Well, thanks very much for attending this webinar. What are we going to cover? Trigeminal mediated head shaking in horses.
We're gonna look at current knowledge, diagnosis and treatment options, i.e. What, who, why, and what to do about it, although I don't always know the answers to that.
This is my favourite webinar so I'd say, I hope you're enjoying my dinner. And what is trigeminal mediated head shaking is what we're gonna start with. Why do horses get it?
Who is affected? How to make a diagnosis? What can we do about it?
What to do if a client's horse starts head shaking, and how can the client help us? So that's what we're gonna cover today. What I can't though, promise is to answer all of those questions.
In fact, I can promise you that I can't answer all of those questions, but I will do my best to fill you in on what we do know. Because there is a lot we don't know yet. The other thing I'll do, obviously we are limited on time, so we'll cover the major points and obviously do ask if you'd like further information, I can bore you on head shaking for a very long time, so I promise I won't stay, but if you want to be bored further, then do you just get in touch.
So what's trigeminal mediated head shaking? It is perfectly normal, as you know, for a horse to shake its head. And there are lots of reasons why a horse will shake its head.
We all know that. But in how many horses does shaking become a problem? So we did a prevalence survey and we found it was about 4.6% of the UK equine population shook their heads so much that that was considered to be a problem by the owner.
How many of those head shake due to a trigeminal neuropathy? Probably 90%, but that's out of horses that are referred to a hospital for investigation. So there are fewer in the population, and it is therefore important to consider all possible diagnoses, so.
The reports that head shakes so much that there's a problem, 90% that come to a hospital will go home with a diagnosis of trigeminal mediated head shaking. However, you will be finding far more that never come to a hospital because you get the answer at home. So, although the owner might perhaps jump to trigeminal mediated head shaking, do make sure you consider everything else as well.
What are the clinical signs of trigeminal mediated head shaking? Well, these are actually really quite important because they're quite key, as a, as a stage of our diagnosis. So the signs are usually pretty classic.
So they have predominantly vertical head shaking with some sharp vertical twitches and flicks. It's accompanied by signs of nasal irritation. They snort, they sneeze, they might twitch their lips, they might rub their nose, they might strike up at those with their front legs, and it is both sides.
It's worse at exercise and crucially, any exercise. They'll be ridden on the lunge, you could loose school them, you can ride and lead, whatever. It's not a rider thing.
Why having a saddle on thing. It is any exercise. They can also be affected at rest, although again, they are usually worse at exercise with trigeminal mediated head shaking.
It is actually very, problematic if they're affected at, at, at rest from a welfare point of view, but, we'll come on to that later. Some of these horses are seasonally affected, and, and you know that, don't you, that they seem to be, you know, come come the spring. It's when we see the head shakers.
How many horses are seasonally affected or what proportion? Well, 25. To 64%.
Now, why the massive range? That's because it depends on the question that was asked. So, the, 25% is, is my figure, and that was the question is, is your horse completely better, out of season, which is normally in the winter.
And 64% is if you say are they improved. So we're seeing horses that may well improve out of season, but actually only a quarter of them are free of clinical signs. Anecdotally, some are only affected when exercised outdoors, not indoors, and some are worse at hacking or near trees, and that will vary, on an individual basis.
So here's this guy showing the really classic, trigeminal mediated head shaker sign. So the vertical shaking, he's snorting. I've, I've got the sound off, but, I think you can see his nostrils go.
He's licking his lips. He's got some sharp vertical twitches in there as well. And he is not a happy chap.
And one thing I actually find really useful is to show these videos to clients, because especially if their horse isn't a trigeminal mediated head shaker but they think it is because they read it on the internet and they joined a group, . They'll watch the video and, and they fall very much into two camps. So, oh, yeah, yeah, that's what Benji does.
Or, oh, no, no, Benji does something different. And, and they'll really, it's quite obvious then, actually, whether their horse has got classic signs or not, because they could see the video and compare it to their own horse. So another one showing pretty classic signs, this one on a Welsh hillside, however, we're doing the same thing.
And they seem to show signs worse in trot than canter, don't they, which is another trigeminal mediated head shaker thing. I think that's potentially just biomechanical. And then this one out hacking.
I think the rider was quite bold. You'll advisedly say, potentially. So these are our classic signs of exercise, and then if they really severely affect, you'll see, see this at rest.
This mare's a very good show jumper, well she was, was even worse if she came out of a stable. I mean, you could barely move her out. She was hysterical.
But it is important to, to differentiate that from a horse that does this in a stable, but not out of exercise. But again, it's very easy to differentiate with just getting a history and watching the horse in some videos. So think hard if they don't show classic signs.
Now this one does show vertical head shaking. She doesn't show any nasal irritation, there's no snorting, no sneezing. And she didn't have any of the sharp, vertical movements either.
