Is Thumb Arthritis caused by bad nerves? We’ve seen for years an association between thumb arthritis and subtle findings of carpal tunnel syndrome. What I mean by this, is that many patients who we evaluate for stem cell treatments of their CMC thumb joints also have issues we can detect in their median nerve (the one in the wrist that goes to the thumb and is involved in carpal tunnel syndrome). Are these two be linked? Does this mean that we need to be treating both problems as if they were one?
Last month a group of researchers looked at older thumb arthritis patients by checking for a common feature of nerve pain – widespread hypersensitivity. What does that mean? When nerves go bad, they first start to get hyper-sensitive. You intuitively know this from having a bad tooth, as it can first be quite sensitive to hot or cold or touch, long before it stops complaining because the nerve died off. This happens as a “warning signal” delivered by the body that there’s a problem with a nerve. Since the nerves are the internal wiring that direct every muscle as well as taking information from countless sensors to the brain, losing one due to damage, injury, or disease isn’t taken lightly by the body.
Getting back to our researchers, they took 16 patients with symptomatic thumb arthritis (CMC or base of the thumb) and 16 healthy controls. They then used a common system to measure pain hyper-sensitivity which was made up of a pressure device that measures the amount of pushing that the patient feels as pain. When nerves are bad, they interpret less pushing pressure as painful. They were able to show that patients with symptomatic thumb arthritis had lower pressure-pain thresholds not only over the thumb, but also the neck, the leg, and in other areas compared to controls. The first research study by this same group on the topic had initially only found the pain pressure sensitivity over the thumb, so why are they now finding it everywhere?
You may recall a seminal paper published a few years back entitled, “Arthritis doesn’t cause Pain, Pain causes Arthritis”. Meaning that the reason we keep failing to find great MRI and x-ray correlations between patients who have pain and patients who have arthritis is that arthritis is a nerve problem manifesting as a structural one. After decades of brain washing by the medical community that an MRI will surely show the cause of their pain, I have found that patients really have a hard time grasping this concept. So let me put it a different way. Your arthritis is bad because of bad nerves or bad nerves make your arthritis worse. So in this case, something causes the initial problem in the thumb joint. The joint nerves then become sensitized (read much more sensitive) which is a process that includes the spinal cord and all the nerves leading from the joint (i.e. the median nerve in the wrist). If it’s an acute problem that can heal (let’s say the person hit their thumb in a car crash), then this sensitization merely performs the role of telling the body that it needs to be careful with that thumb so that it heals (by making it and much of the surrounding hand hurt a lot). However, if it never heals, the sensitization can remain. In addition, it can also go the other way–pressure on nerves in the neck, shoulder, or wrist can trick the body into thinking the thumb is injured. Over time, this nerve problem elsewhere leads to bad muscle firing and bad chemicals being dumped into the thumb joint and this facilitates arthritis.
The upshot? More research is continuing to get the SANS approach described in our practice’s e-book, that nerves play a key role in the propagation of arthritis, so just looking at the joint in many cases is folly. So in this specific situation, in a patient with thumb arthritis, a 2-3 minute quick exam of the thumb and hand isn’t adequate. Instead, a detailed examination of the thumb, hand, wrist nerves, shoulder nerves, and neck spinal nerves should make up the routine investigation into the cause and possible treatments for thumb arthritis.