Rethinking Neurological Exams in Guinea Pigs: Why One Size Doesn’t Fit All

Guinea pigs don’t read the dog-and-cat neurology textbook and that’s exactly where clinicians get into trouble. We sit down with Dr. Vishal Murthy to unpack what a truly species-specific neurologic examination looks like for guinea pigs, why so many “standard” tests can be misleading, and how prey-species stress can flatten reflexes and hide both normal function and real disease. If you’ve ever felt unsure interpreting postural reactions or reflex testing in small mammals, this conversation gives you a clearer baseline for what normal actually is. 

We dig into the practical realities that make exotic pet neurology hard in the exam room: freezing, shutdown behaviors, and the ways restraint and stress can change responses. Vishal shares the most surprising findings from their work, including why a gag reflex attempt can quickly become a chewing response, and what that means for brain and spinal cord lesion localization. We also talk about differences between client-owned and research guinea pigs, and why handling style may explain pelvic limb tactile placing changes. 

To make this useful at 2 a.m. in ER as well as in specialty practice, we walk through a guinea pig specific checklist designed to emphasize feasible, more reliable exam elements and reduce unnecessary handling. The goal is better diagnostic accuracy, faster decision-making, and improved welfare for a prey species that experiences exams differently than cats and dogs. Subscribe for more veterinary neurology conversations, share this with your zoological companion animal colleagues, and leave a rating and review wherever you listen.

JAVMA article: https://doi.org/10.2460/javma.25.12.0823

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Transcript

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Lisa Fortier 0:31

Welcome to the Epic Award-winning Veterinary Vertex Podcast, where we delve into behind-the-scenes looked with manuscript authors. I'm editor-in-chief Lisa Fortier, joined by associate editor Sarah Wright. Today we welcome Viselle Murphy to discuss species-specific neurologic examinations. Thank you for joining us, Vishelle.

Why Study Guinea Pig Neurology

SPEAKER_01 0:51

Thank you for having me.

Lisa Fortier 0:52

Michelle, what inspired you to study neurologic examinations? Full disclosure, it was my worst, by far my worst uh category in veterinary school, and then specifically in guinea pigs.

SPEAKER_01 1:05

Well, you know, I think we've been borrowing from cats and dogs for a little too long, right? In clinical practice, I think we see a range of species. And for years we've been extrapolating from the normal exam of a dog for the most part. And I think it's important to remember that animals like guinea pigs, they're the pretty common pets. And they have a pretty unique anatomy. They have unique behavior responses. And so we wanted to move away from guesswork and try to provide clinicians with a little bit more of a validated, you know, evidence-based approach to identifying first what normal is, then they can use that in their clinical practice.

Prey Species Stress Changes Exams

Sarah Wright 1:42

Yeah, I think this is going to be so helpful. Cause I know things like trying to like wheelbarrow a guinea pig sometimes are just like confusing and/or not feasible. So I think this is really important information to put out. Try to wheelbarrow a horse, Sarah. That's right. So, Michelle, what challenges do veterinarians typically face when assessing neurological function in small mammals like guinea pigs?

SPEAKER_01 2:06

You know, probably one of the biggest things we face with guinea pigs and other small mammals like that is that they're prey species, and that really does change a lot of the behaviors we see. You know, they're really good at not just hiding their disease or their illnesses, but also just the way they react to stress and the way they kind of shut down. We are so used to in cats and dogs at these, you know, looking at things like reflexes. And we we kind of expect that they're always there. But what's been really fascinating these um animals, especially guinea pigs, is that they kind of shut down all of their normal reflexes and they can override a lot of the behaviors that we would expect to see. And so it's important to kind of come at it and understand what is really normal and what is being just masked by their stress.

Lisa Fortier 2:51

So then how do you uh, before you came up with these findings, how confident do you think veterinarians could be when interpreting uh said neurologic exams in guinea pigs? Sounds pretty sketchy.

SPEAKER_01 3:03

Yeah, I think for those of us who do neurological exams in anything other than our kind of classical small animal or large animal species, it's always a little sketchy. You know, when I do exams on reptiles, when I do exams on small mammals like this, I think we always take it with a huge grain of salt. And while we were doing this project, actually, um, a group out of Germany published uh some initial data on guinea pigs as well. And that was kind of the first that anybody had even tried. And we were able to kind of take that a little bit further and compare a couple of different populations of those animals.

