What if you were to learn that your horse is living with a hidden malformation? A skeletal abnormality that could be affecting it every day, changing the way it moves, creating a string of other physical problems, and possibly underlying the hard-to-pinpoint problems you’ve been noticing for months or even years ?
And that might even be causing a level of inherent instability that could be putting the rider in danger?
Sadly, this isn’t a hypothetical question. Instead it’s a reality that is only now being slowly uncovered.
And like the proverbial stone rolling down a mountain, the issue is gathering momentum as the equine industry, owners, breeders and researchers learn about it.
- It’s a skeletal malformation and it can’t be corrected.
- It’s congenital, ie inherited, so is present from birth.
- It has been in some lines of TBs for hundreds of years.
- It creates biomechanical issues due to asymmetry and lack of anchor points for key muscles.
- At its worst, it can contribute to neurological issues such as Wobbler syndrome.
- Some horses are so unstable, they are more prone to falling (not good news for jockeys).
- It can cause constant pain and associated behavioural changes.
- It’s primarily found in Thoroughbreds, Thoroughbred crosses and Warmbloods, but has also been identified in European breeds, Quarter Horses, Arabs and Australian Stock Horses.
The problem behind this is ECVM, a congenital malformation of the C6 and C7 cervical vertebrae (ie, base of neck) – and it’s pretty nasty.
I’ve written about the work of Sharon May-Davis on this blog before and here I’m going to do so again. Through her many dissections per year, gross anatomist Sharon has become the first person to comprehensively document and quantify this problem.
In doing so, and publishing her findings in peer-reviewed journals, she has triggered a minor research avalanche as others take up the subject.
Update: since this article was published in July 2017, this malformation has been labelled Equine Complex Vertebral Malformation (ECVM). Some amendments have been made to include this term.
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Twenty years + of research into ECVM
Sharon May-Davis’s path with this research began some 20 years ago. In February 1996, a Thoroughbred called Presley came down unimpeded in a race in Grafton, NSW, fracturing his pelvis, a hock bone, and right front fetlock.
Three years later, Sharon examined his bones, and saw something strange in his last two cervical vertebrae and his first ribs.
Fast forward to 2014, when Sharon published the first of her four peer-reviewed papers in the Journal of Equine Veterinary Science, concerning a congenital malformation in the sixth and seventh cervical (neck) vertebrae.
Although the problem had been mentioned briefly in papers, this was the first time that a researcher had accurately described and quantified the problem in its various forms.
Sharon’s unique perspective, gained as an anatomist who dissects between 15 and 20 horses per year, had certainly placed her in a position to do so.
The horse’s seven cervical vertebrae – made simple
Horses have seven vertebrae in their necks, labelled C1 to C7. Of these, four have unique shapes. Most horse people are familiar with C1, the first vertebrae known as the atlas, as it can be both seen and felt by hand with its distinctive ‘wing’ at the top of the neck.
Almost as well-known is C2, the second vertebrae, known as the axis.
Both atlas and axis have unique shapes for a special reason: they support the heavy skull and anchor the muscles that control the head’s movement.
Heading down the neck, C3, C4 and C5 are broadly similar in shape, with each being a bit shorter and blockier than the one above.
However, C6 and C7 are both slightly different on the ventral (lower) side, for here they provide insertion points for muscles arising from the chest.
- C6 has transverse processes (the protrusions extending outwards) that are different to those of neighbouring bones, with two distinctive ridges running the vertebrae’s length. C6 also has two large transverse foramen, the openings that the arteries pass through.
- C7 is the shortest and squattest cervical vertebrae of all. Its transverse processes are shorter, while there are also two facets that articulate with the first ribs. C7 has no transverse foramen.
At least, that’s how the vertebrae should be in a normal horse.
So, what is wrong with the malformed C6 and C7 vertebrae in ECVM?
In certain horses, these last two vertebrae are rather different, being malformed.
Sharon has identified the manifestations of this problem as a congenital (inherited) malformation affecting some Thoroughbred horses, and horses with Thoroughbred blood in their ancestry.
In C6, there is a problem with the two ridges of the transverse processes, as one or both can be partially absent.
When both are partially missing, it is common for one or two ridges (ie, parts of the transverse processes) to appear on C7 instead.
Also, the articular processes (the oval surfaces on the upper side, where each vertebrae links to its neighbours) can be radically different sizes. There can also be an additional arterial foramen or two.
The level of asymmetry can be radical.
The secondary problems the ECVM malformation causes
Being at the base of the neck, the asymmetry of C6 and C7 can cause alignment problems all the way up the vertebral column, leading to osteoarthritis of the articular facets.
It can also contribute to Wobbler Syndrome (Cervical Vertebral Stenotic Myelopathy), due to narrowing and/or malalignment of the vertebral foramen/canal, the opening through which the spinal cord passes. Not all Wobbler cases have this particular malformation, though.
A further problem is that the lower part of the longus colli muscle, which is involved in flexing the neck, would normally insert on the transverse processes of C6 and C7. When these processes are malformed, the normal insertions are not possible.
This means there is a serious symmetry problem in the junction of the thorax and neck, which can have a deeper effect on the horse’s neurology and proprioception, as well as respiration.
In a few cases, horses with both the C6 and C7 problem also have malformations of the first sternal rib, on one or both sides. This can cause problems beneath the scapular and further issues with muscular attachments.
Associated stability problems can have far-reaching consequences for the horse, not to mention some serious safety issues for the rider. The safety issue can’t be stated often enough.
(Add to this the fact that the horse’s nuchal ligament lamellar does not attach to C6 and C7, and often only feebly to C5, then you can see that this is a high level of instability in a critical area. Read more about Sharon’s findings on the nuchal ligament here – How the Anatomy Books Unintentionally Fail us Over the Nuchal Ligament.)
Read on for information on for signs that this problem may be present in the living horse…
Why isn’t the C6-C7 problem more widely known ?
Why hasn’t this problem been noticed in regular veterinary interventions?
The answer is quite simple. While neurological issues may have been diagnosed, the exact cause has often remained hidden.
Both Thoroughbred horses and Warmbloods are known to have higher incidences of Wobbler Syndrome than other breeds, and while this is certainly not always due to C6-C7 malformation, the malformation has been found in some when dissected.
