First ever guidelines published for diagnosis and monitoring of canine cognitive dysfunction

The Canine Cognitive Dysfunction Syndrome Working Group recently published their guidelines for the diagnosis and monitoring of canine cognitive dysfunction syndrome (CCDS) in JAVMA. These are the first such guidelines on the topic, and they were created through the work of an international panel of CCDS experts. 

In the guidelines, the working group defined CCDS and described some of the ways in which the syndrome can affect dogs’ quality of life. They also proposed two levels of diagnostic testing for dogs suspected of having CCDS, along with a severity grading scale comprised of three stages that can be used for both diagnosis and monitoring of the condition.  

Natasha Olby, Vet MB, PhD, MRCVS, DACVIM (Neurology), Professor of Neurology and Neurosurgery at the North Carolina State University College of Veterinary Medicine, led the working group as part of her lab’s canine neuro-aging program. She gave some background on the current state of CCDS diagnosis in dogs how she hopes the new guidelines will aid veterinary teams and clients in their understanding of dogs’ function.  

Barriers to CCDS testing and diagnosis in dogs 

Olby explained that evaluation of cognitive function in dogs is difficult for a variety of reasons, including lack of any definitive testing, the time constraints of typical veterinary exam, and the challenges posed by having to rely on human caregivers as a proxy for dogs in some cognitive testing protocols.  

“It’s hard to do [a battery of cognitive tests] in a primary practice setting, she said, due to the various distractions in a primary care setting, along with the time constraints associated with veterinary appointments.  

Other barriers include insufficient data from cognitive testing in dogs that would give more insight into what is normal and what is abnormal. “In people, we have tests that you do, with standard questions and they’ve been done in hundreds of thousands of people. So you know what a normal trajectory is and you know what’s deviating from that,” she said.  

Throw in the potential for breed variation in cognitive function over time, and it gets even more difficult to standardize normal and abnormal diagnostic criteria.  

Then there is the challenge of distinguishing between CCDS and other medical causes (like a brain tumor) that might cause similar signs.  

Diagnostic testing levels 

The guidelines propose two levels of testing that can be used to determine the likelihood of a CCDS diagnosis: a diagnosis based on history and clinical signs (level 1) and one that is made based on the results of brain magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) cell counts (level 2).  

The working group recommends using the DISHAA acronym to describe the behavioral changes often associated with CDSS. This stands for:  

• disorientation 

• impaired social interactions 

• sleep disturbances 

• house soiling, learning, and memory deficits 

• activity changes 

• anxiety and fear 

As a neurologist, Olby said that, in a perfect world, every dog would have a full diagnostic workup that included lab work, an MRI, CSF sampling, and possibly even histopathology of brain tissue. But she acknowledged that this kind of workup is not practical for many cases, either because of the cost of the workup or because the anesthesia needed would be contraindicated due to existing comorbidities. 

She stressed the importance of veterinary discretion to determine which patients should be recommended to have additional diagnostics done instead of assuming that the dog has CCDS. “These need to be old dogs,” she explained, and their history needs to fit with the DISHAA criteria. “You need to do a neuro exam,” she added.  

And in cases where veterinarians believe a dog might have an “alternative” diagnosis, they can offer a more thorough medical workup.  

 

 

 

Grading severity scale 

For dogs diagnosed with CCDS, the guidelines recommend a three-tiered grading scale modeled after human guidelines to determine the severity of a dog’s cognitive disease. It’s based on the client’s perception of the dog’s clinical signs and how they interfere with their quality of life, combined with the veterinarian’s assessment of the patient.  

The three tiers are: 

• Mild CCDS: behavioral changes are subtle and at low frequency or severity; the dog is generally able to perform normal functions; changes are frequently attributed to old age by caregivers and may be missed unless specifically screened. 

• Moderate CCDS: behavioral changes are more frequent and severe, interfering with normal daily activities and requiring management adjustments. 

• Severe CCDS: behavioral changes are overt and debilitating; the dog needs support even for basic functions, and comprehensive management is needed. 

While there are currently no definitive treatment options for CCDS, Olby said that having a grading scale can help not only standardize language for research purposes but also give families of dogs with CCDS more of a sense of what to expect and what to look out for over time. 

Additionally, she said there is still value in identifying CCDS early on, as interventions like therapeutic diets have been shown to help support cognitive function, and research is ongoing for other treatment modalities. 

Future diagnostic avenues 

Biomarkers 

Biomarkers are already used to diagnose diseases like Alzheimer’s disease in humans, but there aren’t commercially available biomarker tests for CCDS yet. Olby said her group has been studying them since at least 2019, and many other research groups are now as well.  

She said that biomarkers of interest belong to one of two different groups: structural proteins (also called synaptic proteins) from astrocytes and neurons that get released into the CSF and then make their way to the bloodstream and serve as an indicator of neuronal death, and disease-specific biomarkers (like amyloid beta) that are known to build up in the brains of humans and animals with cognitive dysfunction.  

One complication with measuring structural proteins is that they are present in the bloodstream in abnormally high levels not only in neurodegenerative diseases like CCDS, but also diseases like degenerative myelopathy. 

“We need to establish normal trajectories, normal concentrations at different stages of life across dog breeds,” she said, keeping in mind that an abnormally high result may not be specific to CCDS.  

Olby said that cost is also a factor in making biomarker tests more widely available.  

She added that research to make biomarker testing more practical is ongoing. “The trouble is that a lot of [that research] takes a long time,” she said. 

Cognitive testing 

Olby reported that several researchers have been working to develop cognitive tests for dogs, but so far there is no standardized option for practitioners to complete during a physical exam.  

The other factor to overcome is the time it takes to complete cognitive tests in a way that is reliable and helpful. As part of it, dogs have to be removed from any distractions and put at ease with the staff performing the tests. This usually involves a period of play and administering treats. Then they have to be taught the object of the “game” incorporated into the testing and be willing to participate for a meaningful determination to be made.  This all takes time.  

Olby said that some older dogs get tired and need to rest before the testing can be completed.  

During the COVID-19 pandemic, Olby said her team taught clients how to perform a sustained gaze test at home with their dogs, which worked well apart from interruptions from other pets or people in the home. She said this may need to continue going forward so that families can collect some data about their dogs’ cognitive function outside of their veterinary appointments.  

Future research 

Olby said there is “enormous interest and activity going on” with regard to CCDS. As part of this, she said multiple research groups the world over are working to answer questions about the best diagnostic steps and the best treatment options for cognitive dysfunction in dogs and other species.  

She also pointed out that what we refer to as CCDS is likely a variety of separate but related conditions with different etiologies. She said that just as in humans, where the term dementia is often used to refer to conditions such as Alzheimer’s disease, vascular dementia, Lewy body disease, and others, the term CCDS should be considered an umbrella term for multiple different syndromes in dogs.  

“In dogs we’ve tended to only talk about amyloid pathology, but the truth is we know they have vascular pathology as well, both amyloid and not,” she explained. “And we know on MRI that we see lots of little micro hemorrhages in dogs and we say that’s just often coincidental. We don’t really understand that.”  

Further research will hopefully shed more light on the individual syndromes that comprise CCDS and how to best support quality of life for our beloved aging canine companions. 

“Keep watching this space,” Olby said. “Because I think this field is going to move fast.” 

Further reading: 

A compassionate approach to feline cognitive dysfunction

One health connections: How feline cognitive dysfunction CDS research benefits from Alzheimer’s research

Photo credit: underworld111/iStock via Getty Images Plus 

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