Ron Hines DVM PhD 4/24/06

The Disease:
With better nutrition, indoor accommodations and sophisticated veterinary care our pets are living longer and longer. Breeds of dogs age at strikingly different rates. For some reason, frail toy breeds seem to age the slowest while the large and giant breeds of dogs are often showing grey around their mussels when they are four. Some changes in old dogs are inevitable. All old dogs develop some degree of arthritis dimmed vision, aging of their ligaments, muscle atrophy, slower gait and less coping ability in new situations.

As dogs become elderly, they are also, to some extent, affected by a disease recently named Canine Cognitive Dysfunction Syndrome or CDS. A research study conducted in 1998 found that 48% of dogs 8 years of age and older showed at least one clinical sign associated with CDS. A study at the Veterinary School of The University of California found that 62% of 11 to 16 year old dogs had one or more behavioral categories indicative of CDS. Another study found that a bit more than half the dogs over 10 years of age and virtually all dogs 16 years of age or older showed some pathological signs of the disease.

When pathologists examine the brains of these animals they find some of the same sort of changes found in Alzheimer’s disease (beta-amyloid plaques) of human beings. It is marked by slowing down, confusion in facing new situations, forgetfulness and loss of learned behavior - particularly housetraining. Dogs are normally very aware of the boundaries of their yards. When CDS strikes, they will often wander past their normal boundaries becoming lost and confused. Canine Cognitive Dysfunction is caused by degenerative changes in your dog’s brain. As in Alzheimer’s disease, a proteinaceous material called beta-amyloid accumulates in there disrupting normal nerve pathways. The activity of a neural transmitting chemical, monamine oxidase increases while dopamine activity decreases.

Symptoms:
Dogs with CDS tend to be hyper-motile. They wander aimlessly or in circles and appear restless and confused. In advanced cases they seem to get lost in the house or yard and become trapped in corners or small spaces. They may bark or vocalize more than they used to and sleep in the daytime rather than at night. Some stare into space or at walls and have difficulty finding doors. They may become more timid or aggressive. Other pets are less enthusiastic about greeting their owners or no longer greet them at all. Although they may have been fastidiously potty trained during their life they start to loose housetraining or forget to let you know they need to relieve themselves until it is too late. This is the most common complaint that brings dogs with this condition to see me. They do continue to eat well and enjoy treats. They may forget people that they knew well. They seem to loose their train of thought and may just wander away while being petted or spoken too. They may forget their names.

Diagnosis:
Dogs showing these or similar symptoms need a complete panel of blood tests run on them because it is possible to confuse CDS with diseases affecting the liver (hepatic encephalopathy), low blood sugar (pancreatic tumors), kidney failure (uremia) and sluggish thyroid gland (hypothyroidism). Problems such as arthritis, heart disease, deafness and poor vision (cataracts) must also be ruled out. The diagnosis of CCD is through the absence of abnormal blood chemistry test results and physical examination.

Treatment:
A drug originally developed for human Alzheimer’s and Parkinson’s disease called selegiline hydrochloride (L-deprenyl) and marketed for dogs under the trade name Anipryl has proved helpful in treating some cases of this disease. Because this is a relatively new drug we are still learning about its effects. Some dog owner report near miraculous positive changes in their pets personality while on Anipryl while others note very few positive effects. Selegiline enhances the amount of chemicals within the brain that act as messengers between individual nerve cells. I give selegiline at 0.25-0.5mg/pound body weight every day in the morning it is also available in generic form. It appears that dogs given this drug for the rest of their lives do live longer. It can also temporarily reverse some of the changes of CDS. It can take up to sixty days to see an improvement so you must have patience. Some veterinarians also treat this condition with a supplement of omega-3 fatty acids because free radical compounds seem elevated in the brains of CDS pets.

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