For example, the following dissection image appears in a veterinary account of large animal spinal cord diseases. It clearly shows a malformed C7 vertebrae, very similar to the one in the above image, but without giving any further categorisation.
The difficulty lies in the deep location of the lower cervical vertebrae. While normal radiographs can show all or some of C6, they are unable to penetrate the deeper tissues beneath the shoulder to image C7.
Nevertheless, the malformation can be identified in radiographs of C6, once you know where to look.
Since Sharon’s first paper appeared, the School of Veterinary Medicine, University of California, Davis, has reviewed its history of radiographs from horses with Wobbler Syndrome.
Researchers found that 24 cases out of 100 (close to 25%) showed malformation of one or both C6 transverse processes. This study also clarified how to identify the problem on standard radiographs of C6.
In another study, the Faculty of Veterinary Medicine, Utrecht University, completed CT scans on horses’ necks and found the various forms of the malformation in 26 horses out of 78 (33%). Unlike radiographs, the CT scans enabled identification of the C7 and first rib issues, although of course this imaging was conducted post mortem.
Is this rare, or are many horses affected?
While the problem has been identified primarily in TBs, it affects most breeds with TB blood in the ancestry to some degree.
Sharon May-Davis reports that to date, published, peer-reviewed journal papers have tallied 136 out of 471 horses as exhibiting congenital malformation of C6.
These have been in a range of breeds including Thoroughbreds (39%), Thoroughbred crosses (27%), Warmbloods and European breeds (30%), Quarter Horses (11%), and Arabs (11%). Standardbreds have also shown the problem, although the numbers included in studies are very small.
A common question is whether it’s known which TB lines predominantly carry this problem. The answer is: Yes. However, it is now so disseminated amongst the modern equine population beyond TBs, that it is of little help to identify them.
“Eight Belles… might have been genetically predisposed to breaking down.”
Exploring the views of a TB lineage expert, this American article from 2009 asks why certain TB lines were prone to breaking down on the track – Eight Belles Breakdown: A Predictable Tragedy.
It must be remembered that these horses are those already brought to veterinary attention and/or euthanized for a related or unrelated reason, so the percentages may be higher than those for the general horse population. At the same time, the malformation might have played a major part in the horses’ decline, due to the many locomotory and postural problems it can lead to.
How do we identify these horses in life?
It’s all very well looking at these bones post mortem, you might say. Yet how can I tell if my horse has this problem? Or a horse that I might want to buy?
Some answers are forthcoming. As Sharon has frequently assessed horses before dissecting them – usually from video – she has been able to observe that many of these horses lack stability. (Indeed, in many cases, it is this very instability has directly led to the horse being euthanized, and ending up on the dissection table.)
As her research has progressed, she has also been able to identify many biomechanical and locomotion traits that make these horses ‘suspicious’ or at least ‘of interest’. Unsurprisingly, these problems have been particularly noticeable in horses with both a malformed C6 and C7.
For owners and equine professionals, here are some signs that can raise initial suspicions. All can also be caused by other problems, so a group of signs is more common than an individual indication.
- Some of these horses have a problem with standing square in front, and will always keep one foot further forward. This can persist despite all attempts to improve the horse’s body and to train the horse to halt squarely.
- Horses with the more serious malformations will often stand base-wide. Such horses can become very unbalanced on uneven ground, and sometimes in work. They easily become unbalanced when a hoof practitioner works on a forefoot.
- With such asymmetry in the skeletal structure, these horses have serious lateral flexion issues that can’t be overcome. When required to elevate the forehand, many will experience difficulties, due to the absence of correctly inserted musculature and incorrect articulation through the joints of the lower neck.
- A high level of asymmetry may be seen in the shoulders, with one scapula sometimes positioned very wide, with no improvement after chiro, osteopathy or bodywork. This is particularly so with the C6-C7 problem and associated first sternal rib abnormalities.
-
The ventral aspect of the neck may show some scoliosis. There may be scoliosis along the entire spine.
- There may be an obvious scoliosis to the underside of the neck.
- The problem may lead to heavily asymmetric loading of the forefeet, so may be accompanied by a severe high foot/low foot issue (this is not in itself a sign of the C6-C7 problem).
If you suspect your horse has the C6-C7 issue
First, note that many horses do just fine with a C6 problem. It is those with the bilateral C6 and unilateral/bilateral C7 issue that tend to show the more worrying problems.
If your horse is showing ongoing signs of instability, it’s important to seek veterinary advice, so that neurological issues can be ruled out. (As this a recently recognised problem, it may be worth printing out the abstracts from the journal articles listed at the end of this page and handing them over.)
If the more severe malformations are identified by radiograph, it is important to remember that in some cases this can cause discomfort and pain to the horse, and it is not going to improve over time.
On the contrary, the cervical vertebrae of some older horses with the C6 and C7 malformations often display advanced osteoarthritis of the articular processes, as shown in the header image of a 19-year-old Thoroughbred’s malformed C7.
Where does this knowledge take us?
At the moment, that question is wide open. The findings published by Sharon May-Davis have triggered ongoing research on an international level. There are certainly ramifications for breeders in more than one equine sporting industry.
See Sharon’s December 2020 presentation on ECVM here (article continues below):
Connections have been made with a number of falls on the racetrack that have caused injury, and worse, to both horse and jockey, as well as other runners. Similar things can be said for the sport of eventing, where unforced errors can have equally catastrophic effects.
It is entirely possible that at higher levels, pre-purchase examination radiographs will come to include a check on C6. While it’s not possible to radiograph the deeply positioned C7, we do at least know that this will only be present if the C6 anomaly exists.
Vets in some countries are proving faster at picking this up than others. While papers are being published, it clearly takes some time for information to filter down.
And until more is known, this problem is being unknowingly propagated every breeding season.
Of course, many horses harbouring the milder manifestations of this problem at C6 level are functioning very well. All horse owners can do is be aware that this issue exists, make use of this information if a problem arises, and await further research findings.
Sharon May-Davis’s research includes the rarely documented arthritis affecting the elbow joint of ridden and driven horses – Revealed: the Common Equine Arthritis You Won’t Read About in Textbooks.
Plus, read about the effects of hard race training on Thoroughbreds – Buying an Ex-Racehorse: Can You Spot the Major Physical Issues? – and advice from a seasoned trainer on rehabbing your horse once it’s arrived at your stable – 8 Golden Rules for Helping Your Thoroughbred Get Right Off the Track.
