decker et al., 2011).

The major limitations of this study were that all measurements and neurological evaluations were performed by the same person and were not blinded to identity and

Conclusions

The results of this study suggest that relative stenosis of the caudal cervical vertebral canal occurs more often in Doberman Pinschers with clinical signs of DA-CSM compared to clinically normal English Foxhounds. Further, a certain amount of spinal cord compression should be reached before clinical signs occur. Considering the relative wide LOA for inter-observer agreement, caution should be taken with comparing measurements from different observers.

Conflict of interest statement

None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.

Acknowledgements

The first author and this study were supported by a PhD grant from the institute for the promotion of innovation by science and technology in Flanders (IWT).

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