Canine cognitive dysfunction and its relation to osteoarthritis: common comorbidities in ageing veterinary patients - Veterinary Practice
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Canine cognitive dysfunction and its relation to osteoarthritis: common comorbidities in ageing veterinary patients

Disentangling and managing the effects of canine cognitive dysfunction and other comorbidities in ageing dogs is essential for us to offer high-quality veterinary care to our senior patients

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.

Pathophysiology of canine cognitive dysfunction

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.

Clinical signs of canine cognitive dysfunction

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. 

It [is] 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):

  • Disorientation – getting lost in familiar surroundings, getting stuck or not recognising people
  • Social interactions – becoming more irritable or fearful with others and showing less interest in initiating interactions
  • Sleep/wake cycles – pacing and restlessness at night; lethargic and sleeping more in the day
  • Loss of housetraining – experiencing problems with learning and memory and displaying a loss of learned behaviours
  • Activity – showing repetitive behaviours and restlessness alongside a decrease in play and exploration
  • Anxiety – developing separation anxiety and a fear of new places, with increased reactivity to visual and auditory cues

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.

Diagnosing canine cognitive dysfunction

Clinical examination

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.

Cultivating a strong vet–client bond is useful, as it will help you […] 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

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.

Diagnostic testing

Other diagnostic tests that may be useful when diagnosing CCD include:

  • Blood (haematology and biochemistry) and urine (dipstick, SG, culture and UPC) tests to check for other underlying diseases and metabolic causes that may affect treatment choices
  • Systemic blood pressure checks
  • Radiographs to rule out other causes of pain in selected cases
  • Advanced imaging, such as magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) analysis to rule out other neurological conditions. These tests may also show the characteristic changes in brain structure and function in cases of cognitive dysfunction

Management of canine cognitive dysfunction alongside osteoarthritis

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.

Enrichment and home management

Modification of the home environment and management of the ageing dog can often make a huge difference. Steps may include:

  • Easier access to resources such as food and water
  • Increased frequency of toilet trips
  • Improved bedding and padded surfaces
  • Keeping a regular routine
  • Avoiding hard, slippery floors (using rugs, yoga mats or similar materials)
  • Use of feeding puzzles and other forms of mental stimulation/behavioural enrichment, especially when walks are limited by mobility
  • Retraining with modified cues that account for changes such as hearing impairment and reduced mobility
  • More frequent but shorter exercise sessions outdoors, with aids such as pushchairs when mobility is severely limited
  • Thundershirts to help with anxiety 
  • Physical therapy and massage – this enhances the pet–owner bond and provides mental stimulation as well as support for osteoarthritis

Nutritional interventions

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):

  • Antioxidants – studies have shown that diets high in appropriate antioxidants can slow cognitive decline and improve cognitive function
  • Alpha lipoic acid and omega-3 fatty acids – these have been shown to enhance mitochondrial function, reduce inflammation and promote cell membrane health
  • Medium-chain triglycerides (MCTs) – these triglycerides improve energy metabolism, improve mitochondrial function and provide ketones as an alternative energy form for the brain
  • Phosphatidylserine – studies have shown that this chemical is neuropositive and can regulate the fluidity of cell membranes and enhance cholinergic transmission
  • N-acetyl-L-carnitine – this form of L-carnitine helps enhance mitochondrial function and improves long-term recall in ageing canines
  • B vitamins – studies show that B vitamins are needed to form methionine which is then converted to s-adenosyl-methionine (SAMe), a cosubstrate important for normal brain development, function and neuronal health. B vitamins also act as cofactors in the synthesis of various neurotransmitters

Pharmacological interventions

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.

Pain control is essential wherever pain is suspected to be contributing to clinical signs, and multimodal approaches to pain management are commonly required

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.

What can veterinary teams do to support CCD patients and owners?

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.

Where can I learn more about all this?

If you’d like to learn more about other chronic conditions in an engaging way, then why not attend the inaugural Chronic Pain Symposium? Canine Arthritis Management have teamed up with Elearning.Vet to provide this three-day virtual symposium from 5 to 7 April 2024. It’s for all stakeholders – the global veterinary sector and pet professionals alike.

Gain some top-notch CPD by attending the discussions, lectures and bite-sized pre-recorded webinars on topics ranging from contextual care plan design and clinical reasoning to approaches to pain management from specialists, experts and companies worldwide. The primary goal of the event is to provide the best welfare through excellent pain management and to raise awareness of and help address chronic pain in our beloved patients.

With 14-hour-a-day coverage, the symposium is bringing a live event to every time zone, with subtitled translations available in over 30 languages. Even better – attendance is free! Or for a VIP fee, you’ll receive recordings of the sessions! Tickets for the event can be booked online until 29 March.

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