Well, good afternoon, everybody, and thank you for joining us. . We've had some very good talks this morning and I hope I can maintain that level of high standard and the momentum.
It's some pretty heavy going stuff I have to say, coming up in the radiology and myelography section, so please bear with me. We'll try to include some interesting pictures to keep you entertained. Just to begin with, I'd like to, add this disclaimer that, I am definitively not a neurologist or an internist.
I spend a lot of my time looking at lame and poorly performing horses. And doing surgery, rather than, evaluating, the nervous system in any great depth. So with that in mind, we'll, we'll go on to look at some of the reasons to image the equine, horses, the, the equine neck.
You can see here my wife is a, is a conservationist and a biologist, and, wherever we go on holidays, I'm always dragged around the, local wildlife parks and, so forth, to, to Take in the sights and you can see here is a bunch of flamingos demonstrating a very good cervical range of motion there, and I think those. Carrot flexions if we're performing them in a horse, I would be more than acceptable. So what are the indications for imaging the imaging the neck?
Certainly we think about the common neurological things like ataxia, hind limb weakness, and we'll talk a lot more about those as the talk continues. But we need to bear in mind that neck pain and other Performance limiting, clinical signs can be, caused by problems in the neck. So think about intermittent and unrelenting for limb lameness and obscure hind limb lameness.
Any horse that's performing poorly without a corresponding lameness, one that's been, where, where all of the common orthopaedic conditions such as proximal suspension desmitis, or hopcane stiffus, etc. Have been ruled out, really, we need to examine the axial skeleton, and part of that, of course, will include evaluation of the horse's neck. Proprioceptive loss, sometimes described by the riders as being heavy on the forehand or feeling disjointed between the fore and the hind limbs.
it's certainly an indication to evaluate the neck. Martinelli in his commentary, in Eve in 2010, reports that horses following successful, treatment of their articular facets of steroids are often reported as being less spooky. And in addition, the, the same author noted that of the 150 cases where he or she treated the cervical, facet joints, that only about 5% of these were for reasons of ataxia.
So we need to think about neck pain, we need to think about poor performance. And looking at the human orthopaedic practise. Very frequently with, cervical issues and other neck issues.
Some of the clinical signs or symptoms that are reported include weakness and pain in the appendages. And local restrictive movements. So we see some of the similar symptoms affecting people.
Again, I'm not a, neurologist, but, some of these cases, some of these cases presented to the orthopaedic service and you can see that some of them are mildly neurological and some of them are severely neurological. So for example, this first to. It's very weak, listening to the left side.
Demonstrating severe, severe neurological signs. This horse had, also demonstrated neurological signs. We tail pull, etc.
And the intern decided to try some of these, crossing reflexes. You can see this horse quite comfortable standing there with his legs crossed for an abnormally long period of time. So I certainly don't do that test in all horses, but it was useful on this occasion.
This is a poorly performing show jumping horse in the upper left, that we evaluated for neurological signs. And he steps on himself a few times behind, is not exhibiting classically that the very kind of unusual abduction behind, but is spinning on his forelimbs in a relatively unusual fashion there. And the lower left horse is demonstrating.
Quite marked. Quite marked neck pain as he lifts, as he flexes his neck there to to feed from the bucket, you can, you can see he's becoming agitated. As tailhead is elevated, he is demonstrating some ataxia as well.
Sort of a spastic weakness that we see with horses with compression of the spinal cord in the neck. This is a case you saw recently. Frequently horses with CSM, cervical stenotic myelopathy, when they're backing up their hind limbs can't keep up with their forelimbs and they'll lean back like this.
This is obviously quite an extreme case. And this is that same horse, circling. Sorry, the volume is on all these videos, circling, to the left you can see a very exaggerated hind limb abduction and just in coordination generally with the hind limbs and similar.
Signs were. Similar signs were noted on the other circle. So sort of In coordination.
And a and a spastic ataxia. This video I've taken from the internet, so apologies don't probably the right permissions to use it, but here you can see poor performance and potentially, cervical trauma in, in action. Just a brief word about ataxia.
So we're gonna talk a lot about cervical stenotic myelopathy, in the upcoming slides and for the rest of the talk. But it's important to recognise that there are other causes for ataxia and this, the proportion, of cases that you see will depend on your geographic location. But consider, these other differentials, when you're examining horses with spinal ataxia in the first instance.
So of course, EPM in certain parts of North America is very common. Equi herpes virus, degenerative myeloencephalopathy, various other congenital anomalies, which I don't have time to talk about in this presentation and trauma in the case report of one traumatic episode causing ataxia and a horse. So just cast a wide net initially, before, focusing on cervical stenotic myelopathy.
I'm gonna use that terminology for this talk. There are lots of other descriptions of what I, what is essentially the same disease. So we'll call it CSM for the purposes of This talk.
What's going on. Again, I'm not an internist or a neurologist, but we need to understand some of the basic neurophysiology. So CSM is essentially compression of the spinal cord due to narrowing of the vertical canal.
