Ask a Vet: Can Dogs Develop Alzheimer's?
A while back I fielded a question from a concerned client whose 17-year-old Poodle had recently been diagnosed with heart failure after suffering a near-fatal crisis of respiratory distress. Fortunately the dog responded well to treatment and was able to go home on three heart medications.
Several days later the client contacted me. His dog was breathing normally, was able to be active, and was not coughing. But the dog was not behaving normally. The dog seemed agitated and was pacing in circles. He no longer responded to his name, but he did not appear to be deaf. He was not sleeping much -- he would drift off, and then his agitation would return. The owner wanted to know whether the symptoms could be side effects of one of the medications.
I've been a vet long enough to realize that I'll never see it all. I've also learned that anything is possible, and that one should never say never. Therefore, I couldn't state definitively that the medications (benazepril, furosemide, and pimobendan) were not causing the symptoms. But I could say that it was very unlikely. I have extensive experience with all of these medications and their side effects, and I have never seen any of them cause agitation, disorientation, and insomnia.
It sounded to me like the dog was suffering from cognitive decline, also known as dementia. Elderly dogs are prone to the problem. In fact, the condition has a name: canine cognitive dysfunction syndrome, or CCDS. The owner wondered, reasonably, why the symptoms came on so suddenly.
I was reminded of the first time I encountered an individual with cognitive decline, several decades ago. That person was an elderly (human) relative. She fell and broke her hip; she required surgery. The doctor told her daughter that she would never be the same again. I scoffed at the notion: It was a broken hip, and it could heal. Sadly, the doctor was right and I was wrong. The hip healed, but dementia set in rapidly after the accident; the individual was never able to live outside of an assisted living or memory care center again. The fall was a triggering event that unmasked cognitive decline that had been brewing for years.
In the case of the dog, I believed that the heart failure crisis was a similar triggering event. However, without personally evaluating the dog I couldn't be sure. The owner declined an examination.
Even if I had examined the dog, I still would not have been able to be sure. Cognitive decline is a devilishly tricky thing to diagnose. Heck, cognitive decline is hard to diagnose in people, despite the availability of cognitive function testing (trust me, I know a person with unquestionable dementia who has beaten just about every test out there). Dogs can't take cognitive function tests.
What is cognitive decline in dogs? It is not the same thing as Alzheimer's disease. Dogs' brains are not known to acquire amyloid plaques (although their brains also aren't routinely examined post mortem, so maybe the plaques are there and we just don't know about them). However, cognitive decline is similar to Alzheimer's disease. It is a condition of brain and cognitive deterioration that occurs in elderly dogs. Affected dogs may forget their names, get lost in their own homes, pace and circle, or fail to recognize their owners. Some early symptoms include failure to greet owners at the door, and wandering into the yard and then freezing, staring blankly into space.
As I mentioned, it's hard to diagnose. The symptoms may be subtle. Also, several medical conditions can cause similar symptoms. For instance, dogs with hearing loss may not greet their owners at the door because they may not realize anyone's there. Problems with the liver can cause behavioral changes because of a condition called hepatic encephalopathy. Brain tumors, meningitis, and encephalitis can cause symptoms similar to those of cognitive decline. And although furosemide, pimobendan, and benazepril do not frequently cause disorientation, other medications such as certain narcotic pain killers and medications that treat epilepsy can.
Here is the bad news: The condition is progressive (in other words, it gets worse with time), and there is no truly effective treatment. A medication called Anipryl (also known as selegeline) was aggressively marketed for the problem about a decade ago; however, I received mostly negative comments from clients whose dogs took it. A special cognitive diet, b/d (by Hill's) also is purported to help with the problem; the clients I know who have tried it have been highly nonplussed.
Fortunately, there is also good news. Dogs suffering from canine cognitive dysfunction syndrome generally do not experience the devastation that is wrought by Alzheimer's and other similar conditions in people. Most are able to live out their lives in relatively normal fashions. This is largely because dogs are not expected to function at the same cognitive level as people. It may also be partly because of the nature of the condition: Dogs' brains simply may not be destroyed as completely as those of people with dementia.
If you suspect your older dog may be experiencing cognitive decline, the first step is to get a veterinary checkup. As I mentioned, several diseases can mimic the condition. Some of these are serious and require treatment. The vet will probably recommend blood work or other diagnostics. If a diagnosis of CCDS is made, take comfort from the fact that the condition is not likely to devastate your dog.
Read more by Dr. Eric Barchas:
- Why Do Some Dogs Keep "Showing Their Lipsticks"?
- Let's Talk About Dogs and Euthanasia: When Is It Time? Should You Be Present?
- What to Do Before You Get to the Vet in 12 Emergency Dog Situations
- 12 Dog Emergencies That Need Immediate Veterinary Attention
- Just How Dangerous Is It to Falsely Call a Pet a Service Dog?
Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)