Laurent Cauzinille, DMV, Ecole Nationale Veterinaire de Maisons Alfort, Paris, France
Neurology and Neurosurgery Department, Centre Hospitalier Fregis, Arcueil, France
“Incidence of caudal occipital malformation syndrome and ultrasound, computed tomographic, magnetic resonance imaging findings in 16 clinically normal Cavalier King Charles Spaniel genitors”
Authors: Jerome Couturier, Delphine Rault, Laurent Cauzinille
“We had two years ago, what we called ‘the French exception’. There was ‘no SM in France’,” Cauzinille said. The French CKCS club referred to SM as ‘the British CKC disease.’ Then, a couple of cases appeared and now there are more than 25 known cases.
In November 2004 he gave the first lecture and produced an article on SM in cavaliers. In June 2006, the French club accepted his proposed study, which was small but with two key French breeders, conducted at the the Vet Imaging Centre in Paris.
* 16 dogs in the study
* all were clinically and neurologically ‘normal’ according to their breeders (who filled in a questionnaire) and verified by neurologist’s tests (but not MRI)
*all were LOF (French kennel club pedigree) and breeding dogs
* Dr Couterier performed the neurological clinical testing, which included checking for: cervicalgia, hyperesthesia, scrathcing, ataxia, paresia, abnormal head posture, scoliosis, strabismus, facial paralysis, cranial nerve deficit
A number of study tests were then done.
*Ultrasound was performed on awake dogs with the goal of trying to find a less expensive screening test. Diameter of the spinal cord was measured at C1/C2 and at the level of the foramen magnum with the head flexed 90 degrees.
* Dogs were then anaesthetised, and a spiral CT scan was performed from the tuberculum sellae to the dens of the axis. Sagittal, transverse and dorsal images were taken (which is quite extensive). Linear measurements and area of the caudal fossa were obtained in the sagittal plane; height of the foramen magnum; area of the caudal fossa. In the transverse plane at the level of the widest part of the caudal fossa, linear measurement of the maximum width of the fossa was obtained.
*Then, dogs were MRId in a dorsal recumbent position using a 0.3T MR system -- the skull to the 1st thoracic vertebrae. If there, they measured hydrocephalus, ventricles, cerebellar size and degree of herniation.
As a result of these tests, the population was divided into groups: 1) normal; 2) syrinx; 3) hydrocephalus but no syrinx.
1) normal dogs: 8, 7 males and 1 female -- but had Chiari-like malformation
2) syrinx: 7 had SM, 3 males and 4 females, “a big shock to the breeders”
3) hydrocephalus but no syrinx: 1 male
In all the dogs, no statistically significant difference was found in the measurements taken except in the hydrocephalic dog. With this group, 43% of clinically normal champion breeding dogs (genitors) have SM “so there’s no more ‘French exception’.” But this is only 16 dogs so researcher cannot give a percentage affected for France, but these were were all pedigree dogs representing 6 key breed lines all with common ancestors.
* There was no association between the degree of herniation and SM. Doesn’t know if size of caudal fossa matters.
*They were able to pick up syrinxes with ultrasound
* They will repeat MRIs on the French dogs in 1 year and 3 years. He hopes King Charles Spaniels can be included in future research.
* The doctor doing the ultrasound was impressed with how much of the cerebellum could be seen with ultrasound.
* He thinks the next step is to keep looking at CSF dynamics -- “the thing that will really help us to progress a lot.”
Harvey Carruthers, BVMS MRCVS
“Association between cervical and intracranial dimensions and syringomyelia in the Cavalier King Charles Spaniel”
The aim of this study was to establish is intracranial and vertebral measurements can predict the occurence of SM. The study tested the hypothesis that SM results from caudal fossa overcrowding and is influenced by cervical vertebral abnormalities.
MRI scans of 85 CKCS were reviewed. Seven dogs were excluded because of missing or incomplete MRI data.
* Of 78 dogs, 59 had syrinxes; average age of dogs at time of MRI= 3 years+/-2.05. “SM in cavaliers is predominantly a young animal problem.” But older cavaliers were more likely to have a syrinx.
* dogs without syrinxes were used as controls
*MRIs were made anonymous when reviewed (so no one knew the specific dogs they were viewing) and read by three people at two sites
* the three paper authors studied sagittal and transverse T2 -- weighted images -- for the presence or absence of syrinxes
Cervical measurements: they took top to bottom height measurements of C2-C3 vertebrae, then measured the angles on the C2-C3. Specifically:
* the caudal fossa base length and height were combined to give a measure of caudal fossa volume (“the caudal fossa triangle”).