And that isn't a straightforward narrowing of the vertical canals we'll see in time. The clinical signs, that are related to both dysfunction of the upper motor neuron and the general proprioceptive tracts, and the clinical signs are seen in all four limbs. Upper motor neuron tracks, as you know, descend from higher centres and are responsible for regulation of muscle tone, to support the body against gravity, and to initiate voluntary movement of different muscles and parts of the body.
And their dysfunction results in a spastic form of paresis. And the spasticity arises from the fact that you have unchecked lower motor neurons, working on a reflex arc. General proprioceptive tracts are ascending and function to transmit sensory information about the position and movement of the muscles, tendons and joints to higher centres.
Ataxia due to loss of control of the position of the limb in space. So essentially, the horses don't know where their limbs are in space, and that results in ataxia. And also these proprioceptive defects result in an inability to coordinate voluntary movements accurately.
So you'll see in those videos, you could see the horses stepped on each other on themselves occasionally, and we're unaware of where their limbs were in space. Clinical signs seen with CSM are always a combination of deficits in both functional systems. So we get upper motor neuron and general propriceptive tracts affected, and we get this combination then of spasticparesis and ataxia.
So, CSM is A disease is spinal cord compression, and there are a number of types. And then there are a number of other that there's peripheral nerve compression as well that can occur with This developmental orthopaedic disease. So, CSM is a developmental orthopaedic disease.
And it's a disease complex, and this. Can manifest in, in two ways, really. In the young horses, we see type 1 CSM where the spinal cord is compressed, and we're going to understand a lot more about that when we look at some radiographs.
And in older horses, we can get spinal cord compression and again this is philtre through and the and all of the talk focusing on imaging as we go through. We'll see that in older horses, you get a secondary arthropathy and enlargement of the caudal facet that encroaches on the spinal cord, causing compression. We've talked about the clinical signs already with spinal cord compression.
So, with type 2 CSM. Or enlargement of the facets, we, we can see that the soft tissues associated with the joint and then Bone spurs, periarticular osteophytes that form with the arthropathy, can impinge on the peripheral nerves exiting the intervertebral foramen, and that can lead to forelimb lameness without spinal cord compression. So this is not a very, it's not a simple disease, .
And that is manifesting the difficulties that we have with diagnosing the disease. So I've mentioned that it's a developmental orthopaedic disease complex. And so what's going on?
Well, what do we mean by that? Well, the primary thing is a shortening of the vertical body, and that can, happen, at numerous different levels and results in subluxation of adjacent, virtual bodies. There can be a generalised and often is a generalised narrowing of the vertebral canal.
And then various manifestations of facet joint disease. So the correct name for these facet joints that we talk about in the neck are the, are the articular process joints. I think for the purposes of this talk, we'll just call them facets or facet joints.
So, for that joint disease, can range and can be seen in youngsters all the way through to older horses. So we can see various pathologies including OCD and with the case report, in the literature of an OCD fragment in a young horse that was causing CSM, and that's will be presented later. And also there are, we, we, we all know we find these regularly on X-ray, cystic lesions within the facet joints.
And with advanced imaging such as MRI we're finding that these are, we're finding these more frequently and we're finding evidence that this is part of a much bigger DOD complex. This is a horse that presented to Lee Hurst. It was neurological and we diagnosed CSM.
Obviously, he, he didn't survive to discharge and went to pathology. You can see, look at this video in action, you can see, . What we mean when we talk about dynamic and static lesions.
So from left to right, there's C2, 34 and 5, you can see between 4 and 5, that there's very substantial subluxation. Of the caudal vertebral body. As it tips up and compresses the spinal cord above.
It's also a little bit of. Luxation cranially. That may or may not be impinging on the spinal cord.
So this is very much that type one. Type one disease where we get subluxation of the vertical bodies, causing compression. So we think about how do we diagnose this disease.
Well, we've talked about how complicated the disease is and we're gonna see that as we go on. . So therefore, by definition, diagnosing it is going to be a challenge.
So the first question is, does the horse have CSM yes or no? And if it does, where does it have it? And those are two very different questions.
The latter question is important if we're going to embark on some stabilisation techniques, surgically to try to, Correct that subluxation. But we have to, in order to fix the problem, we have to know exactly where it is. So this is a real challenge, and it's a challenge because the disease is complicated, but the bony changes that we see are subtle, and there is an overlap in the population, both in terms of qualitative and quantitative measures between CSM horses and normal horses.
And that's further confounded by the fact that the maximum narrowing or the region that is narrowed most severely, is not always the site of compression. So we're gonna talk about some of these diagnostic imaging techniques. We'll start with radiology.
And predominantly we're going to focus on lateral lateral series from the occiput to T1. I think it's important to Hone your technique to achieve as Lateral or radiograph as is possible, and that will help with interpretation of, both the qualitative and quantitative measures that we'll talk about. So initially we'll look at the qualitative measures.
