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  Discussion on Mysterious hind-end lameness - possibly neurological
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New Member:
cekoz

Posted on Friday, Feb 9, 2007 - 8:20 pm:

My horse Doc has a lameness issue which my local Veterinary school has had great difficulty diagnosing. I was wondering if anyone else had any ideas about what he may have, keeping in mind that the symptoms may be atypical.

A little background on Doc: Doc is a 10 year old full-blooded QH (who looks somewhat thoroughbred-y). I have had him for about 6 years, and the *only* issue I've had with him is mild arthritis in his left hock which has been very manageable with injections. He has a capped hock on the right from before I acquired him, but since he has been in my care he has never had any lameness issues, illnesses, injuries, or traumatic experiences (insofar as I am aware of). He is regularly vaccinated and wormed by a DVM (who coincidentally is also the owner of the stables), as well as regularly seen by a farrier. He is stalled at night, and turned out in grass pasture with a herd for about 9 hours a day. He is also ridden several times a week and kept very fit.

In December Doc suddenly started to show a strange gait (literally overnight), where he would reach forward with his right hind leg in a slightly abbreviated way, flick his toe, and strike the ground very hard with the hoof. He was taken to the Iowa State University Vet School on December 15th, and was diagnosed almost immediately with a "textbook" fibrotic myopathy. He underwent a semitendinosis tenotomy that afternoon, and was sent home that evening. However, after his required 2 weeks of complete stall rest, it was obvious upon hand-walking him that the gait issue was not resolved, and if improved only minorly so. Also, he developed a very large seroma over the incision. After a week's worth of undersaddle work, during which the lameness was very obvious on the concrete but completely unnoticeable on the arena sand (at the walk and trot), Doc was given a day off, after which the lameness was more pronounced and noticeable in sand undersaddle (loud slapping at the walk, extremely uneven trot).

We took him back to the vet school, where upon trotting him on concrete it was noted that the condition had become bilateral (he was NOT trotted before on concrete, so whether this represented an actual progression or was simply not noticed before in unknown). Although worse in the right hind leg, both legs are obviously abnormal at the trot on concrete, and when trotting one gets the impression he is "cantering" in back, or hopping poles in back.

Possible PSSM (aka EPSM) was suspected, and a muscle biopsy was sent away to the University of Minnesota, which was returned normal across the board. Their next guess is some type of neurological condition, although they are not sure what. They do not believe it is stringhalt or EPM, although they do plan to do a spinal tap for EPM.

The whole time he has remained calm, alert, and with good attitude. He shows no signs of pain, backs up very well, and continues to eat, drink, and defecate normally. His only real symptom is the gait abnormality. He doesn't show any weakness, ataxia, tremors, muscle spasms, in coordination, etc, that I can see. He will often rest all his weight on his right hind leg (the more affected one, I assume because he is resting the leg with mild arthritis), and shows no obvious areas of pain or soreness. He will be going back to the school for a neurological exam (I believe
they said something like an "EMG"?), although I would like to have ideas when we go so there's less "stabbing in the dark". I respect the opinion of the vets I am working with greatly, however as they are somewhat stumped I would appreciate ANY and ALL input (don't make me beg!).

I have included a link to a video of him at the vet school, however keep in mind that as bad as he looks on the concrete, he looks almost totally sound at the walk and trot in sand.

Gait video link:
https://www.youtube.com/watch?v=VykzlTza9J0
New Member:
cekoz

Posted on Friday, Feb 9, 2007 - 8:28 pm:

The video was available before, but is not at the moment for some reason (I just uploaded it today, if that has anything to do with it). Hopefully, it will be resolved soon by YouTube, but if there is trouble viewing it please tell me, and I will find another way to post it. I feel it's important to see the video, as it shows his problem in a way I can't adequately put into words.
Member:
kthorse

Posted on Friday, Feb 9, 2007 - 8:46 pm:

The video was working fine. I hope you find some answers soon. Good luck with him.
Moderator:
DrO

Posted on Saturday, Feb 10, 2007 - 8:06 am:

Hello Christina,
If you will email me the video I will see it gets in the post so it is not lost. Be sure to put LAMENESS VIDEO in the subject line as we have trouble with too much spam.

