Is SM hereditary? The answer may seem obvious -- that it is -- but doubts have been raised. In Bet Hargreaves' October 2005 update of her Syringomyelia Blog on she questions whether SM is due to genes or genetic factors. She writes:

"Is Syringomyelia hereditary? Why I ask the question has it been proved scientifically in Cavaliers that Syringo is hereditary is because in a veterinary paper published in 2004, it was stated by the researchers into the problem in Cavaliers all the affected Cavaliers researched had at least 6 of 8 Gr-grandparents that could be traced back to a common female ancestor born in 1956, whereas only 6.6% of unaffected Cavaliers had this ancestry.

"There has now been a list published of Cavaliers who have been M.R.I scanned and are showing no sign of SM but at least 6 of 8 of their Gr-grandparents also can be traced back to the same common female ancestor born in 1956. To add further doubt as to whether SM has been proved to be hereditary in Cavaliers, researchers at Duke University, America into the human form of the same condition for around 3 years, say that it will be at least several more years yet before it can be said as to whether it is due to genes or genetic factors. Because of this information, for the benefit of the Cavalier breed, should the first priority be to prove that SM is hereditary in Cavaliers."

Then, in Dr. Dewey's October 2005 article in JAVMA (along with Drs. Bergm Barone, Marino, and Stefanacci), they state: "There is strong evidence to suggest that COMS is a heritable condition in Cavalier King Charles Spaniels." They cite earlier articles by themselves, Clare Rusbridge, Penny Knowles, and Drs. Lu, Pfeiffer, and Targett as authorities for the evidence.

As a layman, on one hand, I wonder why anyone would doubt that SM is hereditary, considering the wide range of lines of Cavaliers with either SM or COMS or both. But then, even the neurologists currently studying the disorder -- Drs. Dewey et al -- only go so far as to say that there is "strong evidence" to suggest it. What does it take to tip the scales toward or away from heritability?

Rod Russell
Orlando, Florida USA