I'll see if I can play that again for you. But she certainly at this stage could could well be a trigeminal mediated head shake, and she's certainly got vertical head shaking. However, on the lunch, she is absolutely fine.
Now, it's not a rider problem in this case. Actually, she's ridden very, very nicely by a, professional event rider who was actually very sympathetic and quiet rider. So, where are we?
It's actually just, an issue of rider weight. Now, the rider was for sure not too heavy. So where do we go after that?
Well, this is where it's great being a medic, because I just called on orthopaedics. And they came and actually, and then I think you can see that as she trots around on the lunge, that her hind limb movement for a. Sort of smart horse is not really what you'd expect.
Probably that those of you who do lamenesses would sit there saying, well, she looks lame. But, I think she just doesn't look quite what you'd expect, but that they found sacro reac disease, and she actually responded very well to treatment, with steroids, around the sickpririliac. And what about this guy, vertical head shaking.
Rubs? Licks his lips, off he goes again, sharp jerks. But what do we notice about him?
So he's doing it in the stable. He's actually worse in the stable than at exercise, but potentially, that's because he has something to rub on. He was certainly not normal at exercise.
He wasn't a happy chap. He's presumably showing signs of neuropathic pain in that, well, that's what we think trigeminal mediated head shakers are suffering from, and people with neuropathic pain get pins and needles burning. Electric shock-like sensations.
Whereas if, you know, if you've got normal dental disease, if you like, you, you actually, they'll eat incredibly well considering how bad their teeth can be, but they'll, they'll quid, won't they? So I think he's still showing neuropathic pain, but is he a trigeminal mediated head shaker? Well, if we watch his video again, what do we notice?
He has rubbed that left side raw. And he only rubs the left side, so he's one-sided. So immediately, I think, well, we might well be dealing with neuropathic pain from the trigeminal nerve, but there will be a pathological, cause for that.
We'll see gross pathology. I'm sure there's a pathological cause for trigeminal mediated headshaking. We just don't know what it is yet, but, we'll, we'll, we'll find gross pathology on that left side, which is exactly what we did.
So he had, A T3 abscess that had eroded the infraorbital canal, leaving a naked infraorbital nerve that was then giving him neuropathic pain. So, I always think if not classic. So we've mentioned this a little bit already.
Well, what do we know about trigeminal mediated head shaking? There's a, an, a quite a nice anatomical slide just to remind us of where our, our trigeminal nerve goes. What do we know?
So, this nerve has become sensitised. Well, actually, the infraorbital nerve, that's the only one that's been tested. The initial branch, has become sensitised, and it fires at a threshold that's 10 times lower than in a normal horse.
And we think that is what's causing neuropathic pain. Obviously, we don't know because we can't ask these horses what they experience. But neuropathic pain in people, pins and needles all the way up to burning an electric shock like pain.
And having, had my leg broken by a young horse, riding it, not treating it. The, and, and I've experienced really bad neuropathic pain for a year, and I, I can assure you it is a markedly unpleasant sensation. Excuse But in these horses, we've got this sensitization, but there is no physical damage to the nerves, if you look at this nerves down a microscope.
It looks perfectly normal. That's a, it's a really dull project. Just if anyone's thinking of doing a project, try and find something more interesting than that.
The nerve's really long. So I based it on some stuff that was done in people, and they had their nerves are quite short. The horse infraorbital nerve is really long.
And then you have to look at all these slides, cut at microns, you know, all the way down the nerve. You have to look at these with a pathologist and admire what they're doing. Cause actually, I didn't know.
I just had to, it's very. Watching your husband mend the car, isn't you just want them to mend it, but they want you to come and say how amazing they are for having done it. So I had to look down the microscope with them and go, Gosh, that is normal, isn't it?
Wow. For about 3 days, and it was dreadful. So don't do that project.
But we did find that there was no physical damage to the nerve. And that's quite good because presumably, we've got a switch that's been flicked to make this nerve more sensitive. And maybe that means we can flick the switch back.
Trouble is we don't know which switch and we don't know what's flicked it. I do have some theories but I won't bore you with those here. So it can be reversible very possibly, and that's actually supported by seasonality, and a 5% spontaneous remission rate overall as well.
So, actually, that's maybe it's maybe a good thing, isn't it? You know, if we did find a massive amount of demyelination to the orbital nerve, I mean, in some ways, it'd be better cause you could just say there's nothing we can do. Sorry.
But it's a bit hopeless, whereas this way around, well, yeah, maybe there is something we can do. But we, we don't quite know what yet. So what we don't know, we don't know why, we don't know how, we don't know who.
We don't know what what the switch is, how it's flicked, why it's flicked, how do you flick it back. Are all horses sensitised? So that study is just based on a 6 or 7 horses.
And there is more data from Hanover, taken on clinical cases that perhaps shows that not all horses are sensitised, but there's quite a lot of, It challenges to that, to that work. It's very good work, but using clinical cases, you know, and, and you've got a, a condition where we don't have a, a diagnostic test for it. Why just that nerve?
