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Stringhalt
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Max
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 Posted: Thu Aug 30th, 2007 02:36 am
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Is stringhalt conformational or is it a sickness? I have been told two different things so am confused!

DrDeb
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 Posted: Thu Aug 30th, 2007 06:43 am
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Max, Stringhalt is a disease. The word comes from German -- "string" like the strings on a marionette puppet, and "halt" meaning lame -- so literal translation, "the disease that makes him lame in a manner as if someone were operating the hind legs from above like a marionette".

There are two known causes for this condition, and they may, in fact, be related. First cause is mechanical -- having to do with the tensional co-adjustment of the long tendons investing the hind limb. Second cause is the ingestion of substances that attack the nervous system that operates the hindlimb machinery. Research in both Australia and the U.S. has fingered the plant genus Hypochoeris, otherwise known as "Cat's Ear", a plant that commonly grows in pasture and is also called "False Dandelion" because it grows from a basal rosette and has yellow flowers, like dandelion.

When the new Poison Plant book comes out that I am hard at work on, you'll be able to read all about it in there. You can also read about it in Knight and Walter's "A Guide to Plant Poisoning of Animals in North America", or in the Australian "Plants Poisonous to Horses", available from the RIRDC department of the Australian government.

For more on stringhalt, see back issues of Equus Magazine. -- Dr. Deb

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 Posted: Fri Aug 31st, 2007 05:25 am
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Thank you Dr Deb.

Jeannie
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 Posted: Thu Jan 31st, 2019 02:47 pm
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Dr Deb, I am going to be working with a horse with mechanical stringhalt at the walk in one rear leg from an old injury. She can trot and canter. I would like to do lateral work with her, and wanted to know if you had any advice about how the stringhalt would affect her ability to do collected work on the ground and ridden.

Jeannie

DrDeb
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 Posted: Thu Jan 31st, 2019 11:33 pm
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Jeannie -- Oh, this will be fascinating -- because potentially, every injury is a study in biomechanics. If possible I'd love to have you post a link to a video so we can see what "style" of dysfunction we're looking at. And I'd like to know more about the old injury -- to what muscle or tendon? How was the horse injured?

Horses that I have observed who had stringhalt and who were being ridden or just moved around i.e. at liberty or on the longe line, somehow all managed, despite the extra-high lifting of the affected hind leg or legs, to get the feet of those legs on the ground in the proper time, so that the proper and normal, or very near-normal rhythm of the gait is preserved. This would be the first thing I'd need to know about your project -- how far "out of time", if at all, he is at walk and trot.

If you can't manage a video, then at least one or two stills would be helpful. Try to catch him at the height of the hind-limb lift. Also if you don't really know the history of the injury or its exact "diagnosed" location, if there is a visible scar then a photo of that if possible.

Your observations and "feel" for what's odd about this horse will also be necessary. Does he seem stiff anywhere? Does he do anything else odd with any other limb?

And then finally, some basics: breed and age. This will very likely evolve into an excellent threat -- thanks so much for sharing it with me and everyone else. Cheers -- Dr. Deb

Jeannie
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 Posted: Fri Feb 1st, 2019 02:09 am
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Dr Deb, the mare is a rescue,so the exact nature of the injury is unknown, but there is a scar, so I can get a photo of that. Also some other photos and a video of her walking when I see her next week. I"ll let you know my impressions as I go along.
Thanks,Jeannie

Jeannie
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 Posted: Tue Feb 5th, 2019 09:15 pm
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Dr Deb, I sent you a short video and some photos if you think those would be of interest to post. The mare is a 6 or 7 year old Andalusian, it will be interesting to see if anything changes with work.
Best, Jeannie

DrDeb
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 Posted: Wed Feb 20th, 2019 06:13 am
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Dear Jeannie: It's taken me forever long to get back to you on this, although I received the photos just fine and also the video link. However, for some reason the video or the link is glitchy and I can't seem to play it. However, the photos are quite sufficient for purposes of getting some answers to your queries. I post them below so we can all look.