And things that we find in CSM. And you can see this, schematic is very representative of the pathology case that we saw at parasagittal section of the spine of that horse with CSM where you get obvious subluxation and the schematic here at C5 to C4 subluxating. With that, on radiograph, we'll see apparent extension of the vertical arch, and that's illustrated there on C4, there's an arrow through the through the roof of this the the the vertebral canal, and that extends, that seems to extend caudally.
You get dorsal projection of the caudal epiphysis, and again we saw this in, in that specimen, and this can be either dynamic or caused by fisitis in the region. And the other classical qualitative sign is arthropathy of the articular processes. And this can either result in CSM or can be a result of subluxation elsewhere.
We should understand that by the end of the talk. So these qualitative measures have poor diagnostic accuracy. So we'll look at some quantitative.
Measures, and many of you will have come across these measures from your, your own research and looking in, in, in books such as Butler and that, and they can be very confusing. This picture is taken from a paper by hand, and we'll talk a little bit more about that paper in the next couple of slides. But just to give you the nomenclature for these measurements, we've got the minimum sagittal diameter, and on this diagram, it's represented by the short green line, A.
Intra-vertical sagittal ratio, sometimes unhealthily called IVR. Are the two green lines divided? And that's beneficial over the minimum sagittal diameter as the vertical body will correct for magnification.
And also, the size of the horse. Invertible sagittal ratio. Is B divided by the vertical body depth, so B divided by the long green line.
So B and C should be selected for the intervertebral sagittal ratio and the shorter of the two lines is selected. So clearly we can see that B is shorter than C in the circumstance of B divided by the long green line will give you the intervertebral. So ratio.
So these have been described by a number of authors, and you'll see very frequently this slide and the next slide referenced when it comes to looking at the introvertible and introvertible ag ratios. So more at all in 94. How to find the normal.
Cut-off point for the intervertebral sagittal ratio and for C3 to C6, that's 52% and for C6 and 7, that is 56%. So these remember the intervertebral, so between the two vertebrae. And the sensitivity and specificity of this test was in and around 90%.
I think most clinicians would agree that that probably isn't the case. Looking at the minimum sagittal diameter. This author found that horses with CSM.
Had narrowed MSD values C3 to C6, regardless of the size of compression. This highlights that generalised stenosis is an important feature in the pathogenesis of CSM. Hahn is the other author that is frequently referenced.
When using inter and intra vertical sagittal ratios. In this study, they looked at 26 neurological horses, only 8 of which had CSM. And the breakdown of the number and the location of the lesions is listed there.
What's interesting is that all horses with cervical vertical malformation had at least one intra-vertical surgical diameter of less than 48.5%. I'll have a little look at how those ratios pan out in in real time on the next slide.
But if you look at Has results, we've got two tables. The top table is normal horses or horses without cervical vertical malformation or CSM as we're calling it, and table 2 below is the represents the intra and inter-vertical measures. For horses with CSM.
And if you cast your eye from C2 to C2 for normal so to speak, and, and CSM affected horses, you can see that the means are smaller. So we've got 7.2 to 6.3, 6.1 to 4.8, 5.9 to 4.8.
So they are narrower than normal horses, and then also that bears true both intra and intervertical. Measurements with 9.17, so on and so forth.
There's no clear cutoff, and that's the difficulty. We're not going to go through this in detail, so, please, don't worry, but just look at the solid black lines represents the the CSM horses and the dotted lines or dashed lines represent the measurements. Of the introvertible ratios for the non-CSM affected horses, and you can see that ratios are all significantly smaller for affected horses.
So where does that leave us? Let's have a little look at these measurements in action. So here's our.
In a study evaluating inter and intra-observer agreement for these various ratios, looked at a population of 27 horses, 20 of which had CSM, 7 of which were normal. And you can see when you look at the introvertible ratios, if you become more lenient on the ratios, so in other words, if you increase the value from 50 to 52%, C3 to C6, and from 52 to 56 for C7, you can see that you get a very different diagnostic accuracy. That is to say that the sensitivity and specificity change.
This illustrates beautifully the trade-off between sensitivity and specificity. And I've included a little cheat note there in the top right hand side of the page where you can see that. Sensitivity is the true positives divided by the true positives and the false negatives.
So sensitivity is in one sense, a measure of the false negatives. So as you increase the laxity of the test, You can see that you get less false negatives, and that follows. But the specificity drops as you become more lax with your ratios, and you can see that the specificity is really a measure in one sense of false positives, you know, as the specificity lowers the false positives increase.
So you can see that there is a big trade-off between the two, and for a very harsh cut-off, this as described by hand, you can see that sensitivity is extremely low, but the specificity is very high. This is important to understand these basic and Principles of diagnostic accuracy when interpreting results. Interestingly, this paper did detect that not only are the horses giving us a hard time with these measurements, but that we're also giving ourselves quite a hard time.
It was not particularly good intra or indeed inter-observer agreement, and this led to discrepancies in diagnosis and treatment. So really, all in all, I think these quantitative measures need to be interpreted with caution. Again, looking at another population of horses where various measurements were recorded both quantitative and qualitative, we can see that the agreement with the gold standard of crops, necropsy is.