Most peripheral axonopathies in people affect more than one nerve. So in these horses, is it just the infraorbital branch? Is that the rest of the trigeminal nerve?
We don't know. I did, again, I do have some theories as to why just that nerve, but, I won't bore you with those. There is a very complex environmental interaction, and we know that, don't we?
We'll get horses that only do it near oilseed rate. There's actually often a, a history of a recent, environmental change. They've moved house and obviously the suspicion is that people got sold a head shaker, but I don't know that that is really the case, in a lot of situations.
I think that's part of, of, of how the condition comes along. So there is something to do with the environment. It's not allergy.
If you treat the horses with steroid, they know better. But there is something, that potentially then working on, on, on mRNA expression, something like that. I don't know, but there is something going on.
And again, I can bore you for longer. But it's all, theories, there's nothing proven. So there's a load more work to be done, and I very much hope that, you know, in sort of 1020 years' time, that that that a webinar like this will have a lot more information in it.
So who's affected? Well, it definitely happens worldwide in developed countries. It doesn't seem to be something that's reported in developing countries, but that could be.
That, you know, particularly a working horse population, they may be exercising at lower levels of intensity. They, the, the, the focus is not on, on that. I'm not sure.
4.6% of the UK equine population are judged by their owners to shake too much, so much that it's a problem, although actually only 1%, went on to call a vet about it, and a lot of them treated it without veterinary intervention. It appears to be acquired, as a young adult, so the median age of onset is 6, but there is a wide range.
And I do have one of, he started head shaking at 17 and had been in the owner's possession for many, many years. So that was definitely a real one. But, I was contacted last week about a 20 plus year old stallion who'd just started, and I was like, really, we're gonna find something else on that one, which is in fact the case.
It appears to be any breed and any use. There is no evidence of direct heritability. There are no specific studies and I don't think if you.
Breed to head shakers, you make a head shaker, but there must be some genetic involvement somewhere, as there is in so many conditions, that when it, you know, meets with the right environment, it sort of creates the perfect storm. So there must be something, but we don't know what that is. And I think if you've got a head shaker that's not affected at rest, I, I don't know that you would be at any increased risk taking a fall from that one.
So there's a lot lot more work to do here I say including considering the unknown environmental interaction. So how do we make a diagnosis? So it's currently is a diagnosis of exclusion and that means we are likely to over diagnose.
Now, if I look at Jeff and Tim's work back from '87, so 98% of cases presenting to a hospital for head shaking went home with a diagnosis at the time of idiopathic head shaking, but what we would now call trigeminal mediated. If I look at my own cases, but I haven't published it, so that's, Definitely not, not been through peer review. Unpublished hand tally at Bristol was 90%.
So we do have better diagnostics now. I certainly not uncommonly find things on CT that I say, oh, you know, 10 years ago, or perhaps more than that now, when I didn't have CT and I radiographed them, I would have made the wrong diagnosis. But it is still only exclusion.
We have, published some work on the number of times we find problems on CT, and again, Hanover are looking at the number of times they find problems on MRI because they do that routinely. So I think that there are, there is a way to go. Is there a role for finding out the somatosensory rate potentials, that's the test they did to see if the nerve is sensitised.
Could you do that to prove whether or not your horse is trigeminal mediated? I. There may be a role for it.
I think we don't know yet whether it's every horse that's, affected and actually potentially it really isn't. And all it would tell you is that the nerve is sensitised and not, not perhaps why. So there may be a role for it as part of a full investigation, but, I don't think we're gonna be able to, you know, run a test for trigeminal mediated head shaking just yet.
Although, again, I do have a few ideas there. Is it worth making a diagnosis, if the client thinks the horse is a trigeminal mediated head shaker, are they better to spend their money on treatment than on diagnostics to tell them what they know already? So I push for diagnostics because, so almost any diagnosis is better.
So take the 10% chance of finding something else. And this is a hospital population, so there must be more horses with another diagnosis out in general practise. There's a massive increase in awareness of the condition amongst owners, which is really good.
So, not so long ago, you know, it was a behavioural thing. Maybe it was allergy. You know, I graduated in 2003, and that's sort of what I was taught.
And I struggled when, I worked in, in. To, to have things, you know, the the these cases put through on insurance until I did a nerve block actually, and then showed that it was pain related. But they were very much, it's just behaviour, it's just behavioural.
And I think we've seen that change in, in UK insurers as well, that they used to say, if you don't get a diagnosis, then it's behavioural and we won't, and we won't pay. And I think we're perhaps better at making a diagnosis when we. No, because we, we know that, you know, it's a diagnosis of exclusion.
We expect to find nothing, but we do expect to find classic clinical signs. So I think that we have got a risk of owner-led over diagnosis, and we know we may over diagnose as well. So I do think it is worth running the tests to be as sure as we can.
