Canine cognitive dysfunction (CCD), also known as dementia, is a common comorbidity in ageing arthritic patients. Studies estimate that around 28 percent of dogs between 11 and 12 years old suffer from varying degrees of cognitive dysfunction (Neilson et al., 2001). This figure increases with advancing age and is, in all likelihood, an underestimate as many of the changes caused by CCD are perceived as “normal ageing” by owners. Similarly, many owners assume that the signs of osteoarthritis, such as stiffness and loss of mobility, are to be expected in older or elderly pets. This unfortunately means that clients do not always seek veterinary advice.
CCD and osteoarthritis are often seen together and share certain features at presentation and, to some extent, in their treatment – both requiring a holistic approach for success. Disentangling and managing the effects of each disease is essential for us to effectively care for our older canine patients and offer them high-quality veterinary care in their senior years.
The brain is very susceptible to oxidative damage due to its high metabolic rate, relative lack of endogenous antioxidant processes and high percentage of polyunsaturated fatty acids. Oxidative damage leads to structural and functional changes, including a reduction in brain mass and the number of neurons, neuroaxonal degeneration, beta-amyloid plaques, the depletion of neurotransmitters and a further decline in endogenous antioxidants. These structural and functional changes are what we believe lead to the clinical signs associated with cognitive dysfunction.
In canine patients, we see several histopathological changes similar to those seen in human patients suffering Alzheimer’s disease.
As with arthritic patients, many pets suffering from CCD initially present at the vet for reasons unconnected with these conditions. The reason for attending the practice may be a routine healthcare appointment, such as a vaccination or an unrelated complaint. This makes it vital that we, as veterinary professionals, actively look for these diseases in our older patients and ask the right questions whenever they present to the clinic.
The specific signs of CCD are often known, and learned, through the acronym “DISHAA”, which stands for (Sung and Landsberg, 2020):
Other signs may include hearing loss, vision impairment and smell disorders. Dogs with CCD may also present with gait and movement disorders, such as proprioceptive deficits, tremors, swaying and falling.
Similarly, the arthritic patient may not initially present to the clinic with the disease as the main concern, and there are several areas of overlap between the presentation of CCD and osteoarthritis. In addition to the gait and movement changes that can be seen with these conditions, owners may report a reduction in social interactions, daytime lethargy, house soiling, restlessness and anxiety. Careful questioning of the owner, as well as a thorough clinical examination, will often help the attending veterinarian differentiate between these disorders and, in many cases, recognise when they occur simultaneously. In cases of the latter, a thorough investigation can also help differentiate the effects of each comorbidity on the patient.
Consultations with older dogs can prove tricky, particularly when a pet is “just” brought in for “a routine check-up”. Veterinary professionals should always conduct these consultations with empathy, and all communications with owners about any concerns and their possible implications must be clear.
During these check-ups, owners will not necessarily expect to receive the news that their pet is sick. Some may become upset, angry or defensive; they may be worried that they have missed something or concerned there is a suggestion that they have let their pet down in some way. This is where cultivating a strong vet–client bond is useful, as it will help you deliver the news and reassure owners not only that you are working in the best interests of their pet but that you are working with them without criticism or judgement. Communicating the findings of your examination can also help bring the client on board and make them feel involved in the process.
Clinical examination and patient history, alongside tools such as the canine dementia scale (CADES) questionnaire (Box 1), should form the basis of a CCD diagnosis in a similar manner to the way in which osteoarthritis is generally diagnosed. In all cases, a pain assessment is vital. The clinical examination also allows us to assess the patient for signs of other comorbidities or “red flags” that may point to more in-depth diagnostics being necessary.
| The CADES questionnaire, developed and validated by Madaria et al. (2015), is used to help diagnose CCD, differentiate it from normal age-related changes and monitor progress over time. It uses 17 questions divided into four areas that relate to changes in behaviour: spatial orientation, social interactions, sleep–wake cycles and house soiling. These are each assessed on a scale of 0 to 5, and the scores are added to obtain an overall score that reflects the degree of cognitive decline. |
It is important to consider CCD cases with a holistic approach. One example is the framework described by McKenzie et al. (2022), which encompasses many of the changes seen in older patients under the banner of “canine geriatric syndrome”. Considering older pets under this banner helps emphasise the need to consider the bigger picture at all times.
Other diagnostic tests that may be useful when diagnosing CCD include:
Early intervention is key with these patients, and the role of veterinary nurses and surgeons in detecting and communicating the early signs of disease is vital to optimally managing them. With both CCD and osteoarthritis, treatment should aim to slow the progression of the disease, improve mental and physical function where possible and maintain quality of life and the pet–owner bond.
Modification of the home environment and management of the ageing dog can often make a huge difference. Steps may include:
Feeding a good-quality diet with appropriate levels of high-quality protein to maintain lean body mass is essential. There is a small amount of evidence for some specific nutrient groups, including (Cotman et al., 2002; Kidd, 1999; Snigdha et al., 2016; Studzinski et al., 2008; Sung and Landsberg, 2020):
Pain control is essential wherever pain is suspected to be contributing to clinical signs, and multimodal approaches to pain management are commonly required. Careful consideration needs to be given to any medication that could make signs of CCD worsen, such as gabapentin which may cause mild sedation.
Selegiline can be used at a dose of 0.5-1mg/kg PO q24h for at least two months (Allerton, 2023). This has antioxidant and neuroprotective effects and can improve neurotransmitter function. It may also enhance learning and is indicated for use in CCD, especially when signs of anxiety and/or social withdrawal are seen (Ruehl et al., 1997).
Alternatively, propentofylline (at 2.5-5mg/kg PO q12h, 30 mins before food (Allerton, 2023)) is particularly useful in combination with selegiline and dietary management. It can improve cerebral circulation and has antioxidant and neuroprotective effects. However, this drug should be used with care in animals with heart disease.
Though not specifically indicated for CCD, clomipramine (at a dose of 1-2mg/kg PO q12h (Allerton, 2023)) improves neurotransmitter function, making it useful for the management of anxiety. Selegiline is contraindicated when clomipramine is used.
Collaborative care is vital to success in managing patients with canine cognitive dysfunction and its comorbidities. Regular check-ups with members of the clinical team should be scheduled to assess the patient’s progress and identify any problems. Pain assessments as well as regular weight checks should be carried out – these provide an opportunity for an ongoing assessment for cognitive and mobility changes, as well as time to reinforce education about home management strategies, nutrition and physical therapy with owners.
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