Breeding recommendations on syringomyelia


These are the current breeding recommendations and were issued in February 2007, after being agreed upon by neurologists and researchers who attended the International Conference on Syringomyelia, London, November 2006

Revised CKCS MRI screening and breeding recommendations

These breeding recommendations are made using current information and in response to CKCS breeder request for guidelines. It has yet to be proven if this guide is appropriate. The aim of these recommendations is to reduce the incidence of symptomatic syringomyelia (SM) in the breed, not to create litters of puppies guaranteed not to have SM as the chance of producing an affected dog cannot be predicted without knowing the inheritance.

Notes

The age cut off at 2.5years has been decided so as to tie in with MVD recommendations (see below) and because most
dogs with symptomatic SM will show signs before 3 years of age.

The following categories from the previous guidelines have been removed because of difficulty in accurately
interpreting
Previously A * - now A
Previously B – now C

It is recommended :

1) That both the sire and the dam of a proposed mating are screened (any unscreened dog should
be assumed to be “D”)

2) Offspring of any mating should also be MRI screened before breeding.

3) Any dog screened before 2.5 years old has a second screen when older.

4) That dogs are screened from 6 months of age

5) That if a limited (“mini”) MRI screen is performed that

a) the minimum area covered is from the level of the interthalamic adhesion to cervical
vertebrae 5 (C5)

b) Both TW1 and TW2 sagittal images are obtained in addition to TW1 and /or TW2
transverse images through the upper cervical spinal cord
.
c) An assessment is also made for presence/absence of ear disease and ventricular
enlargement.

6) That interpretation of images is made by Diplomate level radiologists, neurologists and, in special circumstances, by surgeons with recognized expertise in this area.

GRADE AGE (Years) SYRINGOMYELIA BREED TO
A Over 2.5 Absent or less than 2mm central canal dilatation in the C2-C4 region only A, C, D
C Under 2.5 Absent A and re-scan after age 2.5
D Over 2.5 Present but Asymptomatic A
E Under 2.5 Present but Asymptomatic Do not breed
F Any Present and Symptomatic Do not breed

Notes :  These recommendations will only work if cavaliers are actually MRI scanned!!
 
* MVD - to pass the MVD protocol, a dog must be free of systolic murmur over 2.5 years old with systolic murmur-free parents over 5 years old

* Occipital hypoplasia can be difficult to define because, in comparison to other toy breeds, the back of the CKCS skull is smaller - i.e. "normal" is very hard to find. In addition the term 'too small' has not been defined neither is there a consensus on how to measure the occipital bone. Basically there are 3 classic features of the malformation  i) loss of the normal round shape of the cerebellum which can appear indented by the occipital bone ii) displacement of the cerebellum into and through the foramen magnum i.e. herniation iii) kinking of the medulla.  Mild occipital hypoplasia is defined as a displacement cerebellum into the area of the foramen magnum and slight kinking of medulla and indentation of the cerebellum.
 
* Dogs may develop signs of syringomyelia at any age e.g. a dog can be free of pain until 7 years old i.e. dog's status may change as it gets older.

* Any dog not MRI scanned is assumed to be grade D or E depending on their age

* Breed clubs should consider whether to recommend that stud dogs are MRI scanned. Males have most influence on the gene pool (popular champions sire hundreds) and by the time it is known that a dog may pass on the tendency his genes may be widespread. It would be sensible that if a male dog to be used more than twice then, for the safety of the breed, he should be A or B. It would perhaps be a good use of research funds to use them to subsidise testing of stud dogs and publish a clear list. A salient fact is that 93% of top stud dogs in the UK are closely related to 1 or more dogs with SM and the pedigrees of these dogs are similar to Champions worldwide.