How to make a diagnosis, so I think history and observation is the most important. You, you'll really get a really good idea as to whether or not, neuro neuropathy is likely. And as I say, think very, very hard if they're not classic.
It doesn't mean you won't end up making that diagnosis. So I've certainly done it on several occasions and gone, I, this is the best I can come up with as a diagnosis, but, it's some sort of variant or I'm missing something. So history and clinical signs.
You want to be about the right age. Usually sudden onset, not always, and you've just got this really classic head shape movement. I like to find out when shaking occurs.
So is it worse out at exercise? Is it ridden? Is it on the lunge, is it more hacking?
Just to find out more about that. What's the character of shaking, so up and down, side to side, round and round. Sometimes it's useful to know before I see them, whether they've responded to abu trial or corticosteroids.
Trigeminal mediated head shaker won't do. So those, those trials are quite useful to have on board. We can always do them later as well.
So you, you judge it on a case by case basis, but, certainly not wrong to try those. And in response to a nose net, now. A nas net will improve 25% of trigeminal mediated head shakers by up to 70%.
So if it, the horse responds to a nose net, that may well fit with being a trigeminal mediated head shaker, but obviously a lack of response doesn't get us further forward. You've also got the, the subset of horses that's 70% better is not enough. So if you're a good dressage horse, 70% better.
If you're a moderate head shaker, even it's not enough, possibly even a mild head shaker. I think placebo is always a problem looking at treatments for head shaking and, and trying to tease that apart. You know, if you go to any competition, someone will have a nose net on, but, why?
So, yeah, try and read a, a, try and make as, as objective a study as possible. I am actually working on an objective measure for head shaking at the moment. So I grade the, the horses, which is, is not necessary really.
I just found it was useful, to try and make, your sort of outcomes assessment more objective. And I made up the grading system, so I'm happy to take any any criticism on it at all. 0 out of 3 for no head shaking.
1 out of 3 head shaking exercise, but not sufficient as to interfere with ridden exercise. 2 out of 3, head shaking exercise, making the whole. Impossible or dangerous to ride.
And then 3 out of 3 is head shaking even at rest. And, and then that's particularly relevant for horses that may be covered by, you know, mortality insurance under beaver guidelines that, a 3 out of 3 horse will not be able to, to live a, an acceptable life, retired from work. So the next stage, sometimes I do, sometimes I don't, is the head shaking due to facial pain.
So, what are we blocking? We are probably just doing a maxillary nerve block. I've published quite a bit in this area and, I think we, we were hoping we were more specific, but.
Are. We're just doing a maxillary nerve block. The best place to do it is, you know, we'll see right at the, at the back, under the zygomatic arch, rather than over near the, the infraorbital foramen, because you're only blocking a tiny bit of the infraorbital nerve.
And then when, when do we block? So a positive result will confirm facial pain, but not, I can tell you why. So, it's not a test for trigeminal mediated head shaking.
It's a test for face pain. But a negative result won't rule it out, and there's lots of reasons why nerve blocks don't work. Probably the most important one for this test is just being in the wrong place and.
We did a, a CT, study on that, and that showed, really, if you're not very experienced, then you're in the right place only 5 to 20% of the time. And that's obviously just using contrast. And we do put in quite a lot of local anaesthetic, although I don't try not to flood the whole head.
So I, I put in about 10 mLs. But the, sort of 2% of the pivocaine. But, but the maxillary blocks, people will use more.
But, Yeah, I think we're not that great at hitting the right place. It can be easier, if you do the ultrasound guided. I guess I don't, and that may be something that I change, but, I tend to find I have these horses very, very, very lightly sedated, because just like a, a lameness, you know, you can't have them really asleep, and then block them and then exercise them, because you've got that confounding factor and, and safety, obviously.
And I do find that I, I struggle when I've got the ultrasound probe and the needle and a very awake course. I struggle to get it all in, whereas I'm just sort of quicker to pop the needle in, but that's, that may be wrong. I'm certainly open to to changing.
Now our recent work showed that where you were confident in your diagnosis of trigeminal mediated head shaking, response to nerve block didn't predict treatment outcome. So When do I block? You need a horse where the head shaking is consistent.
It's moderate or severe. I think it's could be bad enough that you can clearly see a difference. They're affected at exercise mostly because that's then, it's a sort of reliable, reproducible trigger for the head shaking that you can do the exercise and then do the nerve block and then do the exercise again.
There are questions as to a diagnosis of trigeminal mediated head shaking, so I think if you've got a horse that's completely classic. I don't really know this is gonna change anything, because if you do the test and it, it supports your diagnosis, and you go, oh yes, he has got face pain, lovely. But if it says he hasn't got face pain, you don't believe it anyway, so it doesn't change what you do.
And I think everyone needs to be aware of those limitations before you start. Unaware of the risks, and there are risks to doing this nerve block. I always cause minor side effects.
