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
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.
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)...
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
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.