Neuropathic pain – what is it and why it matters
Not all pain is created equal. Neuropathic pain can have dire consequences on the horse’s well-being and is potentially the main culprit of explosive behaviour.
Neuropathic pain is generated in a different way than “normal” pain.
When dealing with problems in training, keeping and managing horses, pain is something we come across very often. When we have a horse that starts biting when being tacked up, a horse that starts refusing jumps, or picking up the wrong canter lead, a horse that spooks, a horse that is lazy, my money will always be on him being in pain. Most of the time, unwanted behaviour, dangerous behaviour and poor performance are due to pain. So, in if you have been around horses for a while, chances are you have witnessed a horse in pain. This is why it makes sense to know as much about it as possible, so we can learn to recognise it as early as possible and treat it as soon as possible.
In recent years, there has been more talk about neuropathic pain in horses. And I think this is really, really important. Let me tell you why. Let's look at a very brief description of the way pain is normally generated. When specialized nerve endings (nociceptors) perceive a stimulus as potentially threatening, they send a signal up to the central nervous system where the brain translates it into pain and then decides to do something about it (maybe move the hand away from the fire, or move the foot off the Lego block). This is normal pain. Neuropathic pain, on the other hand, is created in a different way. It comes about when the nerve itself is irritated or compressed. Because the pathway is different, neuropathic pain has very different characteristics. In humans, this pain is described as a shooting, stabbing or burning sensation. It can come about in episodes and it can be triggered by a stimulus that in itself shouldn't be painful. An irritated nerve being touched lightly, might feel like a mild electroshock.
Explosive behaviour can be triggered by neuropathic pain.
In horses, this kind of pain is often connected to explosive behaviours that seemingly come out of nowhere. A horse violently shaking his head, vehemently bucking his rider off after a jump or becoming actively aggressive towards his handler, might be suffering from neuropathic pain. Irritated, compressed or entrapped nerves can (in theory) happen anywhere, but the most common areas in horses seem to be the trigeminal nerve on the head (think nosebands), the nerves of the brachial plexus at the base of the neck (think dysfunctional thoracic sling) and the sciatic nerve of the hind end (think excessive lumbar stiffness). Another way in which neuropathic pain is different to normal pain is that it does not respond to NSAIDs. Because the pathway in which is generated is different, making it go away is much harder. There is much that we still need to learn about neuropathic pain in horses, but I believe it's important that we know it exists. Knowing neuropathic pain exists can help us when dealing with a horse who exhibits signs of explosive behaviour. It's also yet another reason to take extremely good care of the horse's musculoskeletal system. Well-fitting tack, a functional thoracic sling and a healthy hind end are the best measure we can take to decrease the risk of our horse having to deal with something as terrible as neuropathic pain.