Literature on the malformation
Peer reviewed journal articles on the C6-C7 and related first sternal rib issues.
- The Occurrence of a Congenital Malformation in the Sixth and Seventh Cervical Vertebrae Predominantly Observed in Thoroughbred Horses, May-Davis, Sharon, Journal of Equine Veterinary Science , Volume 34 , Issue 11 , 1313 – 1317
- Variations and Implications of the Gross Morphology in the Longus colli Muscle in Thoroughbred and Thoroughbred Derivative Horses Presenting With a Congenital Malformation of the Sixth and Seventh Cervical Vertebrae, May-Davis, Sharon et al., Journal of Equine Veterinary Science , Volume 35 , Issue 7 , 560 – 568
- Congenital Malformations of the First Sternal Rib, May-Davis, Sharon, Journal of Equine Veterinary Science , Volume 49 , 92 – 100
- Ex Vivo Computated Tomographic Evaluation of Morphology Variations in Equine Cervical Vertebrae, Veraa, S. et al, Veterinary Radiology & Ultrasound, Vol. 57, Issue 5
- Prevalence of Anatomical Variation of the Sixth Cervical Vertebra and Association with Vertebral Canal Stenosis and Articular Process Arthritis in the Horse, Spriet, M. and M Aleman, Veterinary Radiology & Ultrasound, Vol. 57, Issue 3
- Anatomical Variation of the Spinous and Transverse Processes in the Caudal Cervical Vertebrae and the First Thoracic Vertebra in Horses, Santinelli, I. et al, Equine Veterinary Journal, Vol. 48, 45–49.
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Fascinating article
Oh Wow!
This has answered so many unanswered questions relating to my 23yr old mare! V long story short – she is a 16.3hh, TB x Hannoverian and has this condition.
She has been in full retirement for 3 years now and has been fine (apart from sleep deprivation/narcoleptic symtoms due to lack of laying down) and I have known her days are very much numbered 🙁 She is a dominant mare and until this spring has been able to maintain this position with no physical problems but when her long term field mate left her in Spring the added physical stress of ‘keeping order’ led to fore limb unsoundness (something that was an occassional and unanswered problem throughout her ridden ‘career’ but is now clearly explained above) it has taken several weeks of danilon to get her ‘sound’ again but then a flock of sheep escaped into their field, causeing havoc and aggrevated the unsoundness again so is back on Danilon. I have vowed that I would care and provide for her as long as she was sound and did not need daily meds so I fear we are now bordering on that and this may well be her last summer :(( Your article has clarified so much though I do now feel that I will be able to make the right decision at the right time alongside my vet – thank you.
Minor quibble–congenital and inherited are not synonymous.
Congenital conditions *may* be inherited, but not all of them are.
For example, cerebellar hypoplasia in kittens may be the result of a feline distemper virus infection of the dam during pregnancy.
Inherited conditions are congenital in that they are present at birth, but may not manifest until later (for example, Huntington’s Disease in humans.)
That said, I expect that there is at least some degree of inheritance at work in cervical vertebral problems of the horse.
Thank you. The error is mine.
This issue has been identified as passing down certain lines, although it does not manifest in every horse in those lines. Thankfully, the skeletons of many outstanding racehorses have been preserved, enabling identification of the issue in some prolific lines.
This is so helpful. My horse is a 18 year old mare tb warmblood x who is 5 months into retirement because of undiagnosed “instability issues”. She won’t square up in front and exhibits much of the behaviours you’ve described. She would fall after being ridden usually at the walk or just standing around (mounted) after a hack. Then it got more serious. Falling at the canter – like no legs were underneath her at all. That is when we pulled all riders and began the attempts of figuring out what was wrong. We never found anything except she won’t stand up straight now. She doesn’t lock out her knees super well anymore either. Her issues were WITH riders so she does ok hanging out with no riders anymore obviously. I so appreciated this information.
Hi, thanks for telling us this. It does sound likely, doesn’t it? I hope it helps to have some inkling of what could have been happening. Retirement is a good decision and I’m sure you’ll notice if she exhibits pain in the paddock.
Hi Heather,
I replied to this earlier, I thought, but it hasn’t appeared.
Your mare certainly sounds like a candidate for the full C6-C7, doesn’t she? We’ll be posting details of the radiographic protocol next week, so if you were to seek additional confirmation, that might help.
However, it does sound as if you’ve made the right decision based on the signs and in the interests of safety for riders and horse. It’s possible that she may worsen further with advancing years, but you’re clearly watching her closely.
Thank you for posting this.
Hi, I thought I would check in. It’s 3/1/2020 my mare will turn 21 on 5/1. She is still mostly retired. She got so bored not being ridden I decided to try walking and super light hacks on flat ground only. Our rides are 15 minutes or less mostly all walking some trotting. Lots of transitions and barely any cantering. She does ok. I can’t do long and low or ride on the buckle. I know I risk her falling but we don’t jump or go anywhere uneven. For now she still does ok. I watch her closely in turnout and know she could very well be affected as she ages.
As a Canadian Sport Horse Association (CSHA) performance horse breeder, I would like to know which Thoroughbred lines predominantly pass on this problem. I think it is important even if so many performance horse breeds have Thoroughbred in them. As a sport horse breeder I have never seen an issue with any of my equines, but I would like to be able to knowingly avoid certain lines if I know of a “possible problem” (which I still feel hasn’t become a serious issue yet).
Hi Vicki,
I got a clear warning not to name the Thoroughbred sire line !
Even within the last month we (European colleagues and myself) got another warning to be careful with our research and to go slow. With a potential 30% in Warmbloods, there are a lot of breeders that stand to lose if this congenital malformation became a reason for loss of purchase. Which by the way has just happened at a major European Warmblood auction!
Remember, mine and other necks are on the line and when I got my first informal death threat in 2005, I had my children in the car.
So I would recommend the congenital malformation to be detected by radiographs with the right technician who can read them.
At this point in time, the radiographs and CT scans have all revealed an abnormal vertebral canal. In other words, not one had normal vertebral canal aperture for the spinal cord to pass through nor Thoracic Inlet aperture. Furthermore, the preliminary radiographic protocols written and accepted for a Japanese journal will be posted next week in English. This paper describes the radiographic view and also, as per a previous paper (re “Longus colli”) the potential influence on the trachea caused by this congenital malformation.
