Thinking aloud about hydrocephalus in the thread on deafness, and doing a bit of internet research has had one interesting result - I'm now fairly sure that one of my earlier Cavaliers had CM and hydrocephalus, but not, as far as I know, SM. Be warned, this is a long post!
Rowley was a black and tan dog that I got as a puppy through Midland Club Rescue in about 1993. He was listed with rescue because his well-known breeder said she wanted a very particular, experienced Cavalier owner for him. He had been born with an enlarged fontanel (the hole in the skull above the eyes in many mammals - including human babies - which allows the skull to adjust to pressure during the birth process) as the runt of a litter of three, and because he was fragile had not been handled very much or allowed to play with the other dogs; there was also possible brain damage. As you can imagine, by the time I got him at 4 months, he was one difficult puppy! But in retrospect so much of his behaviour and problems can be explained by hydrocephalus - yet no one in our large veterinary practice ever suggested it (though to be fair, they dealt with his physical needs rather than his obvious mental problems - dealing with these I had to make up as I went along! And this was before MRI scanning was common, so diagnosis was difficult).
These are some of the symptoms of hydrocephalus listed on the internet:
A dome-shaped head: Rowley definitely had this - a friend who has bred both Cavaliers and King Charles took one look at him as a puppy and said 'That's a Charlie!'
An open fontanel which doesn't close at it normally would: Rowley had this.
Smaller than littermates and slow to grow: Rowley was tiny and never weighed more than 15 lb - I struggled to get him over 12 lb until he was about 2.
Slow to learn - very difficult to housetrain, for example: definitely true of Rowley, he never really got the housetraining message, and sometimes looked so bewildered and puzzled by life that I wept for him. On the other hand, how to you housetrain a dog (a Cavalier!) who is completely indifferent to people and not interested in titbits?!
Problems with vision: I'm fairly sure that Rowley didn't focus properly and often saw double. For example, he was very hesitant about going down stairs - because I think he saw two steps and didn't know which one would support his weight. I put this down to his fontanel problems having pushed his eyes quite wide apart, so that he couldn't focus them, but it could have been hydrocephalus?
Perhaps the oddest thing about Rowley was his indifference to people - so unusual for a Cavalier. It was about a year before he would come out of his bed to greet me in the morning with a wag of his tail, and he hated being picked up (REALLY hated - if you grabbed him too quickly, he turned into a snapping, snarling fury, and I soon learnt to pick him up behind his shoulders with his face away from me to avoid a bitten face!). Teaching him to come when called was a matter of insistence for his own safety - left to himself he would just stand and glare at me. He gradually improved, mainly thanks to my discovering his passion for raisins (no intolerance to them here!) and asking everyone we met to give him one, and by the time he died of sudden onset MVD at almost 10, he was beginning to enjoy being picked up and cuddled. He was the most difficult dog I have ever owned, but he could also enjoy life, especially country walking and pottering around the garden. I still miss him, especially that I had such a short time when I could cuddle him. Hydrocephalus explains so many of his oddities, though at the time I simply put them down to his early lack of socialisation.
Kate, Oliver and Aled