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Cognitive Dysfunction Syndrome in Dogs

This condition, once called the senile or old dog syndrome, is a newly recognized disease, somewhat similar to Alzheimer’s disease in people. In dogs with cognitive dysfunction syndrome, the brain undergoes a series of changes that result in a decline in the mental faculties associated with thinking, recognition, memory, and learned behavior. Fifty percent of dogs over age 10 will exhibit one or more symptoms of cognitive dysfunction syndrome. Cognitive dysfunction is a progressive disease with increasing signs of senile behavior.

Disorientation is one of the principal symptoms of cognitive dysfunction syndrome. The dog appears lost in the house or yard, gets stuck in corners or under or behind furniture, has difficulty finding the door (stands at the hinge side or goes to the wrong door), doesn’t recognize familiar people, and fails to respond to verbal cues or his name. Hearing and vision loss must be ruled out.

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Behavior Changes in Aging Dogs

As they age, our dogs often suffer a decline in functioning. Their memory, their ability to learn, their awareness and their senses of sight and hearing can all deteriorate. This deterioration can cause disturbances in their sleep-wake cycles, making them restless at night but sleepy during the day. It can increase their activity level (resulting, for example, in staring at objects, wandering aimlessly or vocalizing more) or decrease their activity level (leading to less self-care and poor appetite)...

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Activity and sleep patterns are disturbed. The dog sleeps more in a 24-hour period, but sleeps less during the night. There is a decrease in purposeful activity and an increase in aimless wandering and pacing. Dogs with cognitive dysfunction may also exhibit compulsive behaviors with circling, tremors, stiffness, and weakness.

Housetraining is another area that suffers. The dog may urinate and/or defecate indoors, sometimes even in the view of his owners, and may signal less often to go outside.

Often, interactions with family members become much less intense. The dog seeks less attention, often walks away when being petted, shows less enthusiasm when greeted, and may no longer greet his family. Other dogs seem to need human contact 24 hours a day.

Some of these symptoms may be due to age-related physical changes and not to cognitive dysfunction. A medical condition such as cancer, infection, organ failure, or drug side effects could be the sole cause of the behavioral changes or could be aggravating the problem. Thus, medical problems must be tested for and eliminated before senile symptoms are attributed to cognitive dysfunction syndrome.

Research on the aging canine brain reveals a number of pathogenic processes that could account for many of the symptoms of cognitive dysfunction syndrome. A protein called B-amyloid is deposited in the white and gray matter of the brain and forms plaques that result in cell death and brain shrinkage. Alterations in various neurotransmitter chemicals, including serotonin, norepinephrine, and dopamine, have been described. Oxygen levels in the brains of senile dogs are decreased.

There is no specific test for cognitive dysfunction syndrome. The number of symptoms the dog exhibits and the severity of the senile behavior are important considerations in making the diagnosis. An MRI may show some degree of brain shrinkage, but the test is not likely to be done unless a brain tumor is suspected. Awareness of the diagnosis makes it easier to understand the dog’s behavior.

Treatment: The drug Anipryl (selegiline), used by humans to treat Parkinson’s disease, has been found to dramatically improve symptoms and the quality of life for many dogs with cognitive dysfunction syndrome. The drug is given once daily as a pill. Because medical treatment is now available, it is even more important to seek veterinary consultation for behavior changes in elderly dogs.

An additional benefit can come from feeding the therapeutic diet Hill’s b/d. This diet is specifically formulated with extra antioxidants for older dogs. Older dogs may also benefit from treatment with acupuncture and Chinese herbs.

WebMD Veterinary Reference from "Dog Owner's Home Veterinary Handbook"

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