This later paper describes asymmetrical: biomechanical forces; entheses patterns, neurological dysfunction among other issues and the table that Jane posted identifies these also. This paper along with the 1st sternal rib paper notes clinical findings pre and post mortem along with a maternal link. Including embryonic mortality and confirmed C6 and C7 spontaneous abortions of 3rd trimester foals.
The 3 spin off papers from UC Davis (De Rouen et.al), Utrecht Holland (Veraa et al.) and Italy (Santinelli et al.) confirm these congenital malformations and took the findings into other breeds; Warmbloods, Standardbreds, Arabians and Quarter Horses to name a few. So in total 7 papers on the subject.
In fact, I have personally seen or know of it in New Zealand, Japan, UK, USA, Europe and of course Australia.
Research is a slow and time consuming journey and it took 15 years from discovery to publication and I think this was a miracle considering the number of road blocks I encountered.
Cheers
Sharon
Hello Sharon, this is a fascinating subject. I am an equine thermographer and thermal imaging can show root nerve compression/damage through changes in heat patterns in the corresponding dermatome, I would love to discuss this further with you. Regards Elaine Hall
I was told that a study at New Bolton Center from 1976-80 might also be related to this issue. They were trying to recreate wobblers.
If you click on the link about Eights Belles, it highlights the seemingly problematic bloodline.
Sharon I am so grateful for your research and I am so sorry you have been threatened. I am sure I speak for others when I say we appreciate your skills, training and intellect. It is not always easy to be a researcher, especially a good one.
It is not known to be a serious problem because people are unaware of it – it doesn’t mean it isn’t there! The symptoms can be extremely subtle to start with and can progress very slowly. However, the symptoms are also the same/similar as many other issues that can present in horses or even develop as a consequence of the condition e.g. muscle soreness in the neck – this could be ‘blamed’ on any number of things and vets ‘treat’ the symptoms but not find the true underlying cause. It is a very complex condition and must present itself on many different levels thus making it even more difficult for the vets. More research and understanding of this condition can only lead to better veterinary care and could lead to identifying the ‘wonky’ gene for future breeding programs. Please do not think that because you have never seen any issues with your equines that it isn’t present – it really can be that subtle especially in the younger horses whose bodies can initially ‘adapt’.
A friend sent me this link. I was just forced to retire my homebred 8 yr old, once in a lifetime horse, due to as the vet put it “severe proliferative osteoarthritis of the cervical facet joints at c6-c7”. It explained his erratic behavior through out his life. The attending vet at New Bolton Center in PA, USA said his will progress and eventually severely limit the spinal cord. The one thing it really explained is his lack of topline muscling. Some vets would notice the dragging of the right hind and blame it on stifle issues. The answers came when a professional rider finally believed what I was saying, and knew exactly where to go for a diagnosis.
I am so sorry to read this, Fay. I know it won’t help with the loss of your horse (or at least, your riding partnership), but I do hope Sharon’s research helps you to make more sense of what’s happened. If you still have the radiographs, we’ll be uploading more details on interpreting them next week (see Sharon’s response to an earlier question).
I feel like I’ve joined a support group, I thought my horse was just a freak thing, and now we are learning it is much more common than thought. When the vet said it was from the breeding, I was shocked, and got a bit defensive. I had a wonderful mare that was not diagnosed with this, and as far as I was aware, neither was the stallion. Now I’m learning that many have mild symptoms, and it’s possible that my mare learned to deal with it, and the untimely paralyzing in the stallion, my have been the indicators that we were previously not aware of. When I buy a new horse, I feel like it would be a better bet to xray the neck rather than the hocks.
AND, yes, I do have the x rays.
Hi Fay, we’ll be posting the article on reading the radiographs in a few days… I just need a bit of time to set it up.
Wow, so fascinating and heartbreaking at the same time. Thank you for all of your hard work. Between this and the research being conducted by Equiseq on the genes involved in muscle myopathy, I am losing hope that there are any sound Thoroughbreds (or any horse for that matter). : (
Hihi,
Is there any reason to be worried for the cold blood, smaller breeds, like the icelandic horse?
Or has there been no research on these breeds?
I had a 4 year old welsh cob gelding, put down a few months ago, he had it. Revealed after section. All his problems made sense after knowing this and reading about this. He had malformation of both c6 and c7. I had never heard of it before…
I am so sorry to read this, Annette. It must have been severe for him to be lost at such a young age. It is hardly a consolation, but at least you have this understanding now.
Thank you <3.
We struggled with it from we bought him as 1,5 year old. All the time he had symptoms on and off of something being wrong.
Section revealed an allready on going artrosis in 6 of his legjoints i various legs.
Could anyone give me more information on the signs that there horse was showing before the decision to put them down? My horse has the c6 and c7 and I want to put him down but I dont know of I can justify doing then when he seems fine. Thanks
So typical of the litigious society we have become. I get that it represents income to the folks whose line it may predominate, but SERIOUSLY?!?! What is more important, the fatness of your wallet or the well being of the animal and the people who may be around them?
While I see why the industry wants to protect its interests, I have to agree with the frustration of Betsy barker…at least knowing what bloodlines seem to carry this potential would give buyers the knowledge to know to look for this before buying a horse. Buying and breeding horses are both challenging enterprises. That knowledge would benefit both, I would think.
I have an 8 year old mare I bought as a weanling for dressage, who we noted had quite asymmetrical shoulders after starting her under saddle at 3.5, from the top she appears to carry her neck from the withers out to the left then bends her head to the right at the poll. She has a lot of trouble flexing and bending. She has had multiple odd lameness issues coupled with back end weakness, soreness and a muscle bulge on the right side of her neck, neck ultrasound showed arthritis on the facet joints, inflammation C6/7 and C7/T1, injected twice with minimal changes. Now unable to collect or elevate neck comfortably. My trainer recently felt she looked neurologic/off behind and suggested we test for EPM, Lyme’s, anaplasmosis, basic labs and we did a full physical and neuro exam – all negative. I’ve actually put her up for sale as I feel she is just unhappy in the work I’m asking her to do. She is ok just tootling about on loose contact. Could this be her problem? Now what?
Have you x-rayed? That’s really the only way you can be sure, sadly.
