Good points Cathryn and Bet. And worth adding again that just because a cavalier has SM does not mean it must be removed from a breeding programme -- unless it is symptomatic. People keep forgetting this. The dog may receive a lower grade, but can still be bred to an A dog. Even an A dog can have a small syrinx (whch *I* keep forgetting! :lol. It is important for breeders to retain a wide range of good genes and a good heart for example may make a D dog an important dog to retain in a breeding programme. So far, results of breedings to A dogs have been very good and no known AxA crossing has yet produced puppies with SM. Dutch breeders in particular are doing some very controlled breedings, and also some in the UK and the US.
Grading table:
GRADE, AGE (Years), SYRINGOMYELIA, BREED TO
A: Over 2.5; Absent or less than 2mm central canal dilatation in the C2-C4 vertebrae 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
Grading table:
GRADE, AGE (Years), SYRINGOMYELIA, BREED TO
A: Over 2.5; Absent or less than 2mm central canal dilatation in the C2-C4 vertebrae 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