Below a standard where we would all feel comfortable, I think. So we can see that . The 16 6 horses of the total population, 239 that underwent radiographic examination.
16 had CSM, were diagnosed with CSM and went for postmortem. And when they looked at the Introvertible ratios for these horses, very unhealthfully there and labelled as IVR, but it is intravertible ratio. Using the parameters of 50% and 52%, sensitivity specificity were only 50% and 70% respectively.
So again, very equivocal results for the quantitative data. Look at the qualitative data then, so on their radiographs, they defined articular process osteophytosis and 98 horses that only agreed with necropsy 66% of the time, and vertical column subluxation. In 61 horses only agreed 56% of the time.
So this equivocal diagnostic testing led one author, and Aaron Stick, the equine surgery book to develop this decision tree. Yeah, I'm conscious that this is quite heavy going, so we're gonna move on through that and and look at myelography. Just a little word on the technique for those of you who aren't familiar with myelography under general anaesthesia, the cisterna magna is punctured via the atlanto-occipital space.
Obviously, aseptically, CSF is withdrawn from the subarachnoid space, and contrast is injected. The horse's head is then elevated. And you can see that represented very nicely in this picture that I've taken from Van Bierlier at A 2006.
So, the horse's head is elevated, that encourages flow of contrast caudally, and then the horse is X-rayed, lateral radiographs are taken in both flexion and flex and neutral positions. So that's essentially the myelogram technique. The interpretation gets extremely complicated.
There are I'd list 4 of them here, 4 different parameters to define the diagnosis, and many of those are disputed. Myelography also determines whether a lesion is dynamic or static. Static if the Static if there is compression diagnosed with a neutral head position and dynamic if there is compression only noted when the horse's head is inflexion and inflexion typically is when the horse's head is put between his carpi.
Just to list them briefly, we're looking for over 50% decrease in the sagittal diameter of the dorsal and ventral columns, and you'll know that some authors recommend over 70% decrease. And those columns are listed the dorsal column is the slightly pinkish purplish colour, vertical lines through the blue, subarachnoid space there, that's the dorsal myelographic column, and then you can see the little pink line that measures. The sagittal diameter of the doors so.
Contrast column. Again, various authors advocate using 20% or indeed over 20% reduction in the dural diameter. The dural diameter is denoted by the green line.
And then a variant on this is the dural height ratio where you divide the two green lines of the green line there at the intervertible space and then mid vertible body. And the dorsal contrast column of less than 2 mils, that's often quoted and that is largely defunct. We don't tend to use that anymore.
This is the most comprehensive study that I'm aware of evaluating the diagnostic accuracy of myelography, and I won't go through all of these, but basically, they had 38 horses, half of which had CSM undergoing myelography, and they tried to use, they used investigated, numerous different measurement techniques to establish which was the best. And sadly, no single criterion is highly sensitive and specific with the exception of C6 to C7. Where a 20% reduction in the door in the, dural diameter was highly sensitive and specific.
Mid cervical region is the most challenging and Can become confounded by flexion and extension. Certainly, the, these authors report that myelography is not always reliable for sight compression. So you can read through that slide on your own time, but essentially, myelography with radiography doesn't seem to be the answer for these mid cervical ones at least.
What kind of complications, can we see prolonged recovery from anaesthesia, seizures, and cortical blindness, non-sup meningitis. Associated fever, all quite scary, and thankfully most self-limiting. I think we also have to consider the, the Recovery from anaesthesia and an a toxic course.
So let's look at some myelography in action. Again, Levine naval, this is the paper where they looked at lots of 270 CSM cases, and we've seen already the diagnostic accuracy of their radiographic, qualitative and quantitative measures, and now we see the myelographic results. So 134 horses underwent myelography, and 68 of these.
Had knee cropy. So, mostly, most frequently detected lesion in myelography, vertical canal stenosis. Reasonably good sensitivity and specificity, 71 and 65, vertical column subluxation reasonably good there at 85 and 75% sensitivity and specificity.
And so on. So myelography certainly outperforms radiography, plain radiography, but it's still a long way off being a gold standard. OK, that's the really heavy going stuff over and now we'll move on to centigray with a little wallaby here who's also demonstrating some quite excellent cervical lateral flexions.
Any of you interested in centigraphy, actually check out this paper, a study by Quinyetta 2017, that looked at 468 horses that had undergone centigraphy for lameness and poor performance. These are not suspected fractures, these are adult courses undergoing an evaluation for poor performance. 64 of these horses had cervical centigraphy, and the results are listed here, and we'll just look at the sensitivity specificity and how that will play into helping us in the clinical setting.
So we can see that Positive centigraphy of a vertical body or facet joint. And this is looking not specifically at CSM you have to understand this is looking for the, the full breadth of the disease complex, possibly peripheral neuropathy, low, poor performance resulting from low grade neck pain from osteoarthritis in the facet joints, potentially fractured facet joints, that kind of thing. It's a little bit broader than CSM alone.
The positive centigraphy, that was only correct half of the time. And negative centigraphy, but on the other hand, negative centigraphy is likely to be negative for disease. So if you see a positive, it's only going to be right half the time.