I want to say a public “thank you” to Sharon May Davis, Cat Walker and you, Jane. I only just found all their research articles and your website in the last 2 weeks and as strange as it may sound it brought a huge relief.
I am a human doc and Alexander Technique teacher and have spent many years working with horses and their riders. During that time I was very often frustrated by what I was seeing and feeling relative to discontinuities in the neck-body connection as well as the neurological presentation that frequently came with it. I think between 2011-2013 there were upwards of a dozen horses whose lives I was a part of that had to be retired or euthanized due to these issues. The necropsy usually revealed C-6, C-7 stenosis but there were no malformations mentioned other than one horse with a huge cyst in C-7. ( Doesn’t mean they were’t there just that they weren’t recognized.)
It was validating to read just how many horses have been affected by these anomalies after having been given the stink eye by vets more than once for suggesting that I thought a horse had a neck issue. I am encouraged that institutions like UCDAvis have done follow up studies and hopeful that the dissemination of these findings hits “critical mass”. And hope that looking for them becomes a part of every prepurchase exam to save potential owners from the heartbreak of having to watch their equine friend struggle.
I know for a researcher to gather enough data to publish takes an abundance of time, patience dedication and sweat equity in this case to do a multitude of dissections. From what I can discern from their writings and generosity, for Sharon and her proteges it is a labor of love stemming from commitment to the horses and to the people who love them and want to do the best for them. I have tremendous gratitude to them. And to you Jane for creating this website and providing the information.
Many, many thanks.
Thank you for your comment. You are very much part of this story and I’m sure you’ll continue to be so, as you pass this information on. What you say about receiving ‘the stink eye’ highlights the fact that certain problems don’t officially ‘exist’ until they enter the canon of published, peer-reviewed veterinary literature. Fortunately, the field of genetic research is burgeoning in animal science, and work that’s already being done to a huge extent in livestock will surely start to happen more in the equine field too. It simply has to. As a research field, we can be so slow to adapt to new research approaches that are happening in other species’ research, and it takes ‘outsiders’ to come along and shake the tree.
But I am digressing into my own sabre shaking (more on that next year!!). Back to topic: Sharon does something pretty unique in dissecting 15-20 horses a year in a classical approach to anatomy, rather than in-and-out autopsy to identify a problem’s cause. Read earlier research and it’s clear that anatomical anomalies have been noticed along the way (how could they not be?), but it has taken her perseverance and uniquely analytical mind to not simply quantify the problem and understand its biomechanical ramifications, but to work through the implications in breeding lines and history, and impact upon other breeds, worldwide. I still marvel at the fact that I migrated to Australia 10 years ago and attended my first event, a skeletal dig, with Sharon within 6 months. We now share our research journeys and are friends. What strange paths our life’s works can take us!
Thanks for your reply! Yes, genetic research is really taking off. A decade ago who would have thought anyone could send in a spit sample and $200 bucks and get their ancestry info and their raw genome data? As frustrating as research can be it is indeed an exciting time.
But now I digress!
I was pretty sure that Sharon took a classical anatomical approach after looking at some of the photos in her published articles. Thanks for the verification.
I have been aware for some time that anomalies exist. What is striking to me is how frequent they are. (The absence of the C-6,C-7 nuchal ligament lamellae in every single horse she looked at for the study boggled my mind….. when did it disappear, and why? )
And yes! taking the next steps from anomaly discovery to biomechanical consequences to breeding implications is truly herculean, truly amazing!
It is great to know that there are a number of you there in Australia doing this work who are friends. Having friends who share our journey and provide support and a sounding board is a real gift!
Thank-you very much for this article, it really has helped answer some questions I had about unfortunately having to euthanize my very talented 3 1/2yr old warmblood. He was recently diagnosed by X-ray to have abnormalities of c6-7 accompanied by arthritic changes causing neurological symptoms. I purchased him as a weanling and have been having a hard time accepting what has happened and questioning whether this something that was caused or could have been prevented somehow? He had some of the mentioned symptoms, standing slightly toed out, wearing his hoof on the inside, always seemed to prefer standing with one forefoot forward, one high foot (developed a club) one flat foot, intermittent unexplained migrating front end lameness when started under saddle. Hoping the post-mortem provides more answers and teaching opportunities to learn from his condition, but have taken comfort from this article and in learning more about this debilitating condition.
I am so very sorry to read this. Nothing can change the outcome for you, but understanding does go some way towards emotional resolution. There has been a fair bit of discussion on the Facebook group about how this can be mitigated with younger horses. However, in the worst cases, not much can help at all really, as the problems seem to worsen with passing years.
I’m so sorry for your loss, just heartbreaking. Please know you ar not alone and our thoughts are with you.
HI there
Are you in Australia? I would be interested to know which vet you used to X-ray and diagnose this condition. I have a young horse I don’t want to pour hours into until it is confirmed he doesn’t have this.
kind regards
Thank you for publishing your article about X-raying. It is greatly appreciated. 😃
It was Sharon’s idea to post the radiographic protocol, so that this vital information can be passed on to vets.
My horse was just diagnosed with severe changes at the C6/c7 joints. He is a coming 7 year old Bavarian WB, doing dressage. He is showing mild neurological symptoms and intermittent lameness under saddle. He has had trouble when being asked to collect more and will switch leads when asked to straighten in the canter. The meyelogram is scheduled for later today.
Has the basket surgery be attempted for this malformation? Is there any chance it could help? I want to try joint injections first, has there been any success with that approach?
I have a horse diagnosed with this and injections were tried. In his case, I did not notice improvement with injections. OsPhos is another option.
On a side note, Seattle Slew was probably the most famous horse to undergo basket surgery. His condition was said to be from arthritis, but it is interesting to note the original surgery was done at C6-7. So I am wondering if he always had the malformation and just did not have symptoms until late in life (he was 26 at time of surgery.)
I’d agree with that – the development of cervical arthritis will often follow C6-C7, and this causes massive problems even when the original cause might pass unnoticed.
Wow…I have a 6 year old mare who had EPM (confirmed by titer blood work) as a 6 month old filly. Two rounds of medication and MUCH physical therapy afterwards brought her back to 1. no longer falling when running in mud 2. no longer clipping her front fetlocks severely 3. no longer dragging her hind toes. 4. No longer “pacing”
I had to teach her to pick up her hind feet – she seemed to not know where they were – but if I constantly tapped on her feet she had a better sense of what was being asked of her. When brushing her tail, she cranks it around to the right side.