*the widest vertical diameter across the spinal canal, at C1/C2, at C2, at C3; the widest point across the C2/C3 joint; and the angulation of the C2/C3 spine were measured
* These measurements were compared to those of dogs without SM
There were no significant correlations between the caudal fossa volumes measured and incidence of SM, except for reduced volume. But there were some interesting measurements in cervical width of C2-C3 junction associated with the presence of syrinxes, and also between the width of the widest point of C3 and the presence of syrinxes.
* A greater width at C2/C3 is associated with a syrinx
* A greater width at C3 is associated with a syrinx: this was a surprise finding fro the group
These results may contribute to the predictability of syrinx occurrence. They could possibly also help in the development of testing for SM not reliant on MRI (eg x-rays). Further study is planned to see if cervical findings are significant in the parthenogenesis of SM
There was a significant difference in the C1/C2 diameter between dogs showing pain and those without pain.
* The presence of pain is associated with the narrowest point from C1/C2 to the dens
* Dogs with pain had the narrowest measurement of .93cm versus .99cm for no pain
Nick Jeffery, BVSc PhD CertSAO DSAS (ST), DipECVN, DipECVS, FRCVS
“Association between spinal cord dorsal involvement and pain in syringomyelia secondary to canine Chiari malformation”
This study was designed to test the hypothesis that pain associated with SM is related to spinal cord dorsal horn damage, and look at the relationship between pain and syrinx dimension.
* Commonly localized to head or neck
* May be difficult to define or intermittent
worse at night
when first getting up
may vary with atmospheric conditions
related to posture
* May be sensitive to touch
* Can scratch at shoulder, ear, neck or sternum
typically one side only
whilst moving, often without skin contact
Is pain associated with damage to the dorsal horn? To find out, researchers need to correlate signs of pain with syrinx dimension. The top part of the spinal cord is where pain is processed.
Looked at the size and location of syrinxes in 85 CKCS from measurements made over a two year period (60 from breeder screening programs). 11 dogs were excluded leaving 74, 60% female. Images were coded and viewed independently by three of the authors of this paper.
Is there a syrinx? If so:
* measured the maximum width of the transverse image (any angle)
* is there dorsal or ventral asymmetry?
* if syrinx is asymmetrical, how long was the asymmetry (the reason to look for this is that it has been associated with pain in humans with SM)
* 55 of 74 CKCS had syringomyelia
35% SM were painful
27% SM had scratching behaviour
* Comparison pain SM and no pain SM
No correlation sex or age
Strong association with maximum syrinx width (p<0.0001)
Dogs in pain - mean maximum width 0.58cm
Dogs without pain - mean maximum width 0.32cm
95% of CKCS with SM greater/equal to 0.64cm were painful
There is a very strong association between maximum syrinx width and pain:
* Asymmetry of syrinx is only found in the dorsal half of the spinal cord, and is associated with pain. 79% of dogs with pain had such a syrinx.
* syrinx length is also associated with pain.
Results – dorsal asymmetry:
* Syrinx asymmetry only found dorsal half spinal cord
* Dogs in pain more likely to have dorsally asymmetrical syrinx
15/19 (79%) - dogs with pain
16/33 (49%) - dogs without pain (p=0.0419)
* Mean length of asymmetrical syrinx
5.15cm - dogs with pain
2.8cm - dogs without pain (p=0.0039)
But the association of length with pain is not significant when correlated with width. The strongest predictor of pain is syrinx width.
Disordered neural processing in the damaged dorsal horn is a likely consequence of SM and can cause neuropathic pain that often responds poorly to conventional analgesics.
* Syrinx width strongest predictor of pain
95% of CKCS with SM greater or equal to 0.64cm are painful
* SM likely to cause neuropathic pain
Signs of SM suggest
Dysaesthesia - unpleasant abnormal sensations
Allodynia - pain due to a stimulus that does not normally provoke pain e.g. simple touch
Hyperalgesia - increased response to a painful stimulus
* Dogs tend to scratch to the side of syrinx asymmetry. This is due to an inbalance in input to the thalamus
* Doesn’t think it is possible to pick out heads more likely to have SM