I've never caused a major side effect, but that is, only a matter of time, isn't it? So, I think everyone needs to be aware. Now the last time we did this block was on a mare who looked like a classic head shaker, but was very for limb lame, I mean, markedly for limb lame, which was not perceived by the owner to be a problem, potentially because that for limb wasn't insured anymore.
And, and that was a difficult one, because I thought like, I can't ignore the fact that maybe she's shaking because of her for limb lameness. You know, yes, she looked neuropathic, but you know, maybe this for limb lameness is even cervical spine in origin. And maybe that's going on.
So we, we weren't allowed to block the for limb lameness. So, so we blocked the head, and she stopped head shaking, at exercise, but remained markedly fallli lame. And, and to be fair to the owners, they did only want her to be, happy at, at, you know, retired, which she, she had to rest.
So, I think, or at least in sort of gentle paddock wondering, she was head shaking. So, I think we weren't, we weren't wrong to do that, but, you know, you always worry about people ignoring us as severeians, but they, they did just want to retire her happy. So this is doing the nerve block, say, using a very, tiny little bit of xylazine.
I have got a bit of local under the skin there, and obviously then there's quite a big spinal needle. And I think that's where I get stuck with my ultrasound probe, and there's sort of too much stuff near its eye, especially if you're trying to line, line, line things up. But maybe that's just because I don't do, do enough of them, not for head shaking.
You know, I think maybe people who, who used to using the probes for dentistry would find that easier. So this is one, again, very classic, head shaking, you're getting used to seeing this is what they do, pretty much all of them. Around the gay.
And then after a nerve block. He stops head shaking. So we quite satisfactorily proved that this horse head shook due to face pain.
So we don't always get such a nice answer. And, and as I've sort of evolved through my, publishing in this area, I probably do it less and less. I certainly started off saying every horse should have one done.
And I have changed my, my mind on that, and I think now you case select. So where do we go now, further diagnostics. So head shaking due to face pain is proved or suspected.
So the next stage is, is there any gross pathology which could be a cause for face pain? And it may be that you need to treat abnormalities and see if head shaking resolves, and if it doesn't make a diagnosis of trijaminal mediated head shaking, bearing in mind the limitations of that. So we do a clinical exam, and from that findings may lead to further tests, upper respiratory tract and guttural pouch endoscopy, ophthalmic exam, oral exam, CT scan, and we do take blood and urine, but I have a little bit of a lack of knowledge how to interpret the results before they've been quite normal.
But that isn't the case all over the world. So, eye specialist looking at eyes for us and dental clever people looking at mouth for us with oroscopy, and a CT scan. So just a little case here, this was, a mare she presented with a gradual onset of head shaking at the age of 14.
It was vertical head shaking, no nasal irritation, and it started about 20 minutes into exercise. The owners didn't lunch her, so the owners didn't know if it happened on the lunge as well as when it was written. I watched some videos, and yeah, vertical head shaking.
We lunged her in the hospital, but no head shaking. Now, that, no, that's not uncommon, is it? That they, they don't always, head shake to start with a new environment.
That they will change if you keep them in for a while. So it certainly could be trigeminal mediated, but no nasal irritation. Gradual onset is possible, but it is less common than acute.
14 is a bit old, but not impossible. And she had possibly responded to Butte, but they weren't very sure. And actually, when they looked back at it, they did the classic Butte trial thing of, we put her on Butte for 2 weeks, but we only rode her once, and she didn't head shake on that one ride.
But then sometimes she doesn't anyway. So, probably needed to try that again. So she could still be trigeminal mediated, but I certainly had some questions there.
Now, I couldn't do the nerve block because, I wasn't really in a position to do the nerve block and send her off on a, on a hag, given, that they'd have had to go down the A38. So, we, we decided to proceed with the CT. And when I was sort of saying, Well, she could be, she might not be, the owner said that they bought her, 4 years ago, and she was passported as a 10 year old at the time, but she'd only got given her passport two weeks prior to purchase.
So they did think maybe she'd been Possibly a little older than she was passported. Oral exams suggested she was 18 plus, probably 20, and CT found very little. She's got tiny, tiny teeth, hasn't she?
Very little reserved crown. And obviously, different horses age at, at different speeds in the dental department as, as well as everywhere else. But, I mean, that is, they are markedly tiny teeth.
So I do think she was probably really more like 20, which then makes trigeminal mediated head shaking much less likely. What we did find, however, was marked temporohyoid osteoarthropathy. I thought, oh, now that might well be a thing.
So we discussed what to do and we thought, well, we obviously have this question that maybe bee has helped. So we said, well, let's do a real proper but trial and then let's, if that. Works.
Let's see if we can manage her on bee. Otherwise, let's, potentially have to look at surgery. But she actually responds extremely well to Bute, once that was, she was exercised regularly and, and the beat was on board.