She has had two foals – the current foal is 2 months old…it was a difficult delivery (big baby) and she began stepping short on the right hind afterwards. And she occasionally has been pacing – am walking her over poles with her head low and walking up hills etc. and the pacing is leaving.
She is half mustang and half quarter-pony. While EPM was confirmed by bloodwork, I find it striking that the same symptoms originate from C6-7….I always wondered “where” in her neck the EPM nerve damage was located.
I am a cold laser therapist – arthritis and nerve damage are helped by cold laser therapy….helped not cured. It is worth it to me to begin laser treatments on my mare’s neck at C6-7 …before I was “shooting in the dark” but now I have a suspected target 🙂
Hmm…just commented about my EPM survivor…
We also have a Quarter Horse who is “quirky”….he LOVES to have his head scratched between his ears…I mean abnormally so! When you brush his forelock he rubs his head up and down on the brush – begging to be scratched between his ears and forehead.
Also quirky – when brushing his tail – his tail vibrates. Its like his tail shivers or quivers when being brushed, especially when the tail hairs are tangled.
I have noticed him standing with either one or the other foreleg in front of the other. We thought this was due to having had severely underrun heels (been correcting former bad shoeing) and a severe quarter crack.
He used to walk “toe down first” but now with better shoeing he walks normally with heel down first.
He has prominent withers and a prominent spine right between the points of his hips. He’s well muscled everywhere else but not along his topline.
I wonder if he’s got C6-7 issues
Thank you so much for your research. I realize it is your passion but, you still have my gratitude. You will be added to my prayers for your safety. I have experienced a shock myself after witnessing many hoof/leg dissections under instruction, to discover that many of our reference books on the subject are just plain incorrect even to the identification and labeling of structures. Never mind their theories on operation. I have a now 28 yr old TB with so many of the symptoms you discuss and your research answers many questions. Thank you!
Sharon May-Davis gives the equine community so much of her knowledge, time and energy. We are incredibly fortunate to have her here in Australia, as are horse owners in New Zealand, Europe and the UK, where she works regularly. With digital communications, we can all now help by taking her findings to our online communities and sharing these vital messages on horse anatomy, health and care.
Has this been found in foals? Is it present from birth or as the foal grows does it develop? I’m curious about the link to hi/lo horse’s since they will have a consistent grazing stance. Could that be the cause of the malformation in a growing horse? Have only mature horses been dissected?
Sharon has found this in stillborn foals and late aborted foetuses. It’s a congenital problem, so inherent to that horse from birth. Yes, the grazing stance is one possible indicator (ie. not all horses with high/low and scissored grazing stances have this problem, and not all C6-C7 horses show the grazing stance). However,grazing stance is NOT a cause, as this is congenital, not developmental. I hope that helps to clarify!
I wonder if there is any link with Neonatal Maladjustment Syndrome. My sister and I have four TB crosses all by the same sire, closely related to Northern Dancer, and although they have been healthy and functional all of their lives, I have always felt from a Cranio Sacral Therapy perspective that there is something odd in their necks. One of them did have severe NMS at birth. We are always careful not to ride forcefully or use the reins to ‘create’ a head carriage and they all strengthened up in their own time. I am certain with three of them that forcing them would have caused damage and behavioural problems.
Head shaking syndrome is another condition I have found to be associated with neck issues.
Thank you for your work!
Afgelopen donderdag met mijn 11 jarige merrie naar de kliniek geweest voor onderzoek. Ik had het vermoeden dat de problematiek die ik met haar ervaar in de benen zat. De diagnose is verrassend… Artrose
Omschrijving patiëntverslag:
Onderzoek Paard is slecht bespierd in de bovenlijn. Op harde loopt paard voor vrij kort. Wel gelijk over de benen (niet kreupel, wel scheef)
Monsteren=- Harde voltes=- Wel linker buiging. Longeren op zachte ruimer doch bovenlijn
is te strak, met name de hals. Galop overkruist, vooral rechtsom. Buigproef RV +/-
Overigen zijn-. Passieve bewegingen rug mogelijk, niet pijnlijk. Hals caudale deel niet te
bewegen, zowel niet actief als passief. Vooral naar rechts belemmerd. Forse blokkades
C567 disorder rechts. Echo hals geeft C45 links vocht C56 L vocht (=v) en arthrose(=a), C67L v, C7T1L v, C56 R
v+a, C67 R v+a, C7T1 R v+a. Op Röntgen zijdelings hals C45 +/- opbouw facetgewrichten,
C56 +, C67 + (+=vergrote facet gewrichten met verbrede gewrichtsspleet). Uitprojectie
röntgen geeft vergrote facetgewrichten met verkleining tussenwervelruimte op C45 L, C45
R +/-, C56 re en C67 re. Conclusie echo en röntgen onderste deel hals arthrose met
zwaarte punt C56, C67 vooral rechts.
Aangezien er tussen klinisch onderzoek, zonder zadel en rijden, geen kreupelheid te zien is
en wel fors met rijden is de rug en/ of zadel ook nog verdacht. De kreupelheid op de video
kan dus komen vanuit de hals, rug en /of zadel.
Advies:
-Voor de voorvoeten Teen inkorten en op ijzers.
-Novacam 2 weken 1x daags voor 600 kg
-Hals is nu ingespoten C56,67 li+re met echo begeleiding. Komende 2 dagen alleen los
aan de longe. Vervolgens kleine week aan langere bijzet. Daarna aan normale lengte van
bijzet. Na 2 weken kan er ook weer begonnen worden met wat rijden na het longeren (bijv
2x per week 10 min). Indien dit meteen niet goed gaat is het advies eens te kijken om met
een bare-backpad te rijden. Als dat beter gaat moet er gekeken worden naar het zadel.
Indien dat niet beter gaat moet er ook naar de rug gekeken worden.
-Sowieso hals niet laten kraken/ manipuleren. Als gevolg hiervan kunnen kleine stukjes
afbreken en het gewricht alleen maar meer irriteren. (ben zelf ook osteopaat en arthrose is
een contra-indicatie voor manipulatie).
