Recognising feline pain: it's complicated!

We're also featuring our monthly JFMS Clinical Spotlight interview, and this month I'm speaking with Professor Clare Rusbridge about neuropathic pain in cats.

So it is a tool where you look at the cat's face and you look at five different characteristics, which we call action units. So this is, for example, the position of the ears, the opening of the eyes, the position of the head, we also look at the muzzle and the whiskers. So we look at these five action units and we give a score of 0, 1, or 2. 0 when it's normal, 1 when it's mildly changed or we're uncertain, and a score of 2 when it's clearly changed from the normal.

So if you have five characteristics and you can give a score of 2 for each, the maximum score of this scale is 10, and any cat that scores four or higher, it means that they are in pain and we need to do something about it. So for veterinary professionals, we're going to administer analgesics. And for cat caregivers, they should be prompted to go and take the cat to the veterinarian. So this is what the feline grimace scale is.

We now have eight studies published on the feline grimace scale, and we're understanding and doing all these studies and the limitations. And we were very curious to know, since this is a very simple and quick to use tool where you just need to look at the cat's face, you don't necessarily need medical training. You're just looking at changes in the facial expressions of the cat and giving scores. Could cat caregivers also be able to do this?Because if they can, that would be amazing, right?

It means that in the home environment, they can evaluate their cat and help them make decisions if they need to bring the cat to the vet, for example. So initially we did a study where we invited five very dedicated cat caregivers and they evaluated 100 images of cats with different degrees of pain and they would give feline grimace scale pain scores on these 100 images and they did that twice a few weeks apart. And from that study, we found that they were reliable.

So those cat owners, they could evaluate pain in cats just like most veterinarians will. But then the question was, these five cat caregivers are very dedicated. What about the average cat caregiver out there in the world? Can we really say that any cat caregiver can do that? So that was the purpose of this study that was awarded. It was really like going global and trying to reach the average cat caregiver population. So that was really what we did. So very briefly, we selected 10 images.

So remember in the first study we had 100. We had to make this simple, otherwise no one would participate. So we selected 10 images of cats from all of our previous studies. And then we invited these people to score these cats using the feline grimace scale. But they had to read the training manual that has all the images of cats and the different scores. And the survey was available in English and Spanish. And it was online and it was free for anyone that could participate.

With a couple of eligibility criteria. So we had to be over age and it had to be a cat caregiver to participate. So a llong response to why we came to this study, but it really was a journey trying to help understand how we can better evaluate pain in cats. And then how can we transport all this information that we're developing in the veterinary medicine world to the cat caregiver world?

There were no difference in scores between veterinarians and cat caregivers. And the other thing that we were actually very pleased to find was that regardless of the demographics, there were no effect on any of the demographics that we studied. So we looked, for example, at the age of the participant, the gender, whether they had worked in health medicine.

And whether they have previous experiences and none of the demographic variables that we investigated affected scores, so we were very pleased to see that as well. And I think what this translates to is that we can really extrapolate that pretty much any cat caregiver is able to reliably assess pain in cats using the feline grimace scale. So I think it speaks to the widespread global representation and that they're generally reliable to do that.

You can have, for example, a withdrawal reflex, just a reflex, after a painful insult to the foot. So if we clamp artery forceps over a toe, that's the usual way of assessing that. The foot can rreflexly withdraw even if the spinal cord is severed. But pain perception is that information getting all the way to the brain and the animal dealing with that information.

So a classic example of that in cats is cystitis, which I think would actually be usefully called feline bladder pain syndrome. So in this, we assume that there has been changes to the function of the nervous system that is making this chronic pain syndrome much amplified. So it's kind of central sensitization going on through the nervous system.

Another example, of course, is osteoarthritis, where the pain in that condition is amplified by having different function to the nervous system through the peripheral nerve, the dorsal nerve root ganglion and the spinal cord. And that is distinguished from true neuropathic pain where there is actually damage to the peripheral or the central nervous system.

So an example of neuropathic pain in the cat would be if they had orthopaedic surgery and the surgeon retracted the sciatic nerve and kept that retraction on for a long time and, give the sciatic nerve a little bit of a break if you have to retract it and not leave it retracted over a long period of time. So damage to that sciatic nerve can leave to postoperative neuropathic pain. We know there's actually damage to that nerve going on rather than a kind of theoretical concept.

The other term that we often use is maladaptive pain and that really is another term for really describing nociplastic pain as well.

However, there are neuropathic pain syndromes, like, for example, feline hyperesthesia syndrome, where if you did MRI, you would find nothing to help you do those diagnostic tests. So, that's just to say diagnosis can be very confusing in some cases. So, the other sort of arm is, that's the first thing actually demonstrating there is a lesion, the second thing is finding evidence of abnormal sensation. So what that implies is there is an abnormal functioning in your system.

For example, in the cat with a damaged sciatic nerve due to orthopaedic surgery, you may find that if you touch that area, they react really over the top, or they may have numbness. So it's one of the big ironies of neuropathic pain is that they may have less sensation, but be experiencing abnormal sensation. That would be one important facet.

And going back to that really challenging to diagnose case, the feline hyperesthesia syndrome, those cats behave as if they're experiencing abnormal sensation. Now, obviously that's trying to make a subjective assessment of a cat's behaviour, which is very unreliable. And then we have our diagnostic tests like MRI and electrophysiology. Those may help, help confirm.

But of course, especially in this time of economic downturn and crisis where people are managing cases on a budget or referral for those sorts of expensive diagnostic tests isn't an option then I think it's reasonable to add in there a positive response to trial treatment. So if you have a high index of suspicion, perhaps a two week course of trial treatment to see if there is a positive response.

Now, the negative side of that is that many of these drugs that we use will affect the cat's emotional state. And we've already talked about the connection between the emotional state and pain. And you could argue that in some of these cases, like feline hyperesthesia syndrome, where a lot of the cats are dealing with anxiety issues, and you think, are these signs related to stress rather than abnormal sensations? And they make a response to a drug.

And you think, was that just them being more relaxed in their environment? We don't know. And some people would argue, does it matter? We've got a happier cat, so maybe we've achieved the end without actually knowing the why.

to take that route.And as I mentioned earlier, you had some really nice case examples within this paper, which I found, for me, really helpful to just interpret the text of what you're saying and then how we would apply that into practice. So, thank you so much for your time today, Clare.

We'll be back again next month with another episode. If you don't want to miss out, do make sure you've signed up to Chattering with ISFM on your preferred podcast platform.