I agree that EPM is unlikely, unless it has effected the peripheral nerves: a famous neurologist told me: CNS lesions (as are typical with EPM) create symptoms that are consistently inconsistent. He meant the gait of horses with CNS disease was altered but the way it was altered changes: it is consistently inconsistent. The regularity of the gait abnormality strongly suggest not a CNS disease.

Having watch the film 3 times I would describe the abnormalities as:
A shortened and hyperflexed anterior phase that is abruptly stopped and prior to planting the foot the posterior phase begins with the foot drawn rapidly backwards and down, splapping the ground. Occasionally the horse will stand and raise the foot several times as though trying to advance the leg but failing. The gait abnormality is apparent at the walk and trot and worsens at the trot but the character does not change.

Having watched the film 3 times and never once seeing the gait vary, the way the foot is pulled backwards and down, the obvious fight to advance the leg all lead me to think you still have fibrotic myopathy and they missed the muscle with the fibrosis or more than one muscle has the problem. This is a typical appearance for fibrotic myopathy and any other diagnosis would be quite atypical. Persistent muscles spasm or peripheral motor nerve dysfunction cannot be ruled out but I have never seen a case this regular and with these particular characteristics.
DrO
Member:
dres

Posted on Saturday, Feb 10, 2007 - 9:46 am:

Dr. O How does something like this happen??

Great video Christina, thanks for sharing your story , and I hope you get it resolved..

On the first day God created horses, on the second day he painted them with spots.
Moderator:
DrO

Posted on Saturday, Feb 10, 2007 - 10:24 am:

Ann you will find a article that explains how this problem occurs at, Diseases of Horses » Lameness » Muscle & Tendon Diseases » Fibrotic or Ossifying Myopathy & Myositis.
DrO
Member:
dres

Posted on Saturday, Feb 10, 2007 - 10:46 am:

Found it , thanks.. This looks so much like a friends mare that was kicked several years ago, the gait is not as pronouced as the above.. but when I was watching her walk.. I told the owner its like she does not know where the ground is?

On the first day God created horses, on the second day he painted them with spots..
New Member:
cekoz

Posted on Saturday, Feb 10, 2007 - 3:36 pm:

Dr. O,
Thank you so much for the quick reply! I appreciate your offer to save the video, and I will send that along to you shortly.

The vets at the school seem to feel quite strongly that it isn't a fibrotic myopathy (and, granted, they aren't infallible), but I was hoping you could clarify several points for me:

1. It appears that both his hind legs are acting abnormally at this point (more so at the trot), and as I understand it, because of the nature of a fibrotic myopathy it only affects the inured leg. Do you believe he is compensating on the other side, or possibly that the gait is so pronounced that it is effecting the way his entire hindquarters move? Or, possibly, that the cold or something else has aggravated his arthritis which makes both legs appear abnormal (the vets at the school do not feel this last one is a possibility).

2. He seems to be flexing his right hind leg (the affected leg) significantly MORE than the "normal" leg at this point (this did not used to be the case). I was under the impression that a fibrotic myopathy PREVENTED the flexion of the leg mechanically, but he is often showing greater rise and flexion in the affected leg. Also, although it is hard to see in the video, he is also showing a lengthened stride (that is, he tracks up better) in the affected leg, where I thought that a fibrotic myopathy would shorten the stride.

3. You mention the surgery possibly "missing the muscles", however I thought a fibrotic myopathy was scarring on the tendon, and an occifying myopathy affected the muscles. I could be mistaken, but could you clarify that point for me? Does it seem like perhaps it is an issue with the muscles instead of the tendon?
The vets did mention that there is another surgery for fibrotic myopathy aside form the semitendinosis tenotomy, one which had more complications. How do you feel about this surgery?