Lisa Fortier 3:41

So cool. Uh, and just really interesting for all the reasons that you said. And I think one of the other standout findings for me was that most tests were feasible, but when you did uh fewer of them produced expected results. And what does that tell us as examining veterinarians?

SPEAKER_01 3:56

Well, I think you know, it's first important to recognize that expected doesn't always mean normal, right? And I think expected for us was simply what the textbook definition was based on a cat or a dog. And what we found is, in fact, a lot of these quote-unquote standard reflexes that we or responses we think about just weren't there in the species. And so I think it tells us that they are just so different in the way they behave and the way that the nervous system has evolved over the years. You know, we don't have the same kind of behaviors and by extension, exam findings in these species.

Sarah Wright 4:34

I was just like a colleague yesterday when he's asking me uh an animal question. I told him, I said, Not all animals read the book. So some are different.

SPEAKER_01 4:41

Some of them just write their own book all off to the side.

Sarah Wright 4:44

Yes, yes, keeps us on our toes. So, were there any findings that surprised you the most?

SPEAKER_01 4:51

There were a few that were actually quite surprising. I think one of the ones that was really kind of weird to me was we could not do a gag reflex at all. You know, we we really tried, and a gag reflex is one of those very fundamental things that pretty much like most mammals, most bird breeds should be able to do. But we realized very quickly that, you know, their anatomy is quite different. And we see this to some extent in rabbits as well, which have been documented before. But the moment you try to put something in the back of their mouth, they just start chewing, right? And so it's just this behavior that is so hardwired to do, it completely overrides the clinical tests. And so it was a very humbling reminder to us that, you know, their biological drive to do things like chew and eat food just completely overwhelms the quote-unquote normal reflexes we were expecting to find. And so it does change how we approach interpreting, say, a brain lesion or a spinal cord lesion or things like that.

Pet Versus Lab Handling Effects

Lisa Fortier 5:46

Yeah. Another difference you noticed between uh client-owned and research guinea pigs was the difference in the tactile placing of the pelvic limbs. What might explain that?

SPEAKER_01 5:57

You know, it's a really good question. And I can't really explain why we saw in the pelvic limbs, but not the thoracic limbs. But some of this, I think, is truly coming back down to the stress levels, right? And the amount of exposure they've had to handling and the types of handling they're used to. For a lot of the pet animals, I think being picked up in some extent, even maybe a little more manhandled, is pretty common. Um, versus the lab setting, they're handled in a very specific way at certain times and they are asked to do very specific tasks. And so I think even though both these populations are used to handling, they're probably being handled in different ways. And that probably is one of the reasons why we saw in these laboratory animals, they tended to have a freeze more than the pet animals did. And that was probably what we were seeing when they did not replace their feet appropriately.

Sarah Wright 6:47

So interesting. I think it's good for people to keep in mind too, as they're working with these different populations.

SPEAKER_01 6:52

And you know, on some level too, you just from a perspective of welfare and how we handle these animals, there is a sudden level of stress inherent to any exam with any patient, but especially in these species, I think it's something we need to keep at the forefront.

Sarah Wright 7:06

Definitely. This is a little off script, but do you have any advice though to people, especially like new grads, and maybe like they're working ER and someone's brain and they're getting picked, you know, and it's midnight, they don't have any other staff there, no one else wants to touch. And I think it's not a cat or dog. Like, what should they do if they want to try to perform a neuro exam?

SPEAKER_01 7:22

My first response to that is try. Absolutely try, right? I think one of the things we try to do with this uh paper, especially, was we wanted to give people a bit of a checklist almost. We gave a list of uh neurological exam tests that we thought were fairly reliable, and we explained kind of exactly how we tested them. And so the hope is that someone could apply that in practice and say, okay, I have this checklist. This is what I can go through. And of these tests, at least maybe this is a bit more believable, and maybe I can use this in my interpretation. You know, every case is going to be a little different. And we have, I think, so far established what normal is. We still haven't done a whole lot of work into abnormal just yet. But I think if you're faced with an abnormal case, I think this gives you the framework to start with.

Sarah Wright 8:06

Nice.

SPEAKER_01 8:07

The other comment I would probably make too is just um lower your expectations a little bit too, because every animal is a little different with how they react and how they respond. And I think the reliability that we saw of even these tests that we do recommend, there's still going to be some variation there. And so being able to kind of take things slow, work with the patient is going to be really important.