So she's done, done really well. But definitely worth going looking. However, most trigeminal mediated head shakers are harder to treat than a head shaker with an osteoarthropoy that responds to beat, so.
It's not easy to manage trigeminal mediated head shaking, but you know that. Why? Well, neuropathic pain, neuropathic pain in people is very difficult to manage.
The best treatment, and, I can, you know, put my own experience into that. The best treatment for neuropathic pain in people is cognitive behavioural therapy, so you learn to deal better with your pain, which trust me, is really rubbish. I mean, it's quite a good system, but, I mean, you know, you, you don't, you want to take two painkillers and get better.
You don't want to be told, Oh, let's learn how to cope better. We don't understand how the nerve is sensitised. We don't understand where that fits in trigeminal mediated head shaking, and I think we may well have more than one cause with the same clinical manifestation.
And even with the same signs, individuals are gonna vary on what helps them. And that's also the case in people, as I suspect we will never find a one size fits all treatment. And possibly not a one size fits all Etiopathogenesis either.
So I'm just gonna go through the treatments with some proven efficacy, and that's published, so, we won't cover lots of the things that people do do. Any proven head shaking treatment does seem to work by reducing sensory input from the trigeminal nerve even before sensitization was known to occur. So the nose nets, we've mentioned this already, up to 70% relief in 25% of cases.
It's the first treatment to try. It's cheap, it's non-invasive, it's risk free, you can compete at most levels in most competition disciplines, although by, certainly not all. But you know, you can put one on there about 12 pounds and try it out.
How does it work? The mechanism is thought to be similar to, to gait control theory. Or it is gait control theory, probably that's a little bit of a debate there that we won't go into.
But basically the same reason why you bang your elbow, you rub it and it feels better. And it's to do with, the gate in the spinal cord to allow, sort of low level, touch, and touch sensation to go through, which then blocks the gate for the, the pain C fibre to go through. So here is one, not a very bad head shaker, but a, a head shaker.
Certainly can't do her intended job. Which is a bit of pony club camp and that kind of thing. Nothing too, exciting, but, a fun, a fun pony.
The, orthopaedic people amongst you will be looking at her behind them, as I expect, but we'll move on from that. So there she is, head shaking some. And here she is with a knas net on.
And she's head shaking a lot less. She does a little bow up this side. There we go, and apart from that.
You know, she's certainly fine to go off and do her job now I think both from a performance and a and a welfare point of view. Now, having said I was only gonna look at the published stuff. I'm now gonna mention the face mask, which isn't published, which is a bit naughty of me, really.
But it sort of makes sense to bring it on from the nose net. So, potentially if you cover the eyes that can reduce stimulation of the ophthalmic branch. And, and some people find that happens, that's all you need to do, although I do think that is quite a small number of horses that are afraid to, sort of phobic, .
I it's difficult that I'll be dealing with something else there. The Guardian mask is the best one for getting rid of UV lights, so let's try a Guardian mask. If an eye mask alone is effective, you can actually try tinted contact lenses, but that's like a top competition horse type of job.
In my experience, rarely enough on its own, but sometimes a full face mask, added, you know, to, to the nose and the eyes makes the difference. And, and that's where we are if we go back to our little man. Now she's got eyes and nose covered, and you've just got that extra.
Response from her, from her clinical signs. This guy's a top competition horse territory, can compete within the UK, with a face mask on, and, and actually we didn't get on with contact lenses for him going internationally, but we did try, because tinted contact lenses could be, the way forward. What about pharmaceuticals, so what's published, ciproheptadine and or carbamazepine and then gabapentin is published for neuropathic pain in the horse, but not for head shaking.
Now, in people with neuropathic pain, the drugs have got inconsistent results, and you'll have a lot of variation between individuals, even with the same sort of signalment. I don't know you are signalment probably, and, and, and, and, disease. Results can be short-lived, but response to medication can aid diagnosis, even if results are short-lived.
And some people will have side effects such as drowsiness, although actually those can wear off with a bit of time. Now, in the trigeminal mediated head shakers, the drugs have inconsistent results, or they've not been published. Results may be short term.
We don't know how many tablets to give a horse, and we just go, oh, a horse is 7 people, and then there's some tablets left in the bottom of the tub, so we're chucking them in as well. We really don't know what we're doing from a pharmacology point of view. So I think we're going to have less good results as people.
And certainly the, the recent debate on, how much gabapentin to get from a, a bioavailability point of view is, is the perfect example there. Some horses may be affected by drowsiness, so are they safe to ride or safe to handle, but some individuals can respond well. So, I did two week trials, but inappropriate cases, you can't compete.
So if you've got a horse whose, desired role is just to compete, there really is absolutely no point, in, in having them on the, the, the tablets if that's their only future. But if they are appropriate to try, then I do do these. I tend to do them later, after neuromodulation, which will come onto in these horses that haven't responded.