If you see increased rate of pharmaceutical uptake, you're right half of the time. And if you don't see it. You are unlikely to find disease at that location.
So it's very useful information there, from that, from that study. And for those of you interested, as I've said, in stantigraphy, a lot of other of other common areas of orthopaedic pain, proximal suspensaries, lower hocks, etc. And are detailed in that study.
This is just a centigraphy of a pelvis ongoing. Again, just to give you some information, about centigraphy, 10 mega Becres per kilogramme body weight of 99 technetium methylene diphosphonate is what's typically used. And just to give you an idea of what's going on there, the uptake of radiopharmaceuticals in bone is due to physical physicochemical absorption into the crystalline structure of hydroxy appetite.
Deposition of radiopharmaceuticals occurs at sites of mineralization. In association with osteoblastic activity. So it's not present in the present, it's not present where osteoclasts are busy working, so for fractures and numbers of weeks before the osteoblasts start to do their job before you're going to get an increased rate of pharmaceutical uptake.
From, a study by Martinelli, some practical tips just on centigraphy, but it's a good idea if you're seeing increased rate of pharmaceutical uptake at C4 C5 or indeed C5 C6 compared to C6, C7, and if, and if it's significantly if C6, C7 is significantly quieter, well then pay more attention to C4, C5, or C5 C6 and if they're hot. And just bear in mind that with true CSM, so generalised vertical canal narrowing. It's very unlikely that we'll see any increased radiopharmaceutical uptakes uptake because there's no osteoblastic activity.
So that follows. CT, we've already heard lots about CT this morning. Alison, and Justine, both, spoke very eloquently about CT.
We're gonna use it, in this circumstance to have a little look at, A little better look at CSM and try and give us a better understanding of what we're looking at on plain radiographic myelography. A long time ago, 1992, this paper was published way ahead of its time by Moore. And funny enough, this is still, as far as I'm aware, the only CT myelography paper that's currently in the equine, in literature.
They looked at 9 horses, 6 of them were neurological, suspected CSM horses, and 3 were normal controls. The criteria, the diagnostic criteria that they used for Determining their diagnosis, sorry, I should have mentioned that these horses all underwent radiographic, so X-ray myelogram first were then put down and then they had CT myelograms performed, and they call their CT myelogram contrast enhanced CT, so CECT it's called in this paper. And then the horses were euthanized and they performed histopathology to again, using histopathology as the gold standard to compare the the diagnostic accuracy of myelography and CECT as they call it.
OK, so for their myelograms, the plain X-ray myelograms, attenuation of both dorsal and ventral contrast columns by over 50% of opposite sides. And this was used as dynamic and this determined whether they were CSM sufferers or not, and then they looked at whether there was Whether it was static or dynamic, depends on the changes that they saw with this parameter, the dorsum ventral ventral contrast columns. During flexion or indeed extension.
OK, so that's just a plain one. The CTs were performed with the heads in neutral position. That's important, and that's something that we've noted here in Leehurst with our CT machine that once the horse is in the position, there is no way we can perform flexed views, not, not even anything close to flexion to the knees, but not even partial reflection realistically.
And that doesn't seem to be a problem as is evidenced in this paper. So we'll look at some of their results. So of these 6 neurological horses, 10 compressive lesions were identified in histopathology.
Looking at the results, myelography identified all 10, as did. CT myelography. But the X-ray myelography detected two false puzzles, and this is where they were using the minimum sagittal diameter of 18 millimetres, which was published around about this time.
In the early 90s and Probably this is an unfair measure in horses. CECT identified all 10 sites have said with one false positive and in table 1 there from taken from their paper. More out.
You can see that the myelography lesions are defined as dynamic or static. And it's interesting to see how they then relate, the dynamic and static lesions relate to the CT myelograms. We'll talk about that in this slide.
So there were 8 dynamic lesions identified, and that was determined, remember from the radiographic myelograms. So 5 of these dynamic lesions demonstrated circumferential compression of the dural sac. And that was determined by this CT myelogram in the upper left hand side of the the picture in the upper left hand corner shows there's very little contrast agent there in the subarachnoid space.
This is a circumferential compression. The other three dynamic lesions didn't show circumferential. Compression, but did show lateral compression or lateral impingement of the dal sac, by a malformed or diseased articular facets.
You can see in the upper right hand corner of the slide, the white arrow there is pointing to an area of contrast attenuation. There's no contrast in that region. It's being squashed by both the soft and bony tissues of this enlarged diseased articular facet, and that's causing And that that would be what we would call a type 2 CSM as defined by, as defined at the beginning of this talk.
Two static impressive lesions demonstrated circumferential loss of contrast, and we'd expect that. They're evident when the head is in neutral position on on myelogram. The other really interesting information that came out of this paper was that they could detect compression of the nerve roots by malformed or diseased articular facets at 3 different sites.
In the lower right-hand side of the picture, I have a transverse section, from one of our clinical cases here, it's a plain. CT, so no, myelography being performed. But you can see with these diseased facet joints, there's a large osteophyte affecting both the left and the right hand side, and it's impinging.