Photo no. 1, showing the tail -- I have to ask you now to verify if my marking the position of the tailbone under that thick hair is about right. I marked it where the tailbone appears to be, and it's of interest because it appears that the mare has had her tail broken (marked "3"). This, along with the other scars/injuries, indicates to me that the most likely scenario for how she got injured was that she flipped over backwards. Not while being ridden, I expect, but rather I imagine she ran backwards and then hit a fence and flipped over the fence. Or possibly somebody was roundpenning her and she tried to jump out of the pen and didn't quite jump high enough, and then executed a sort of barrel roll over the top bar -- I have seen this happen.

So, when she hit the ground I think she not only broke her tail, possibly in two places as my sketch shows. The next injury of interest is the pucker-scar atop her left ischium, marked "1" in the marked photo. This might have occurred because she landed on a rock, or, it presents another possibility, that what we are looking at here is an injury that occurred in a horse trailer, i.e. she ran backwards and slammed into the butt-bar or chain, which would cut and crush similar to the top rail of a fence. In any case, injury "1" is not merely superficial, like the "thumbprint of God" that we were looking at last week on Redmare's gelding's neck. Yes, the subcutaneous fat and fascia have been crushed as they have in Redmare's horse, but the somewhat sharp downward puckering is indicative of a cut that went deep enough to go all the way down to muscle tissue. The affected muscle is the upper head of the semitendinosus.

The next injury in evidence is marked "2", and once again here it seems to me that the most likely scenario is her running backwards into a fence or maybe the lower edge of a butt-bar or chain setup in a trailer. Again, she cut herself deeply enough that we are not looking at a superficial crush or a laceration that only went skin-deep, but instead all the way through and I think quite deeply into the muscle and tendon below. This is the most serious of all her injuries in terms of causing the stringhalt, because it almost certainly involved adhesions and scar tissue that reduce the normal degree of "stretchiness" of the lowest head of the femoral biceps muscle and also, I think, the tendon of insertion of the gastrocnemius at the point where it is joined, or forked with, the Achilles tendon. Shortening of these muscles due to scarring limits her ability to protract the upper part of the affected hindlimb, in such a manner that when the stifle gets as far forward as the damaged muscles will allow it to swing, the tension on those same muscles is such that it forces flexion at the hock, thus creating the classic appearance in movement of mechanical stringhalt. The "forcing" of hyperflexion at the hock is due, of course, to the peculiar anatomy of the hindlimb reciprocating apparatus in the horse (anyone wanting more detail on that, please use the Google search function as per instructions given in the announcement thread in this Forum, entering keywords "reciprocating apparatus" or "sticking stifle").

The other injury that this mare got is shown in the photo of the lower part of the left hindlimb. I have used Photoshop to "stain" the hairless scar so it shows up better. Here again there was a rather deep cut, this time going through the skin and down into the superficial flexor band. Once again, this band -- which like many parts of the hindlimb reciprocating apparatus was once a muscle, but which in the horse develops as a non-contractile, bungee-cord-like elastic strap -- is an essential part of the reciprocating apparatus which, because after injury it shortened up and lost some of its elasticity through scarring, contributes to the stringhalt movement pattern.

Now that we're (hopefully) clear as to the mare's injury configuration, we can turn to the movement photo that catches her in the act of hyperflexing the left hindlimb with protraction. If Jeannie, you are willing to do the somewhat physically demanding hindlimb stretches, they will be of real help to this animal -- even at this late date. I suggest you go back to the Google search and look up Pauline Moore's extremely helpful photos and discussion concerning the right way to do hindlimb stretches -- "right" not only for the horse but also as to minimizing the strain on the therapist's back!

The other thing I would strongly urge you to do is to teach this mare the plie bow. Let's see if she does anything weird with the hindlimbs or perhaps with her lower back once she gets to the stage of making a pretty deep effort. You can't do this too much -- she'll go as deep as any pain she feels allows and this is normal horse thinking. But as such it's useful to us as telling us just as plain as words, what the range of flexibility is for her on any given day.