But I start on a high dose and drop down, warn them about safety so they may not be safe to ride or handle if they are sleepy. So I think that's important. But if they do stop head shaking on a high dose, then you drop the dose down and find is the lowest dose one that is affordable and one that means the horse can be ridden.
So that's how it, it's actually cheaper to start high and drop down and start low and climb up. So although you, you sort of day one is really expensive, I think that's actually overall a cheaper way of doing it. But I can always help out with doses if people want.
So what else is published? So supplementing oral magnesium and boron. This was work done from Davis and this reduced head shaking.
Now these horses were still head shaking. But, but they were better. And, and that's good.
Feeding concentrate has an effect as well. Most of our horses do have access to concentrate, but if you don't, and that these horses to start with were just on, on hay, and then when they have a bit of concentrate. They added they did a head shake a little bit less.
So, should we supplement magnesium in these horses? Yes, I think so. What I wouldn't expect is that a little bit of powder on the food is going to create a cure, much as owners would like it to.
So in the US, there's a platinum performance supplement that has that mix. In the UK we actually sort of working to try and make something a bit better, but boron is not allowed as a feedstuff in the UK or the EU. And the boron is only there to make the magnesium easier to absorb.
So, it just makes them more magnesium. We are measuring magnesium levels and urine pH in our cases, and so far they seem pretty normal actually, so we may just be dealing with a slightly different population. Are we treating cause or effect?
Probably effect, I think, with the magnesium. With the way it can, it can work on, receptors, which I can again for you about separately should you want. And there is a bit of work happening on changing diet, but there's not many outcomes yet.
Surgery, so, it's the question that a lot of clients ask, but if it's the nerve, can we just cut it? Well, Tim's work was important. He cut the nerve, and actually, 3 horses out of 19 got better.
And that was important because it said, look, people, this is a nerve problem wherein everyone had been chasing down allergy and all kinds of roots. So, really important, but obviously, we do try and avoid neurectomies, particularly actually in this nerve, which, which loves to form a neuroma. And these horses did self-traumatize.
So, It, it was useful as part of the picture. When I did my residency in Liverpool, we tried to make that work better, but sort of as a spin-off on some stuff that's done in people, and we put coils into the nerve to try and scar it without cutting it. And actually some of these horses did do quite well, but.
This is the problem is, is the side effects of nose rubbing, and although it's mostly short term, it's markedly unpleasant and in 4 out of 58 horses, it resulted in in euthanasia. So now we have something better. I don't do this.
And, and I think that's just part of the evolution, isn't it, of us trying to find the right way to treat them. So what do we have that's better? Neuromodulation.
Now, how did we come up with that? We have an established collaboration with Southmead Hospital and through the Medical Sciences at university. And there are lots of possible treatments for people with similar neuropathic pain syndromes and no one.
Good solution. But the percutaneous electrical nerve stimulation, is a minimally invasive technique, can be used under NICE guidelines for management of neuropathic pain in people. There are a few blinded trials, but not really any, significant amount of basic science.
We, what do we do? They place an electrically conductive probe over the offending nerve and stimulate it at various frequencies and voltages, based on a human algorithm for a set period of time. And they say anecdotally, probably, try 3 treatments before you say it doesn't work.
Importantly, people say once the probe's in place, the procedure's quite pleasant, and there are no reported side effects other than a bruise at the site of the probe insertion. So we thought we'd have a go and see if we could do this in these horses. This is Dude, one of my favourite horses ever.
And here we are, doing it. So that, it changes, frequency, and so they twitch every 3 seconds, and then people twitch, and then they experience a tingle. So presumably these guys get a, a tingling feeling.
So we, we showed you could do it standing, sedated and actually dude is still, free of head shaking many years down the line. So it was safe. You could do understanding sedation, and we got 5 of 7, horses back to ridden work, but we obviously had very short follow-up times, and I think it is unrealistic to expect us, this is a management technique, and people, you know, it's unrealistic to expect cures in horses.
We looked at 168 horses then when we, launched this then as we pens and we, we treated 168 horses across the UK and Europe. And they all did the same equipment and technique, and that was 530 procedures. We got complications in 8, all of which were transient except one which is, I think we're on the fence as to whether that was a complication or natural disease progression.
What is, and we were quite fussy about complication. You know, I've, I've got catheter complications and dermatitis and, one got a mild episode of medical colic. So, which one matters?
Well, 3.4% got a suspected neuritis, which was, which is nerve inflammation, obviously, evidenced by a worsening of signs that lasted a few days. So we could speed the recovery if we gave steroid.
And we found if they had neuritis once they tended to have it again at the next procedure, so we would suggest pre-treating with steroids the next time, but these horses weren't too bad. We also showed you should do 3 procedures. Now if you've got no remission after 3, you can do more, but with reducing odds of success.
