Growing old is a natural process and a fact of life, for all of us, including our four-legged family members. This is especially prevalent in dogs since they age faster than us humanoids. Family members will probably be the first to notice the subtle changes of Cognitive Dysfunction Syndrome or CDS. It may be more than just “getting old.” Dogs with CDS may show signs of confusion, forgetfulness, less responsiveness, and/or other various behavioral changes that are not a normal part of aging. These subtle signs might not be exhibited in the examination room so we may not see them during an examination.
CDS is believed to be caused by physiological and chemical changes in the brain of aging dogs that affect brain function. These may include accumulation of B-amyloid, declining neurotransmitter activities, or increased activity of monoamine oxidase-B, an enzyme that may catalyze the metabolism of dopamine.1
In MRI (Magnetic Resonance Imaging) studies of the head, images show black and white cross-section “slices” of the brain. In MRI studies of older dogs with CDS, we see changes when compared to MRI studies of younger dogs. In the images above, note the ventricular space enlargement (V arrows) and hippocampus tissue shrinkage (H arrows) seen in the older dog image on the left, compared to the younger dog image on the right.1
(not due to vision or hearing loss)
Appears lost or confused in familiar surroundings such as the house or yard
Gets “stuck” in corners or under or behind furniture
Stares into space or at walls
Has difficulty finding the door
Stands at the wrong door to go outside
Stands at the “hinge” (wrong) side of the door
Does not recognize familiar people
Does not respond to verbal cues or their name
Appears to forget the reason for going outside
|Activity and Sleep||Sleeps more in a 24-hour day (overall)
Sleeps less during the night
Decrease in purposeful activity in a 24-hour day
Increase in aimless activity (such as wandering, and pacing) in a 24-hour day
|Housetraining (for dogs previously housetrained)||Has “accidents” (urinates or defecates) indoors
Has “accidents” indoors in view of family members
Has “accidents” indoors soon after being outside
Signals less to go outside (for dogs who previously signaled/asked to go outside)
|Interaction with Family Members||Solicits attention less
Less likely to stand/lie for petting (walks away)
Less enthusiasm upon greeting
No longer greets family members (once the dog has realized that family members have arrived)
Since a biopsy of the brain is not usually a diagnostic option, a presumptive diagnosis can be made when there are clinical signs consistent with CDS and the absence of any underlying medical causes.
For a suspected case of CDS, as for any behavior problem, a history, physical examination, and diagnostic tests are needed to rule out the presence of any medical conditions that might affect behavior. These might include diseases of the internal organs, especially liver, kidney, and heart.
Additionally, primary and secondary behavioral problems need to be ruled out such as separation anxiety, noise phobias, or housesoiling.
Medical Conditions with Behavioral Components:
|Medical condition||Associated clinical signs|
(loss of sight, hearing, smell)
|Increased irritability, fear or aggression
Changes in sleep-wake cycle
Decrease in greeting behavior
Inattentive, decreased responsiveness to verbal commands
Urinary tract disease
|Incontinence, loss of housetraining
polyuria (urinating more)
polyphagia (eating more)
stranguria (painful urination, straining to urinate)
pollakiuria (urinating more frequently)
|Weakness, reduced mobility and activity
Increased pain, irritability
Possibly inappropriate elimination
|Decrease in activity
Increased irritability or aggression
Reduced tolerance to cold
|Polyphagia (eating more), polyuria (urinating more), restlessness
Decreased social interaction, responsiveness to commands and greeting behavior
Loss of housetraining
Disrupted sleep-wake patterns
(primary or secondary
|Changes in sleep patterns, eating habits, housetraining, aggression, docility|
To obtain a complete medical and behavioral history, we may ask many questions because signs of CDS may be subtle and not be exhibited in the examination room during during an examination. A printable Senior Dog Behavior History Form to aid in diagnosis of CDS is available by clicking here.
We will perform a thorough physical examination. In addition, a brief neurological examination will include assessment of cranial nerves, evaluation of postural reactions, especially conscious proprioception, and evaluation of the perineal reflex to assess sphincter function.
Typical diagnostic tests would include a serum chemistry profile, complete blood count (CBC), and urinalysis. Additional tests may be warranted based on the patient’s history and physical examination results.
Another method of diagnosis is response to therapy. If your dog improves when treated then there is a good chance he has this disease.
Anipryl® is a medication, in tablet form, generally given once a day. We will recommend the appropriate dose for each individual patient. You can learn much more about it by clicking on the link.
1. Cognitive Dysfunction Syndrome and Other Geriatric Behavior Problems; CE Advisor a supplement to Veterinary Medicine, Feb 1999.[view PDF format].
2. Controlling CDS with Anipryl®: Post Approval Field Research Results from Private Hospitals in the US; Pfizer Animal Health Technical Bulletin, Dec 2000. [view PDF format]
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- Adding New Science to the Practice of Medicine – Senior Dog Health, canine Cognitive Dysfunction Syndrome and anipryl® Senior Health Care advisor Program, Pfizer animal Health
- Campbell, S; Controlling CDS with anipryl®: Post approval Field Research Results from Private Hospitals in the US; Pfizer animal Health Technical Bulletin, Dec 2000.
Developed for Long Beach Animal Hospital, by Glenna M Gobar DVM, MPVM, MS, courtesy of Pfizer Animal Health; Sept 2001