Another thing that's going to help is backing her in hand. I expect this is what got her into trouble in the first place -- the commonest reason why horses run away backwards is that they get their hind feet "trapped" under their butt when they're being asked to back up, and can't figure out any way to solve that conundrum except by trying to either run backwards, or else rear. What I mean by "getting their hind feet trapped" is, that the rider -- who doesn't know how to teach backing up but can only think of "making the horse go backwards" -- pulls on the bridle and the horse then, instead of STEPPING back one step at a time, LEANS its heavy butt back without picking up either hind foot, and this then traps the feet because the horse can't both support its weight behind and flex the joints of either hind limb in order to get a foot picked up.

So obviously we start this part on the ground and we do not ever ask this mare to back up under saddle until she's perfectly comfortable doing thirty steps backward with you just manipulating the halter with your fingertips, helping her to shift her weight from side to side, which is what neither she nor her original "trainer" knew to do.

Your own question related to lateral work, and of course you will be doing lateral work from Day One because you're going to have to get this mare broke, which she isn't currently, and you do that by teaching it to step under the body-shadow with the inside hind leg. And you teach it to make loose or "drifting" turns on the forehand, and you monitor whether this feels the same to left vs. right (which it won't, of course); and you teach her to expand the circle by leg-yielding outward, and to "drift" from one circle to the other of a "separated" figure-8. And in among this, you get her twirling her head, because that's the natural and normal outcome of changing the bend, which means fundamentally, changing the foot which understeps vs. the foot which receives the bend and the weight.

Please keep us pegged how this goes -- you are another very competent trainer and rider and your reports, like those of Redmare, do nothing but assist other people who would like to learn the art -- the true art, that is, of helping any horse to become a better and a more beautiful ride. Cheers -- Dr. Deb

Attachment: Jeannie Horse w stringhalt marked SM post.jpg (Downloaded 122 times)

DrDeb
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 Posted: Wed Feb 20th, 2019 06:22 am
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Here's the photo of the injury to the flexor apparatus of the left hind limb. I've used photoshop to stain the hairless area of scar tissue on the skin pink, to make it more visible:

Attachment: Jeannie Horse w stringhalt hindlimb SM post.jpg (Downloaded 122 times)

DrDeb
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 Posted: Wed Feb 20th, 2019 06:25 am
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And here is the photo showing the stringhalt movement. The lower left corner of the photo is cut off because the original was tilted so I rotated the image to bring it properly to level, i.e. so that vertical objects in the background, such as telephone poles, fenceposts, and the corners of houses are vertical:

Attachment: Jeannie Horse w stringhalt movement SM post.jpg (Downloaded 123 times)

Jeannie
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 Posted: Wed Feb 20th, 2019 11:39 pm
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Thank you, Dr Deb, for your expert analysis of the photos. I felt her tail today, and did not feel any scar or crook in it, but an accident while going backward seems to be a reasonable hypothesis given her current physical state.
She is definitely stiff when attempting to twirl her head from the right side, but we have been doing a number of ground exercises to help her with that, as well as to release and raise the base of her neck. It's good to know that backing up will help her, hopefully it will get smoother with practice. The stringhalt gets more obvious with tension, if her breathing gets heavy, then it's every step, but if she relaxes and loosens up, she can go for awhile without doing it.
I think the stretches will be good for her; the plie bow is a great idea as she is pretty tight through her shoulders. I've been doing lateral work on the ground with her, as we are waiting on a saddle for her to begin the ridden work. I would prefer to get a lot sorted out on the ground first anyway. It will be interesting to see how we progress, and I will keep everyone up to date as we go along.
Thank you for your advice and kind words of encouragement .
Best,Jeannie

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 Posted: Tue May 21st, 2019 04:55 pm
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Hi Dr Deb, I've had enough rides on the mare to let you know how she is progressing. We did a lot of body/ground work to begin with, getting her to stretch out her muscles, especially in the shoulder and neck. We have been doing Pauline's stretches, as well as the pile bow, which she can do quite well. I also plan to get a pedestal.