Eventually, towards the intervertebral foramen in that region where the the nerve root is present. OK, very large osteophytes present there. And this is one of the benefits of CT.
We get much better definition of the lesion compared to radiographic myelography. So, in the discussion from this paper, they described that CT provides spatial orientation of complex anatomical structures without overlap. Well, I think you've heard lots about that particular point all morning.
In humans, they prefer CT myelography or X-ray myelography. And we, as I've already alluded to, we identify both dynamic and static lesions. Even with the head in a neutral position, and the additional benefit is we can identify peripheral nerve roots.
That are being impinged upon or encroached on. By diseased facet joints. OK, so I'm conscious of time.
We're still trolling through a lot of diagnostics here. MRI, there are two papers in the literature. MRI for a number of reasons is unlikely, but certainly in the UK, but I, I, I stand to be corrected elsewhere worldwide, but in the UK it is unlikely to be used widely.
In the immediate future for er for cervical evaluation. One is the time of acquisition is too slow, which you've probably heard about this morning already. And two, the boar size tends to be limited to increase the signal strength.
So fitting a horse's neck in, particularly the lower neck is likely to be impossible, and you can see in these, figures taken from this paper by James and that these have been dissect these specimens have been dissected fairly substantially, prior to MRI. But the beauty of this and the another study which I'm going to skip for today, is that we find that we can use their findings and Use those in CT myelography and draw comparisons between the two imaging techniques. So to make that a little bit clearer, we'll look at some of the measurements that they took in this paper.
So, as illustrated across the top of the, the top of the slide there, they could do various area measurements from these transverse sections through the cervical spine. And the important ones were the canal area and the canal, sorry, the cord canal area ratio, and that's the 2nd and 4th pictures across the top of the slide there as a ratio. So looking at the cord and the overall canal, and those are two measurements that can easily be made with contrast, with the contrast myelography using CT.
And the authors concluded that canal area and cord canal area ratio. Are more accurate than the standard introvertible and other qualitative measures, or quantitative measures, excuse me, that we discussed earlier in the talk. So I think that's something that we can transfer to the CT to improve our diagnostic accuracy of CT.
OK. Ultrasonography, there's not a lot to mention here. There are no, there's no real original research evaluating, the benefits of ultrasound, but we all know that it is useful for looking at joints, periarticular osteophytosis, siopathies, joint capsule.
Thickening, etc. And, ultrasound comes into its own fairly well, for guiding needles for treatment and . Also has been used to guide endoscopic approach to the facet joints for endoscopic or arthroscopic evaluation of the joints.
So Olshan is useful, . And we'll see why in a in a moment. As a subset of CSM and neck pathology, I thought we'd focus on facet joints for a moment or two.
We've already highlighted a lot of the important factors, when discussing facet joints and their and their important role in the CSMDOD complex, both for spinal nerve root compression and also reduced performance. So those points are illustrated by Mitchell Adal 2011 there. And horses with, and again this is something that we've seen already, horses with CSM were more likely to have Fat OA and controlled horses.
Or other neurological horses. So there is a chicken and an egg scenario here with a with a subluxating vertical body, you're going to have subluxation of the facet joints as well, and that's going to apply abnormal load to those facets. So that may be one of the ideologies behind older horses developing OA of their facet joints, is that that horse may already have suffered from a subclinical.
Instability in the vertical column resulting in OA set joints. And then we know that as part of the DOD complex, even in young horses, there can be, there can be facet joint disease. In a retrospective study by Dan and Hen in 2009, they looked at the cervical radiographs of 122 horses, and this paper isn't terribly insightful in that they didn't find any clinical significance.
But one thing that did come out of the paper, I thought, was certainly a very nice way of looking at the set joints on plane radiographs and evaluating, subjectively. Whether there's enlargement of the facet or not, and I'll just fly through the next sort of couple of slides demonstrating the various grading schemes they had. Now bear in mind the grading scheme wasn't really validated in their paper, but I just thought there are some nice examples of pathology.
in their grading scheme, and I thought that that was, quite a nice, take home message from this paper that we can look at the sets in a number of different ways, new bone dorsal to the joint and new bone ventral to the joint, . And for those of you who aren't that familiar with looking at facet joints, it's a really nice, it gives a really nice illustrative examples of various degrees of facet joint disease. David, just but in there just to let you know there's 10 minutes to go, that's all before the morning session ends.
That's all. OK, lovely. I'll have to fly.
Thank you. Yeah, OK. I've talked about the joints, .
As part of the DOD complex, and here you can see these are young horses with CSM, and they've got various, arthropathies or various disease of the joint or sclerosis and imaginations. Subchondral bone plate. At one point in this is that face lesion.
Facet lesions diagnosed on MRI occurred with increased frequency. And severity in CSM horses. So this just ties the whole lot in together that the facet joints are, are clearly a part of the disease complex.