Ik heb de merrie pas 4 maanden. Ik ben op zoek naar antwoorden, mogelijke therapie en ervaringen. Ik vraag mij uiteraard af waar dit probleem vandaan komt. Mijn eerste gedachten was verkeerde training (te veel druk) en/of mogelijk trauma. Ik heb zoveel vragen…Kan het dier pijnloos leven met de aandoening?, is therapie mogelijk?, zijn er gradaties (van milt tot ernstig). Erg blij dat ik deze site gevonden heb!! Zeer informatief en leerzaam (ook voor mijn eigen werk als therapeut).
[With my apologies for the clunky google translation, here is the comment in garbled English.]
>>
Last Thursday with my 11 year old mare to the clinic for research. I suspected that the problems I experienced with her were in the legs. The diagnosis is surprising … Osteoarthritis
Patient record description:
Research Horse is poorly muscled in the top line. On hard running horse for quite short. Well right over the legs (not crippled, but crooked)
Sampling = – Hard fulls = – Well left bending. Lung on a soft reamer but the topline is too tight, especially the neck. Galop crosses over, especially to the right. Bend test RV +/- Other are-. Passive movements back possible, not painful. Neck caudal part not to move, both inactive and passive. Especially hampered to the right. Heavy blockages
C567 disorder right. Echo neck indicates C45 left fluid C56 L fluid (= v) and arthrosis (= a), C67L v, C7T1L v, C56 R
v + a, C 67 R v + a, C 7 T 1 R v + a. On X-ray side neck C45 +/- body
v + facet joints,
C56 +, C67 + (+ = enlarged facet joints with widened joint cleft). X-ray projection gives enlarged facet joints with reduction of intervertebral space at C45 L, C45 R +/-, C56 re and C67 re. Conclusion echo and X-ray lower part neck arthrosis with heaviness point C56, C67 especially right.
Since there is no lameness between clinical research, without saddle and driving, and the ride and / or saddle is also suspect. The lameness on the video can therefore come from the neck, back and / or saddle.
Advice:
-For the forefeet Toe shortening and on irons.
-Novacam 2 weeks 1x daily for 600 kg
-Neck is now injected C56.67 li + re with ultrasound guidance. Coming 2 days alone at the lunge. Then a small week with longer stays. Then to normal length of side. After 2 weeks there can also be started again with some driving after lunging (eg 2x per week 10 min). If this is not going well right away, the advice is to look at it with a bare-backpad. If that goes better, the saddle must be looked at.
If that does not go better, you also have to look at the back.
-Sowieso neck should not be cracked / manipulated. As a result, small pieces can break off and only irritate the joint. (I am also an osteopath and arthrosis is a contraindication to manipulation).
I have the mare only 4 months. I am looking for answers, possible therapy and experiences. I naturally wonder where this problem comes from. My first thoughts were wrong training (too much pressure) and / or possible trauma. I have so many questions … Can the animal live painlessly with the disorder ?, is therapy possible ?, there are gradations (from spleen to severe). Very happy that I found this site !! Very informative and instructive (also for my own work as a therapist).
Are you in touch with Equine Studies in the NL? Zefanja Vermeulen is working at the forefront of this issue, conducting dissections and research with Sharon May-Davis.
X-rays can be looked at, to inform you whether your mare has the congenital asymmetry underpinning the arthrosis.
Website here: https://www.equinestudies.nl/en/
Dank u wel voor de reactie. Morgen heb ik contact met Zefanja Vermeulen , ik ben erg benieuwd naar dit gesprek. Zelf ben ik NES therapeut (NES Equine performance system) ik werk voornamelijk met paarden. Ik heb al veel mooie dingen bereikt. Ik ben erg benieuwd hoe mijn merrie gaat reageren op gerichte behandelingen. Ik hou u hiervan op de hoogte.
I find this page very informative I’m so glad I have found it, I am training to be a human chiropractor and I work as a human sports massage therapist, my Dressage Hanoverian mare has been diagnosed with OA of C6/C7 and T1 she is only 8 she has been showing symptoms since the age of 5 (I’ve owned her since 2.5 years of age) I’ve pretty much had to work this out for my self as the signs were initially very subtle however it became much clear to me when the neurological signs and PSD lameness presented together. She has been steroid injected into the neck which worked and corrected 2/5 neurolgic and has been operated on both hinds for the PSD, I’m now bringing her back into work with vetinary advice, however I’m struggling emotionally with this as I’m not sure I should continue riding her any advice would be helpful
Very good article. I have a TB mare, clearopportunity if the pedigree helps, who does two very interesting things that I wonder if they could be related to C6 C7 issues:
1. When I lean forward to dismount, she squeals as if she was in pain. She is basically retired and is only trail ridden at walk so I’m not too concerned about the occasional trip on a rock and she does not show any sign of pain at walk but I wonder if the additional pressure on her withers could be a symptom of C6 C7 issue.
2. When she rolls, she takes forever to come down, her legs shaking and she looks like she is using her credit card to pay for car repairs: Not happy. Could this also be a symptom?
I’m just sharing these two things she does in case other owners with proven C6 C7 issues are seeing the same things with their horses. We can’t all afford the x-rays but if these are possible symptoms, it might help point owners in the right direction.
PS – I would really like to breed this mare one day. She is big boned and very athletic. I might just throw her at an Appaloosa stud or at a Lusitano!
Please- why would you want to pass on this unhappy mare’s obviously faulty genes & discomfort to a foal? If she has such difficulty rolling, how will she be with a foal’s weight inside? And another unwitting owner stuck with a potentially unsound horse? Have you tried riding her bareback to see if the saddle is the problem – as it often the case with wither-sensitive horses?