Not surprisingly, our first rides revealed no steering, brakes or suspension. Her string halt made for a rough ride as she was out of time with that leg, as you suspected. She is quite crooked, at first not wanting to go right at all. We spend most of our time at the walk, after she warms up the string halt goes away unless we stop, then the first step back to walking it will manifest, then go away again.

She gets very excited transitioning into the trot, which results in the string halt showing up again for awhile. She wants to trot too fast, so I try to slow her down and ask for quiet transitions up, which she is getting a little better at on occasion.

We do a lot of bending exercises, she is getting better to the right. When I ask her to back up in hand, she lifts her left hind higher, but is getting a bit smoother. She has plenty of energy, I have not asked her to canter as I want her to get her balance better before she starts speeding around more. On her own she seems to do a kind of gallope, with both back feet coming forward almost at the same time.

As we make some progress I will try to get some photos or a video to post.

Does the fact that she gets out of the string halt after moving for a while, but has to do it at least once to get going again give any clues as to its cause? Could she just be in the habit of doing it, , if that's not a silly question? I would love for her to get a work up from a vet to identify the cause, it may happen at some point, and I will let you know the results if that happens. In the meantime, I would say she is making progress.

Best,Jeannie

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 Posted: Wed May 29th, 2019 04:19 pm
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Hi Dr Deb,
I understand from your analysis of the mare's injury that scar tissue has tightened and shortened her muscles up enough to cause the flexion at the hock, and thus the stringhalt. Is this consistent with the fact that she can get out of the stringhalt after relaxing and warming up, but stopping even for a second before walking off again will trigger it. I'm a little confused by that, as the muscles would still be warmed up and stretched out.

The horse is 81/2 years old, a little older than I first understood. The current owner got her as a rescue at 21/2 in this condition, also found out she was pregnant after she got her. Do you think it would be worth it to get a vet work up at Davis to get more information about her condition, or would we most likely find out what we have already assumed. It would be expensive, so that's always a consideration, but all information is helpful.


As far as working with her, I understand the importance of the stretching, would strengthening be just as important ? I know from my own working out that I feel tighter afterwards, so always try to do her stretches with her. She is getting better about giving me her back legs, but still has some issues, understandably.

Your help with this project is greatly appreciated.

Best, Jeannie

DrDeb
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 Posted: Wed May 29th, 2019 06:05 pm
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Jeannie, the veterinary community is divided on the causes of stringhalt, although I do believe they all will tell you it's incurable or at least highly intractable. Physical therapy is not high on their list of treatment options since few veterinarians receive any training in it, and I know of only two veterinarians who ride well enough to understand how to use the act of riding (or so-called "trick training") as forms of physiotherapy. Your closest approach on that track would be a good veterinary chiropractor, or if Lauren DeRock is still out there, she is the best veterinary acupuncturist I ever met and that might be your best bet of all.

There are two very different putative causes for stringhalt: one, toxic plant ingestion and two, physical damage. The old, and now totally debunked and refuted, veterinary approach assumed a physical cause and focused on the musculoskeletal system without much consideration of the nervous system. The old treatment was surgery (what else are veterinary surgeons trained to provide, after all) in which the long tendons of the hind extensors were cut. This "worked" about as well as cutting the stifle ligaments or check ligaments, in other words, it didn't work at all except very temporarily. The received opinion in the veterinary literature at the present time is that this surgery is not advisable, so if some practitioner who is not really up on that suggests it, I would dismiss that advice entirely. Assuming a physical cause that primarily involves the musculoskeletal system was my thinking for years but the treatment approach I would employ would be physiotherapeutic (stretches combined with excellent riding that includes transitions and figures, plus possibly chiropractic and/or acupuncture as above mentioned).

Nobody was more shocked and disbelieving than myself when, about fifteen years ago, some Australian researchers discovered that they could induce stringhalt in a test population of horses by feeding them Cat's Ear (a species of Hypericum, a plant that looks like dandelion but isn't -- very common weed on all continents and grows in my backyard here in California and I'm sure in yours also). You can look up all about that in "Poison Plants in the Pasture" if you have a copy.

