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EQUINE HEALTH
“In my experience this syndrome is much more common in older horses than it is in young One potential cause, and more on the neurologic side, is arthritis in horses. It’s usually seen in horses that are in their late teens or in their 20’s or older.” the vertebral column in the back region.
cause of the side-walking may be neurologic or musculoskeletal. I have seen more cases that are due to neurologic, spinal cord problems, but have also seen a fair number that are due to musculoskeletal problems. In that situation it usually involves the pelvis or the hind legs. Things like pelvic fractures or hip arthritis can cause this odd gait.”
This is much more common in older horses. “When younger horses suffer a pelvic fracture, they don’t do this as much. Sometimes we wonder whether the fracture in an older horse is cause or effect. Perhaps they have fallen because they have this abnormal gait and fracture the pelvis because they fell. Or did they break the pelvis and then it causes them to walk like this? It can be tricky to figure out sometimes,” she says.
“The other thing I have seen, as a poten- tial cause, and more on the neurologic side, is arthritis in the vertebral column in the back region. Thoracolumbar arthritis, or interver- tebral disk degeneration may be at the root of this,” says Johnson.
“It’s almost like a degenerative back arthritis or bulging disks in a person. I sometimes make that comparison to explain to clients; this problem in the horse is somewhat like a person who has a bad back. That person wakes up
one morning with severe muscle spasms when they get out of bed, and maybe they just slept wrong, in a position that causes a problem. Then they walk around all day kind of crooked to one side. Maybe this situation in horses is somewhat similar,” she says.
“One of the things that I feel is really mysteri- ous about sidewinders is that it can come and go, to a certain extent. I’ve seen horses that developed this syndrome acutely; they are suddenly walking with their hind end drifting to the left consis-
tently and the gait stays like that for a while. Then they seem to improve and can recover almost back to normal for a period of time and then the abnormal gait may return,” she says.
When it comes back, sometimes the hind end is drifting to the same direction as it did before, and sometimes it swaps. “Where they were cocked to the left the first time, they are now cocked to the right. This is very confus- ing from a neurologic standpoint because you’d think it would go to the same direction every time. I wonder, in some of these cases that come and go, if it is not necessarily a spinal cord lesion that is permanent, but rather some degenerative old age changes that create intermittent muscle spasms on one side. That would explain something that is more likely to be reversible and the signs could be more vari- able,” says Johnson.
“This is just conjecture, however. Unfor- tunately, a lot of these cases are old horses that often have other problems as well. Sometimes when they don’t recover, they end up being euthanized because that’s not the only thing that is wrong. Sometimes, even when we do postmor- tem exams, we can’t figure out what the actual cause was, or can’t be certain about it. Other times, we see multiple old-age changes in the vertebral column but not necessarily anything
in the spinal cord that explains the dramatically abnormal gait. That’s one of the reasons that
I’ve hypothesized that this might be happening on a functional or muscular level rather than a permanent spinal cord lesion,” she says.
“In my geographic region, for some reason we seem to hear about more cases in the winter, and I don’t know whether that’s because these are old horses with arthritic changes (and winter is harder on them because cold weather
aggravates arthritis pain) or whether these horses are slipping on ice and have bad footing. Mud and ice could be an issue. For whatever reason, I hear about more cases in the winter. Some of them come into the clinic here, and with some I just talk to the veterinarians on the phone when they call and ask my advice. It’s not that common, so with a lot of the veterinar- ians I talk to, it might be their first encounter with this syndrome,” she explains.
“When I talk with owners who have horses with this syndrome, I tell them the prognosis for making this horse 100% better and getting it back into ridden work is poor. There are not many horses that develop this problem and recover enough to go back to work. Some of them can be comfortable in retirement in a pas- ture, but it depends on the case,” says Johnson.
“If we want to try to figure out what the problem was, usually we look for EPM (ideally with a spinal tap, if that’s feasible) and/or treat for EPM if they have a positive blood test. With some of these horses, it’s challenging
to try to do a spinal tap because they are so unstable; it’s really hard to get that procedure done,” she explains.
“Ideally, we test for EPM, and potentially treat for EPM, and then consider doing a bone scan (nuclear scintigraphy) to look for pelvic fractures. We can also check for fractures with ultrasound. Radiographs can also detect some pathology in the pelvic region but a lot of times we cannot get really good views unless you put the horse under general anesthesia and that’s often the last thing you want to do with old horses with problems,” she says.
“We offer various types of imaging to look for some of these potential problems and we can also maybe do some ancillary diagnostics
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