Very nice paper by Withersidal describing the this radiographic projection, the oblique radiographic projection to look at cervical vertebrae. I'll leave you, these are all, all of these references are listed at the end of the talk. The take home message for there is that Where the from C4 to C7, an angle of 50 degrees should suffice for taking that oblique X-ray, and 50 degrees is, is when you're taking them from a practical perspective, is significantly bigger angle than you think.
Most of the time when we don't take them and we don't get good enough quality images here, it's because we haven't taken enough of an angle. OK. OK.
I'd like to talk a little bit about treatment. We've been focused mostly on, mostly on diagnosis to date. OK, so Birmingham Adal is one of the only papers that describes the results of or the outcomes following steroid injection of set joints.
The indications in this paper for injections were quite wide, so anything from lameness to neurological deficits. And they're listed here, that 124 horses injected the facet joints with corticosteroids. 59 were available for follow-up, and you can see stiff neck, taxi, obscure limbs, decrease performance.
And we've talked about the importance of evaluating the neck with all of those kinds of clinical signs. I think this is pretty positive. 70% of these horses returned to normal function or improved, and the improvement ranged from 25% to 75%.
But in the majority of horses, you're going to expect some improvement, and in some horses, the improvement was long lived. So I think, this is one of the few scientific validations of facet joint injection, in a clinical setting, and I think it's, to be commended. OK, looking at a, an investigation that I was part of with my colleague, Jessica Johnson, we looked at devising a really practical way to treat these facet joints in the field because we wanted to move away from specialised transducers like microconvex.
So we, we, we compared a number of different needle gauges, a number of different transducer types, and a couple of different approaches to the facet to the facet joint. Looking to, really validate, an easier approach to medicating the, the equine neck. In this video, you can see this is the dorsal approach.
The needle is coming from the right-hand side, engaging the very narrow joint space. And at the very beginning of that video, it's evident that there's a little bit of fluid flooding under the, the joint capsule there as the injection is made. And you can see from the, the transverse CT image on the bottom that that needle with a dorsal approach is targeting, and this is an approach that's been described numerous times.
I find it quite challenging because that target is so small between the facet joints. So we looked at the cranio dorsal approach. We felt that that would give us a much wider target and again the transverse CT image here, you can see that the space between the two facets is much wider, and that pans out.
When you're injecting them, you can see that the joint space is much wider, and that needle is right between those joints for that injection. So personally, this is the way I inject them now, I find it substantially more straightforward to do it. Although in this study, we didn't find significant difference between either dorsal or cranial dorsal approach.
So to get the right angle, and look at the the picture in the lower left hand side of the of the screen here, we can see that the yellow line indicates the dorsal approach, perpendicular to the spine and the green line and is a is a 45 degree. Counterclockwise rotation of the transducer and that allows access and you slide towards the front of the facade and that allows access to this wide area of the joint. Overall, our accuracy was just shy of 90%, and the previously reported success was 72%.
So we felt that that was a fairly good improvement. It wasn't all down to the operators, I can assure you of the technique. I think a lot of it comes from the improved ultrasound technology that we have available to us, .
And the the improved visualisation and I, and I suppose the training nowadays, and we're all getting better at at ultrasound guidance. So we injected these cadavers with a contrast agent and then CT them. It's a sort of a CT sort of day today, so I thought I'd show you that picture.
Sorry, it's not outside, it's the way the videos come out. So as we roll from cranial to caudal, you can see the contrast agent is pretty well within the facet joints in most of these forces. Little bit leaks out and we graded them according to the the degree of leakage and whether we missed or not.
And we felt that the that would give a a a better representation of the success of the injections. So Our take home messages from that was very easy to learn to do the technique, and that high levels of accuracy could be achieved, using either linear or microconvex transducers. Most of us have linear transducers, in, in our cars on the road, so I think that is useful to know.
Some risks. I, I see it more as an advantage rather than a risk. Some of these slides were put together by my colleague and and I felt that.
In, in the middle picture here, you can see that the nerve has been grasped with the forceps. This is the nerve exiting the intervertebral frame and you can see it stained with methylene blue. .
Tells me two things. One, I don't necessarily want to inject those facet joints with local anaesthetic for fear of inadvertent anaesthesia of some of these big cervical nerves. But also if the nerve is being impinged on and is slightly inflamed, then putting a therapeutic in the joint may benefit that nerve, by local diffusion.
Arthroscopy has been described as I mentioned earlier, by PEEA 2014 and then was used in the case report in a in a a 3 month old. I just put my notes up, bear with me, sorry, and a 3 month old, full demonstrating neurological disease. It's a very nice, very nice case report.
Sadly, the, this, the fragment was successfully removed, this OCD fragment in this in this youngster, but then, sometime 4 weeks after surgery. So 6 weeks post-surgery, apologies, the horse was found recumbent, and the diagnosis of CSM was made, but that would fit with our current, . DOG complex kind of stra strategic investigation of these conditions that, this, this horse may well have had a generalised narrowing of the vertebral canal and the inflammation that followed surgery and indeed maybe the additional instability that followed surgery after removal of this fragment led to worsening of clinical signs, and we sort of touched on how we've seen that in human patients and And also in our equine patients.