The difference here is, of course, that the cause relates to the nervous system as the poison in Cat's Ear is an alkaloid toxic to nerve cells. Alkaloid toxins are wierd because, no. 1, there are a lot of them, and no. 2, because they differ one from another only by a few molecules. However, that apparently makes a huge difference as to WHICH nerve cells in the mammalian body they are going to affect. I'm waiting for some researcher to cotton on to this, or maybe it's my own ignorance here as I am not a chemist, and they already have: what I mean is that obviously, you could use alkaloids to specifically "target" various parts of the nervous system (for various therapeutic as well as for different experimental purposes).

There have been subsequent studies which did not corroborate the original Australian research on Cat's Ear. This is also right in line with the wierdness of alkaloid toxins, because when they occur in other plants they also are sometimes benign. This indicates that it may not be the Cat's Ear itself but something in the way of an ergot or mold that grows on (or in) the plant and is seasonal, so that when the 2nd group of researchers gave Cat's Ear to their experimental herd, there was little to no effect. In light of this, I would still be out there in a hazmat suit and rubber gloves squirting every Cat's Ear plant I could find in my pasture (be real careful with Roundup, as it is now known that it is a powerful carcinogen, and also, don't get it on any plant you don't want to kill, i.e. bulk spraying from a tugalong behind your riding mower or tractor might be easier but it's dangerous for both reasons).

Bottom line for your horse is that we do not know which is the effective cause. If it's not terribly inconvenient, during these very nice days of late May and early June you might take a ride to the farm where the horse originated and eyeball their pastures. If there's a lot of Cat's Ear I'd incline to that as a cause. Maybe you can even find the former owners and ask if they can give you details on the mare's injuries which we discussed before; they are the main reasons I'd like to think that in her case we're dealing with a "mechanical" rather than a chemical cause.

Otherwise, all you can do is carry on as you have been, because either way, she still needs good riding and stretches. I have seen (and advised, to good effect I think) two other horses with stringhalt -- they all have gotten better about as yours has, but they never get completely over it. As a parallel, I think you've seen photos I've posted of my gelding Oliver doing the plie bow; due to his early history of severe founder with rotation and consequent shortening of the forelimb flexors, he was almost never able to do the plie bow with the forelimbs straight. Instead, he "spidered" so that although he had his head well back between his forelimbs and the front end of his chest was very much lowered, he went down with bent knees because to do otherwise would have hurt him too much or even torn the flexors. He got better as the years went on, so that by the time he died last February he could sometimes do the plie bow with straight forelimbs, but not every time. Such is the nature of muscle injury, especially where it involves scar tissue, i.e. as with a bowed tendon. The semitendinosus muscles of horses that have any type of "hitch in their gitalong" -- and stringhalt is merely the most extreme or strongest form of that -- essentially have a "bow" in the core tendon.

I don't blame you if you find this "rescue" a bit frustrating but still, if she's a good ride otherwise, there's a use for her. Teach her a bunch of so-called "tricks" not only to help the stringhalt but to help her find a forever owner after your good ministrations! Cheers -- Dr. Deb

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 Posted: Wed May 29th, 2019 11:40 pm
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Dr Deb,
Thank you for your reply clarifying that a veterinarian work up would not result in much more useful information than we already have. I agree with you that her stringhalt is likely a result of her injuries. She was confiscated as a result of a drug bust, so her past life is unknown. Fortunately she has a forever home with her current owner, I am working with her to see what improvements I can make.

I agree with you that the physiotheraputic approach has the most promise of helping her. Perhaps she just gets tense when we stop, so has to work that out to get going again. I will work to see if she can overcome that eventually, and keep you posted as to how she is doing. We are getting a pedestal soon, so tricks are on the menu.

My condolences on your Oliver passing, my horse B is also gone, it is hard, but they teach us so much.

Best, Jeannie


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