And lastly, what tests could I ask my vets to perform to verify if it is in fact a fibrotic myopathy? They are a vet school, and so have almost any testing device you could imagine at their disposal. Obviously, I would want a test which is quite conclusive as opposed to cheaper (for example, if ultrasound is the easiest but unable to penetrate significantly to identify the problem, I would be willing to opt for a more expensive, but more accurate, option).

Thank you so much for your time, and best regards,
Christina
New Member:
cekoz

Posted on Saturday, Feb 10, 2007 - 3:42 pm:

Dr. O:
I am having trouble finding your e-mail to send you the video.
Moderator:
DrO

Posted on Sunday, Feb 11, 2007 - 8:43 am:

Send it to horseadvice@horseadvice.com.
DrO
Moderator:
DrO

Posted on Sunday, Feb 11, 2007 - 8:59 am:

1) Yes I think the other leg may well behave abnormally because of the interrupted gait of the effected leg. Even if there is a lesser lameness in this leg, until you fix the major problem it will be hard to access.
2) The clinical signs depend on the particular muscle effected. If the muscle that opposed the almost stringhalt like flexion that your horse exhibits lost it's elasticity he would not flex like that. But that is not the case instead one of the muscles that must relax toward the very end of the anterior phase is as the leg is put down has lost its ability to relax.
2) Though the muscle belly is effected it is easier to cut the muscles attachment to the bone, the tendon, as it is smaller and less vascular.
3) I would have to know what surgery he is discussing and why discuss a particular surgery until the muscle is correctly identified?
4) The effected muscle belly must be identified and a decision made if there is a surgical intervention that has a chance of fixing it. Examination, palpation, ultrasound, and a good knowledge of anatomy would be the best tools for identifying the effected muscle, assuming my thoughts are correct.
DrO
New Member:
cekoz

Posted on Monday, Feb 12, 2007 - 5:29 pm:

Thank you again for a very informative response! It significantly helped my understanding of what a fibrotic myopathy is and how it might present.

I was just wondering if you could clarify in the last point (#4) any technological tests which could identify the problem, such as radiograph or x-ray, which could spot a fibrotic myopathy? Unfortunately, the vets have been unable to definitively palpate a location, and I worry that ultrasound may not penetrate deeply enough.

Also, I was wondering if you had any thoughts about it possibly being stringhalt? I have heard that mild stringhalt can be confused with fibrotic myopathy or PSSM (which they also suspected but disproved with a muscle biopsy), so I wonder if that is also an avenue I should investigate. His leg has significantly more flexion in the hock now than it did when the condition presented initially.

Thanks again!
Christina
Moderator:
DrO

Posted on Tuesday, Feb 13, 2007 - 10:03 am:

Radiographs are not as useful at spotting soft tissue lesions as ultrasound but there are some ultrasound units that can penetrate much deeper than others, it is a function of the wavelength of the ultrasound unit. Perhaps is the lesion has some ossification a radiograph might pick it up.

I have not seen a stringhalt that has the pulling back and down as he plants the foot that your gait exhibits however the hyperflexion is reminiscent of stringhalt.
DrO
Member:
cekoz

Posted on Tuesday, Feb 13, 2007 - 1:23 pm:

Ok, now I am confused again... isn't fibrotic myopathy (as I understand it now, thanks to you) scar tissue/calcification of the muscle, not lesions? Granted, I assume the scarring or occification often comes from an injury/lesion, but isn't the gait itself a symptom of the post-injury fibrotic/ossifying tissue?

Sorry, I will understand this all some day!
Moderator:
DrO

Posted on Wednesday, Feb 14, 2007 - 9:12 am:

Fibrosis is soft tissue, ossification may develop over a long period of fibrosis and probably related to repeated tearing of the fibrotic material, but is not a constant sign.
DrO
Member:
frances

Posted on Wednesday, Feb 14, 2007 - 10:54 am:

Hi Christina: I always thought the word "lesion" meant a wound, sore or ulcer, until one day I looked it up and discovered that any kind of unnatural difference from the norm in tissue formation is termed a lesion.

So scar tissue/calcification of the muscle IS in fact a lesion.
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