Is there any link to Head shaking syndrome? We have a tb gelding we have been working with for 4 years (no falling over) but he strikes out with his forelegs, and shakes his head severely and looks very odd under saddle, not lame just not quite right, we have had body work done by both a chiro and a bowen therapist but no improvement but as yet have not had any xrays done (cannot remember if he has one foot forward at grazing), Norther Dancer bloodlines mainly. thanks
I had a mare with Northern Dancer on the bottom. However, she had contracted EPM while in the care of a trainer that went unnoticed for quite some time. Needless to say, I pulled her immediately on a welfare check and aggressively treated her. She got somewhat better, but never returned to herself. On prior welfare checks, like you said, she was never “quite right”, and I couldn’t pinpoint any particular cause. After pulling and treating her for EPM, bloodwork showed she was on the high-end of selenium, and the lower end of vitamin E. Reading that vitamin E can aid with neuro problems, I gave her a recommended dose of E. I syringed it because she would not eat it, and about 5 minutes later she was thrashing, violently shaking her head, and was in a total panic. She was also striking out and rubbing her head on the stall wall. It was so violent, that it took two of us to get into the stall to hold her and sedate her. It was nothing like I’d ever seen before, and I am glad I had a witness. Out of curiosity, several days later I gave her a smaller dose, and she reacted again but not to the same degree. I was going to recreate it for my vet, but prior to do doing so, she fell on the ice, fractured her hip, and was subsequently euthanized. I realize my experience seems very crazy and not possible, but it was very real. Have you tested for EPM?
So interesting (and sad). I am curious, the instability issues described seem always in front. But don’t the lower cervicals have a lot to do with hind end control and proprioception? I have an adored and retired now Dutch /Tb cross, all the major TB lines Nasrullah etc. she has displayed an odd hind end stance for probably 10 years which eventually will likely be her demise. She has stood straddled behind, especially when eating, and a year or so ago the vet pronounced her ataxic but not dangerous to herself or others- yet. Could this be part of that issue as well?
Equine Congenital Vertebral Malformation (ECVM), as the C6-C7 issue is now being termed, can certainly lead to hind limb ataxia and proprioceptive deficits, and there’s a crossover with Wobbler syndrome due to restriction on the vertebral canal. Proliferative arthritis in the lower cervical vertebrae can increase the negative effects from around 10 years (if the problems haven’t started earlier, as they do in more severe cases). So it’s certainly one to add to your list, given that there are other causes of ataxia too. Hopefully it’s not going to become a worsening issue for your girl in her retirement – it sounds as if she has a lovely home.
After running my small equestrian business for a few years, our number of school horses expanded. In the last two years I’ve screened three of my horses for ecvm. Two have been positive. The other had different cervical arthritic changes which was treatable with cartrophen.
Both positive horses were under ten and we caught early symptoms. One was recently dissected by dr Christine gee, and the other is being euthanised tomorrow. The first was a little brumby which displayed unpredictable nervousness, and a very poor immune system. Ulcer prone. He went from being a quiet little fellow, to then bolting at the drop of a hat. He was pulled from our riding school.
The other is a young thoroughbred I was given as a project, to rehab and rehome. He started ok, but He was chronically collicky and ulcery. He then began to rear and get nervous sporadically. He colicked and panicked so badly he fell and fractured his skull. When he arrived he was easily handled and loved by all my staff, but in the last three months every single one of my staff has expressed that at some point theyve felt unsafe to handle him.
Neither displayed major neuro symptoms but showed other signs of severe stress. Diagnosing these horses has lost me income in both scenarios, but rider safety and horse welfare MUST come first.
Both of these horses had impeccable temperaments and tried their hardest, neither deserved this fate. Breeders MUST be aware of this. Thank you so much to dr Christine for her friendship and support in diagnosing these horses for me. Ensuring myself, my staff and my clients can remain safe.
I am working towards having all of my horses screened for ecvm, and I look forward to the day where this condition is more widely recognised, and then hopefully eliminated. Both of these young horses suffered tremendously and I cannot believe our luck that no one was injured.
For Bear and Arrow.
Thank you for posting this, Laura. I feel dreadful for your horses and mindful of the emotional toll this must take on you … at the same time, I am grateful that you found help and support in Christine.
I’m about to purchase a 7 year old, 17 hh WB horse. We have full radiographs (53) including the neck and spine. The area in question is C6 C7. I have had 4 Vets look at this area. The vet (international area) is excellent but he doesn’t see a problem. I hired another 3 Vets for a second opinion. One of the Vets is a Radiologist. They see a cyst and an oversized, irregular articulated facet. Would these findings lead to possible future problems? He is sound to all flexions and regains his balance easily in the neurologic exams. I have currently asked for another X-ray of C6, C7 with better placement. Please let me know if I can send you the radiograph in question or videos. Thank you
Emailing you privately with a contact.
2 yrs ago my AQHA cutting horse (Lena Little Smart) started short stepping in front and sticking his nose out and lowering neck at the trot. X-rays showed c6/c7 to be fused. Injections in that area made no difference.
Now I’ve bought a different AQHA cutting horse (Smarty’s Doctor). He’s been tripping, has fallen and stumbled with me and seems quite off. X-rays and ultrasound shows abnormalities in C5-C7. We’ve injected now between 5/6 and 6/7. Is it my bad luck, or do you think the (Smart Little Lena) lineage could be a root cause?
I knew something was wrong with my newly purchased and vetted horse, just discovered enlargement of c6 and c7 facet joint , reduction in size of intervertebral foramen. He also has bone remodeling of SI . I need help gaining the previous owners vetinary history, she is a breeder breeding horses into congenital pain , cheating purchasers that could potentially die froma riding accident
Does anybody have a contact for a vet in the UK that has experience of this??
I’m a farrier, a large percentage of my work is stud work and the “corrective side” of it….I’ve followed Sharon’s work for some years now, I see foals/youngstock that exhibit growth/postural problems (I usually get brought in to glue on various extensions etc)
When I suggest to vets that I work with that we investigate the possibility of ECVM…. I point out that it’s abnormal for a 9 month old foal to never lay down in its stable (often when they do they get cast) and you never see them roll in the fields etc- combined with the postural/development problems that I see I think there’s a case for further investigation, X rays etc, so I’m looking for suggestions for vets that have experience in this…
Thanks in advance
Wow this is the most informative article I have read about this condition, as well as the replies. I have currently found out that a broodmare I own has produced 2 foals with narrowing in the C6/C7.
Clearly this is hereditary in her case, and unfortunately will be the end of her career as a production mare.
Is there anyone out there who is gathering a database of lineages that have these abnormalities?
I also found it extremely interesting to hear that it has been found in 3rd term abortions. As this mare has had 1 3rd term abortion as well. Is this malformation thought to be a potential cause of a late term abortions? I really want to know more about that!!
I am sorry to hear about your mare.
On Facebook, try Equus-Soma re a genetic study: https://www.facebook.com/groups/846796842859723/
If you have radiographs, you can submit them along with a hair sample in the US.