After 3 procedures, we had 53% remission. So half of these horses, you're gonna spend all your time and money doing this procedure or 3 times and then go, Oh, that was a waste of time. Hopefully you won't regret it, other than time and money and breaking owner's hearts.
We're not gonna say, oh gosh, I wish we'd never done that to this horse. But, but half the time it's gonna be pointless. The other half of the time, it's gonna put them into remission, which was judged as returning to written work at the previous level.
And from 2 days, which is clearly pointless, and 2 years ongoing, within an average of 9.5 weeks. And, and I think that average was really unfair.
So half the courses were still in remission at the time of follow-up, and I think We have no predictors. We can't tell whether the horse is gonna be one that is in remission at all. And if it goes into remission, whether that's gonna be 1 week, 10 weeks, or, or, or 9 months.
Your average of 9.5 weeks is anything between 2 days and 5.5 years at the time.
So, I think it really is a case of, of suck it and see. And this chart shows that. So if you look for in the middle line.
You can see that that that's how the number of horses that go into remission is about 5, and then as the line drops, that's horses going back, to head shaking. And it does look like if you don't head shake for a year, that you are then cured, and that's 18%. But I do think I just need to go into this expecting this to be a management technique and not a cure, because, that, that would just be too good, wouldn't it?
So if you relapse after 3, you usually go into remission after a 4th, and usually for longer, but not always, there is a little drop off. And that, that happens as, as, as we carry on. There are no predictors.
So I think it's very difficult, you know, if you already own a head shaker, this may be the best way of managing them as you do your 3 procedures, they go into remission and then you do. A top up as and when required, but, I know I wouldn't really want to buy one, that I knew had responded to three procedures because I wouldn't necessarily know it would respond to a 4th. So I think at least until we know what causes trigeminal mediated head shaking, we're gonna struggle to treat it, and we don't know how neuromodulation works, which makes proving it, improving it difficult, but I, I do think it's the safest procedure with the best results available at the moment for horses where a nas net doesn't work, and so I do hope that that changes.
Electroacupuncture, also provides percutaneous stimulation of the nerve. And was used in 6 horses as an additional treatment along with face masks and nose nets and got a median remission time of 2.5 weeks.
And really what we need to do with the electroacupuncture is get more data and see is it comparable to depends or is it, not quite so good, and we don't have that increased data at present. So what do you do if a client's horse starts head shaking, so the first thing is advise them to stay safe. I think if the horse is distressed at rest, then you do need to see it quickly, but otherwise, I think there are benefits to getting the owner to observe, record, and video first.
Otherwise, you go out and see it and the horse isn't head shaking and horse looks OK, and you know, what what do you do? So getting some videos is really helpful. But then, examine the horse.
And, you know, after examination, it depends on the case, I think you might want to do some all or none. Of, of supplement magnesium. I advise owners to try three types of no nets.
So there's a sort of competition legal one. Then there's one that's almost like a nose bag, and then there are ones that are like a sort of shield over the nose at the front, like a hard shield. So there's like a million different front nose nets on the market, but they do tend to fall into those three categories.
So. Try 3 types, and they can usually get hold of them secondhand or, dare I say it, off an internet forum, someone will lend them one. Try a face mask in the Guardian one is best for UV and potentially abutril or inhaled steroid.
And obviously, if you don't think it's trigeminal mediated, you're gonna try something else. But those are just a few, a few possible things to do depending on the case. It can come and see us, and we aim to see them in what is quite a full day.
And one of the advantages of being in a hospital is that if it looks, perhaps that there's an orthopaedic involvement, then, and or dental, you know, we've got, got the right people in the right place to, to see them alongside me. How can the client help, say, participate in clinical research? And mostly that involves allowing us to ask lots of questions about their horse, and their signs, and giving us access to the horse's case notes for research, and allowing us to contact them for follow-up.
And some trials, like the one I'm running at the moment, where we will ask for specific consent as well. So they're not gonna be doing anything that they don't know they are doing. They can also, support, support us financially through the Lang Trust for Animal Health and Welfare.
They have a, a noddy Neddy's Facebook page, and there are links for that on the BMW website, but that supports, head shaking research directly. So in summary, be as sure as possible of a diagnosis. Make sure they're on concentrate, give them magnesium.
Try nose net. Try a face mask. Try equen neuromodulation.
If that doesn't work, try drug trials. After that, there isn't really anywhere we can go. People will try lots of stuff that's not published on their horse and maybe they'll find something that works, but, I think we, you know, we need to be cautious of encouraging people to try lots of different things and in the meantime, the horse is, is suffering, so.
Not always a happy outcome for these cases, because we need to know more about the disease to move forwards. So just to finish up with a nice case, this is a very bad head shaker. His friends really care and they just, you know.
And here he is after his neuromodulation, and he's, he's been fine for years now. And these are our contact details. So that's it.
Thank you very much for attending, and then. I'm sure there'll be a way for you to ask questions.