Lisa Fortier 8:28

Uh you just mentioned this exam form that you developed. Tell us a little bit more because it's guinea pig specific.

SPEAKER_01 8:35

Yes, this is guinea pig specific. So we specifically went in with the idea of testing all of the things we normally test in a catheter dog, and we tried to figure out what we thought was the more reliable tests that we could find. So anything that showed a really reliable um response that was either similar to what we see in the catheter dog or if it was completely different, if it was very similar for this species, we still kind of documented that. And then we put all of that together in the list. And the hope is to give people a list of tests that they could actually use together to be able to hopefully localize lesion and work through a case.

Sarah Wright 9:12

And where can people access that template if they would like to see it and use it in their practice?

SPEAKER_01 9:17

Yeah, so it is in the paper itself. Uh so when they log in and they review the paper, it's one of the tables in our manuscript. And so hopefully that'll be useful as they go through with their clinical cases too.

Sarah Wright 9:29

So, how might this research improve outcomes for guinea pig patients in both clinical and research settings?

SPEAKER_01 9:35

Yeah, it's a really good question. You know, I think one of the things in the hospital for us is hopefully this means more accurate and faster diagnostic testing. And hopefully, by kind of trimming down that neurological exam, we're reducing the unnecessary tests and unnecessary handling of the patient. And so, from a stress level, hopefully we can minimize the stress of handling for the patient. And then similarly, you know, guinea pigs are actually a really commonly used model for a lot of different types of research, both preclinical human research or even veterinary research. And so for us to be able to interpret their behaviors, I think this hopefully gives us a little bit of context to say when you are doing research, looking at a very specific question, whatever that might be, if you're looking at some of the neurological exam tests or you're looking at some of their behaviors, hopefully this gives you some context to say, is that something that we can interpret one way or the other?

Lisa Fortier 10:30

Yeah, it congratulations again on a really meaningful study. Um, and every time we do these, it brings up more questions, more things that need to be answered. Uh so what are the next steps? Give us a glimpse into the future on areas of guinea pig neurology that still need to be explored and answered.

SPEAKER_01 10:46

No, that's a that's a great question. I think we've we've done a decent job of defining what normal is. And so now I think we need to start looking a little bit more what abnormal is. Um, guinea pigs are they're a relatively common pet, but we don't often necessarily see them, especially in the tertiary referral setting that we're in right now at UC Davis. And so for us, it's really every case we see, every case we get, we're learning something new and we're trying to, you know, expand our knowledge base. We want to now try to apply this neurological exam format to abnormal cases as well and see, you know, in combination with other diagnostics, how accurate we are with our localization. I think we have a really nice tool to start with. And then the question from here is really, you know, in the abnormal animal, how applicable some of this can be. And then I think going forward from here too, I mean, outside of guinea pigs, there's a lot of other species out there that, you know, I think also have very different behaviors and different uh ways of their quote unquote normal. And so for us to be able to establish what their normal neurological exams might look like, we've got a few different things that we're hopefully planning soon. Uh, we want to look at some reptilian species and some other small animal species as well.

Sarah Wright 12:00

Yeah, I did my fellowship at the Vancouver Aquarium. So you had 150 live-stranded harbor seals you work with often, yes. But it's often difficult to do neuro exams on them, right? It's like what even is like appropriate meditation, especially if you have an animal that is especially like free-ranging and then is trying to hide things. So yeah.

SPEAKER_01 12:17

Yeah, I mean, we were lucky at least with the guinea pigs, we could handle them. Right. Taking them forward to some of our wilder species, like, yeah, there's a lot of it that you can't really even do with hands-on exams.

Sarah Wright 12:28

Yes, yeah.

SPEAKER_01 12:29

So there's a lot of work to be done.

Sarah Wright 12:31

We're glad to have you though, uh, working on that. So if anyone's listening to this and wants to collaborate, you know who to reach out to. Absolutely. Well, Vishhal, thank you so much for joining us.

Where To Read And Closing

SPEAKER_01 12:41

Thank you very much. It's my pleasure.

Sarah Wright 12:43

And for our listeners and viewers, you can read Vishall's article on Javma. I'm Sarah here with Lisa Fordi. Be sure to tune in next week for another episode of Veterinary Vertex. And don't forget to leave us a rating and review on Apple Podcasts or wherever you listen.