This article is about more than Canine Cognitive Dysfunction (CCD), and if you were looking for an extensive exploration of the subject it will not provide that. There are much better places to find an in-depth discussion of the dementia that affects canines.
Sometimes we spend time mulling over events trying to get a glimpse of the future. It seems natural to believe that we can see trends emerge and follow those trends to their logical conclusion. My experience has been that that hardly ever happens. Still, we want to believe this story.
In my own life I theorized that since I took after my mother in many ways, am far sighted like her, had inequality in the amount of correction between my two eyes, and had "lazy eye" (amblyopia) as a child, that I would develop acquired macular degeneration like her, her sister and her brother. I did, but that wasn’t what took my sight. I lost my sight to NAION (non - arteritic ischemic optic neuropathy. I imagined that I would develop cancer someday since my mother and dad both had cancer, and wondered what type I would get. Nothing could have prepared me for getting what I did. Merkel Cell Carcinoma (MCC) is pretty rare. I get treated and followed at Duke Cancer Institute, and have for three years. A radiation oncology resident told me that Duke treats about 100 patients with MCC a year at Duke. By contrast, they treat thousands of patients with breast or lung cancer.
You don’t want to get a rare disease. No one is exactly sure how to treat rare diseases. I have two.
We inherited our daughter’s dog. It was a good thing for us and for Turtle, the dog. For seven years she lived with us, traveled with us, went for walks and seemed to enjoy life. The last year a lot of things changed. Turtle became “clingy”. She wanted to be with us all of the time. We would look up to see her at the doorway of a room she had never entered before asking to come in. She followed us into closets, the kitchen (something she had never done) and seemed confused at times. Her symptoms progressed and we put things together and decided that she had what veterinarians call Canine Cognitive Dysfunction.
She sometimes stopped and stared at walls, or into the fireplace, or walked in a circle through the house ignoring us as she passed by. She also lost her house training to some degree. We had to put down ‘pee pads’ in the den and once she lost control of her bowels. I convinced my wife that she was not going to get better, only worse, and the loving friend we had known wasn’t there anymore. After a few months we took her to the veterinarian and had her euthanized. I was unprepared for the sense of loss that we would both experience.
We were looking for another canine friend when we found that my Merkel Cell Carcinoma had metastasized to my brain. Since mid-February we have been driving back and forth to Duke. I had repeat studies, additional studies and surgery, and just finished a week of radiation therapy to the cavity where the metastasis previously lived. None of this was anticipated. What we have to look forward to now, is frequent trips to Duke (six hours one way) scans, and consultation with the various teams caring for me.
Our grandparents lived and died much more cheaply than we do. My mother’s parents were followed and treated for serious illnesses, but they didn’t have so many tests and visits. Perhaps that was because there weren’t as many options for treatment. Grandma had some heart condition that had greatly increased the size of her heart. Sitting at the breakfast table I can remember seeing her heart beat through her shift dress. She was being treated for high blood pressure and, as I remember it, she was on Hydrodiuril, Mercuhydrin, and something else. The Mercuhydrin was given weekly as an injection. Grandma was playing the piano when she dropped over at fifty-six. Her enlarged heart could have been due to hypertension, but I remember something about rheumatic fever with resulting heart valve damage causing it. I remember her cooking seeming tasteless. Mom told me that was because there was no salt used in cooking.
Today, Grandma’s doctor would have had access to many medications for hypertension and – if she did have a heart valve problem – they might have discussed cardiac surgery. However, I doubt that they would have, because Grandma died a decade before the advent of Medicare.
My other grandparents had similar, if less dramatic, health issues and outcomes. I have taken something for high blood pressure since the mid-1980s. At my last visit the radiation oncology resident took me off of it. I went in for a visit and my systolic blood pressure was very low. Dr. Chino was afraid that I would fall due to the pressure being so low. I would not have had computer directed radiation for the metastatic brain tumor. Up until a few years ago a metastatic brain tumor would have been treated with whole brain radiation. Imaging was less precise, and the whole brain was treated in an effort to prevent the growth of any other metastases. Today, they talk of “radio-surgery” treating each metastasis precisely. The problem with whole brain radiation was that it left patients impaired in subtle ways with memory and thinking. Chemotherapy has a similar effect in some instances; often enough to have given rise to the lay term, “chemo brain”. (“You better ask my husband; I have chemo brain.”)
My mother-in-law lived to 92. In the last few years of her life she developed dementia. It wasn't Alzheimer's Disease. She became suspicious, thought she heard people down the hall talking about her (using her maiden name), and accused people of stealing her clothes. Without describing her clothes I can assure you that the thieves would have had to be desperate. We could laugh about the things she said after we left the nursing home, but she was deadly serious in her belief that the conversations down the hall were real. The thing that disturbed my wife the most, I think, was that she began to use racist speech; something she had never done.
Our dog had Canine Cognitive Dysfunction which we were calling “doggy dementia” or “canine Alzheimer’s” before we found that CCN is a well-recognized syndrome in dogs. Veterinary medical journals have had articles discussing the clinical aspects of the disorder along with the frequency of symptoms and signs by age, sex, neutered status and found that the disorder increases with age over all categories.
It has been suggested that CCD could be used as a canine model for age related dementia in humans. Like human dementia which can be either primary as with Alzheimer’s disease or secondary as a result of some systemic disease, CCD can result from systemic illnesses like kidney failure which is quite common in elderly dogs. In both dogs and humans primary dementia is accompanied by amyloid deposits in the brain, which are seen in Alzheimer patients and in primary CCD.
In one study it was suggested that treatment with the mono-amine oxidase (MAO) inhibitor 1-depranyl might be used in both dogs and humans with no systemic source of dementia.
Our dog had kidney failure. The veterinarian who assisted in her euthanasia was of the opinion that both CCD and renal failure were common in elderly dogs, irreversible, and that our dog would continue to decline, even with treatment, and that we were doing the right thing. Doing the “right thing” was painful. My wife is still in mourning and will likely always be. Her comment when we came away from the veterinary hospital was, “I feel that we just murdered our friend.”
Amyloid plaque in Alzheimer’s disease
In primary CCD and Alzheimer’s disease there are similar pathological changes in the brain. Amyloid deposits have been a target of study because they are visible and increase over time with the dementia. There are several problems in studying and treating patients with these diseases; the diagnostic amyloid is not visible until after death, and no one really knows whether amyloid is a by-product of the process, or the cause of the cognitive decline.
One theory is that beta amyloid is a sticky trap for bacteria that come through the blood to the brain. It may protect the brain and the individual when the individual is young, but then contribute to cognitive decline as the number of plaques increase destroying the connections between neurons.