Endoscopy has also been described. I'll just show you some, some, very cool pictures by prying at Al. These authors performed 3, a series of 3 experiments.
They started off with cadavers, and then healthy mature horses, and then I've done a couple of clinical cases, where they pass a flexible, 4.9. Millimetre diameter endoscope into either the epidural space or the subarachnoid spaces really, really cool stuff.
And they're able to evaluate the durama, the nerve roots, the blood vessels, spinal cord blood vessels, arachnoid tuberculations, nerve roots, and external branch accessory nerve, depending on which space they enter. And here are some pictures from that. This is a myeloscopic picture.
This is an epidoscopic picture. And I would recommend any of you interested in the anatomy or pathology of this area to look at these papers and these pictures to find out the the Find out what you're looking at. This is a clinical case, and this horse has got narrowing vertical stenotic myelopathy, and you can see the left side is at level C5, C6, the right side where he had narrowing is C6C7 on the right hand side is substantially narrowing with the dorsal roof of the, the dura being compressed onto the spinal cord.
OK, so really, really neat stuff. A little bit more on treatment, Reardon. Colleagues in 2010 evaluated the biomechanical, various biomechanical properties of the traditional curve cutter and then the more modern, I suppose, locking compression plate, and they evaluated.
Stiffness moment to yield and failure moment of of these two constructs. So the the curve cutting cylinder and the LCP as I said, and their results showed that the LCP was substantially stronger in, in, in all circumstances. Then performed .
The surgery on a real life case, a 3 month old foal with a taxi and CSM, they've called it CVM at C6, C7. Again, remember, they've probably gone for the surgery on this one because they had very much, very, you know, we're confident in their diagnosis post-myelogram because C6, C7 is one of those sites where we can be confident. The Philly recovered well.
They did, they did have to replace the screws. It's a minor technical thing that's beyond the, beyond today's talk, but the filly went on, recovered well, and 30 months later, had improved by 2.5 neurological grades.
And one of the mechanisms for the proposed mechanisms for the improvement of these forces, post-surgery is that the enlarged facet joints that have, been diseased, once the virtual body is stabilised, 2, you don't have one, you don't have ongoing trauma to the spinal cord by the luxating vertebral body, but 2, the facet that was enlarged and diseased remodels and becomes smaller, so you actually get an enlarging of enlargement of the vertebral canal. I'll end with a case that we saw here at Lee hear some or I have a minute left. This horse is an 11 year old sport horse and the case was given to me by Alison Talbot, who you heard speak earlier on today, so thanks to her.
Abnormal head card one written bilateral foot lameness. Abolished by abaxial sesamoidian nerve block at a low grade right hand lameness. But there's this head, position and head carriage the owner was unhappy about.
And here you can see the two, these are composites I've I've pushed these pictures together, composite scytograms, both of the left and right cervical neck. And one thing we learned earlier was that if C5, C6, It is hot, and C6, C7 is not hot to pay attention to it. And on this horse's right.
Cervical centigraphy, we can see that C5, C6 is hot and C6, C7 is not. So that is significantly that is significant and warranted X-ray. Here are the lateral X-rays, lateral lateral x-rays of the horse's cervical spine.
And then the inserted view there is a close up of the C6 C5 C6 articulation. On the oblique views, you can see that there is a fracture of the Dors articular process on the right side. Correlating with the finding on the antigraphy.
OK. In summary, I'll wrap up. Consider cervical pathology in poor performance cases, and not just those neurological cases.
CSM is a developmental orthopaedic disease complex with numerous different pathologies. Recognise the limitations of radiography for CSM. And indeed myelography for CSM.
But that horses, if they've got a tendency to have lower intra and introvert ratios, they may well be positive for CSN, compared to their compared to normal horses. Add oblique radiographs, to your radiographic protocol to evaluate facet to evaluate for facet OA and OCD. CT myelography is likely to become the gold standard.
And when injecting, I would advise using a cranio dorsal ultrasound guided approach to medicate the facet joints. And with that, I'll wrap up the talk. Thank you all for your attention.
Great, thank you very much, David. Really, really, interesting talk, bringing it all together. What can actually be quite challenging cases, I imagine, to, to work up.
And another good example I guess of how advances in CT with use of CT malography, how that will hopefully improve diagnosis in these cases. Indeed, indeed. Apologies is a little bit whistle stop, but it's a, it's a vast topic and I, I hope you and the, other, delegates were able to, to follow through the various radiographic parameters and myelographic parameters.
It's quite, yeah, yeah, it's really clear and it's nice to have the image and everything to back up, what what you were saying in the and also all the text and the references and things so. So unfortunately, that is now the end of this morning's stream. I would like to thank, the team at the University of Liverpool.
So, Professor Deborah Archer, Justine Kane Smith, Alison Talbot, and, David Stack, we've just heard, for their, really fantastic talks, kind of covering imaging of the head of the neck, and also, just in going into more detail on how to use that for dental disease as well. So, thanks to all, our speakers and, and thanks to everyone for listening.