Syringomyelia MRI Screening Protocol For Cavalier King Charles Spaniels

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Syringomyelia (SM) MRI Screening Protocol

CavalierHealth.org Copyright © 2004 Blenheim Company Dr. Clare Rusbridge, BVMS DipECVN MRCVS, of the Stone Lion Veterinary Centre in Wimbledon, UK, has published the following protocol in October 2006, for veterinarians who perform magnetic resonance imaging (MRI) scanning to diagnose dogs suspected of having syringomyelia (SM) or Chiari-like malformation (CM), which is also known as occipital hypoplasia (OH) or caudal occipital malformation syndrome (COMS). It includes her guidelines for full studies and for minimum (low cost) imaging.

Basic MRI Screening Protocol for SM -- COMS -- OH

by Clare Rusbridge, BVMS DipECVN MRCVS PhD.

Positioning:

I take care to get the dog as "straight" as possible -- most useful to use the dorsal localiser (i.e. coronal in human terminology). I position the dog in sternal recumbency (i.e. prone, in human terminology) -- if in lateral, then must have head wedged into full extension.

Area covered: Copyright © 2007 Long Island Veterinary Specialists

I image from ~ level of the thalamus / corpus callosum to as far caudal as possible.

For minimum (i.e. low cost) imaging, three (3) sequences are done. If paying full price for a scan, I would expect a full study of the areas covered.

Minimum scan:

1) T1 sagittal

2) Turbo spin echo or T2W sagittal

3) Transverse (i.e. equivalent of axial for human) T1W or T2W, ensuring that one of the slices goes though the spinal Copyright © 2007 Long Island Veterinary Specialists cord above the C2/C3 disc space. The choice of T2W or T1W depends on the tesla of the Machine. For low tesla machines, like our in house scanner which is 0.2T machine, a TW1 3d image centering on the C2/C3 disc gives me the clearest information. For the 1.5T machines we also have access to, I prefer T2W transverses (axials) that are about 7-9mm apart, giving about 16 slices through the entire region, including a slice through the tympanic bullae, the cranial cervical junction, and the C2/C3 disc.

Generally, TW1 is better on low tesla machines and T2W on high tesla, but on an individual machine it can be worth trying both, at least initially. If unsure, both are taken.

Additional images:

1) If the dog has severe scoliosis, so that mid-line sagittal images are unclear, I obtain a dorsal (coronal image).

2) If the dog has epilepsy, I obtain a brain study.

3) If another cause of cervical pain is identified (e.g. disc disease), then appropriate images are taken.

Kind regards, Clare Rusbridge

Stone Lion Veterinary Centre, 41 High Street, Wimbledon, London, SW19 5AU. Telephone 0208 946 4228, e-mail neuro.vet@btinternet.com

Veterinary Resources

Neurological signs and results of magnetic resonance imaging in 40 cavalier King Charles spaniels with Chiari type 1-like malformations. Lu D, Lamb CR, Pfeiffer DU, Targett MP. Vet Rec. Aug 2003;153(9):260-3.

The Use of Ultrasonography to Diagnose “Caudal Occipital Malformation Syndrome” in Dogs – a Prospective Study in 12 Dogs. B Levitin, JJ McDonnell, D Faissler, AS Tidwell. J Vet Intern Med; May/June 2005;19(3) (ACVIM 23rd Ann. Vet. Med. Forum Abstract Program: Abstract 209).

Brain Stem Auditory Evoked Response (BAER) Testing in Cavalier King Charles Spaniels with Caudal Occipital Malformation Syndrome. CW Dewey, KS Bailey, G Barone, J Stefanacci. J Vet Intern Med; May/June 2006;20(3) (ACVIM 24th Ann. Vet. Med. Forum Abstract Program: Abstract 270).

Syringomyelia in cavalier King Charles spaniels: the relationship between syrinx dimensions and pain. C Rusbridge, H Carruthers, M-P Dubé, M Holmes, N D Jeffery. J Small Anim. Pract. 2007 Aug;48(8):432-6. Quote: "Objectives: This study was designed to test the hypothesis that pain associated with syringomyelia in dogs is dependent upon size and involvement of the dorsal part of the spinal cord. Methods: Masked observers determined syrinx dimensions and precise location within the spinal cord on magnetic resonance images of 55 cavalier King Charles spaniels with syringomyelia. After removal of masking, syrinx size and location were compared between the cohorts of dogs that exhibited pain with those that did not. Results: Maximum syrinx width was the strongest predictor of pain, scratching behaviour and scoliosis in dogs with syringomyelia. Both pain and syrinx size were positively correlated with syrinxes located in the dorsal half of the spinal cord. Clinical Significance: Large syrinxes associated with damage to the dorsal part of the spinal cord are associated with persistent pain suggesting that the pain behaviour expressed by this group of patients is likely to be 'neuropathic pain', resulting from disordered neural processing in the damaged dorsal horn. As such it is likely that conventional analgesic medication may be ineffective."

Magnetic resonance imaging - unravelling the mystery. J. Fraser McConnell. J Small Anim. Pract. 2007 Aug;48(8): 421-422. Quote: "With evidence based medicine in vogue the study by Claire Rusbridge and colleagues (Rusbridge and others 2007) is to be congratulated and is of particular value as it contains a cohort of dogs with no clinical signs. Obtaining MR images of neurologically normal animals can be difficult as it is often not possible to justify anaesthesia in such animals. The use of MRI screening prior to breeding gives valuable information from a group of clinically normal animals. ... Reliance on statistical analyses alone can be misleading when it comes to determining the significance of MRI changes for an individual animal. While the diagnosis of syringohydromyelia in cavalier King Charles spaniels is straightforward with MRI, the problem is one of interpreting what the changes will mean for an individual. It has long been recognised that there is a poor correlation between severity of MRI abnormalities and whether the dog will show clinical signs with syringomyelia. This was shown by Lu and others (2003) who found no correlation between the severity of the syrinx and presence of neurological signs relating to the spine; some dogs with marked syringomyelia having no spinal signs (Lu and others 2003). The study by Rusbridge and colleagues in this issue reports different results and found, not surprisingly, that the larger the syrinx the more likely the individual will show clinical signs. While the study suggests that assessing syrinx size based on transverse plane images may be a more useful method than length of syrinx this does not give all the answers to the problem of interpretation. The data shows that while there is a good correlation between size of syrinx and pain there is an almost complete overlap of the range of syrinx size between the two groups. The significance of this is that it is still not possible to state with certainty, based on the MRI findings, whether a dog will develop clinical signs. It is likely that functional imaging such as CSF flow studies will be required to unpick the complexity of syringomyelia in cavalier King Charles spaniels. Similar findings have been reported in other areas of neuroimaging such as degenerative lumbosacral stenosis and intervertebral disk disease (Penning and others 2006, Mayhew and others 2002, Suwankong and others 2006) It is clear that with all the advances in imaging techniques there are still no easy answers. Imaging findings must be interpreted in light of the clinical findings and support rather than replace the neurologist or neuropathologist!"

Radiographic morphology of the cranial portion of the cervical vertebral column in Cavalier King Charles Spaniels and its relationship to syringomyelia. Stalin CE, Rusbridge C, Granger N, Jeffery ND. Am J Vet Res. 2008 Jan;69(1): 89-93. Quote: "Results suggested that radiographic morphology of the atlantoaxial region in CKCSs differs from morphology of that region in dogs of other breeds, but that these differences do not account for why some CKCSs develop syringomyelia and others do not."