My legs are weird. There are all sorts of things going on in my body, so it's really hard to understand the effect these things have on my legs. They can do certain things, but not others, which is a bit of an enigma which stumps most medics. I wanted to share an analogy I've thought of that explains how I feel about what I feel.
First, though, I wanted to look a bit at why I and others with EDS have these problems - why is it that I have a bit of control over my legs, but not as much as I'd like? Why is it that I can feel pain from within, but not from without? Why can't I feel things that touch my legs, and why can't I feel where they are in space? I have to admit, I haven't found all the answers. I think it'll take a fair bit more research, not only from me but from the scientists out there!
Anyway, what I have got here is a general sense of why proprioception doesn't work well in EDS, and what effects this can have. Hopefully it's interesting to all, whether you're a bendy or not. It's got rather long so I'll leave the analogy for another time (which will also give me a chance to make it make more sense!). By all means come back for that another time, but if you're interested in a heavily potted version of the science then read on...
ProprioceptorsSomething I've known for a long while is that many of my problems stem from the fact that I have terrible proprioceptors. Proprioceptors are handy little things that can be found all over the body: in muscles, in tendons, ligaments, joints; even in the ear. They are mechanoceptors with the specific ability to detect movement in the body. The information that they detect is fed into nearby nerves and ultimately to the central nervous system, which is how your brain is able to control things it can't see - it can just feel the angle of your foot, for instance, thanks to the feedback from proprioceptors.
One of the types of proprioceptor is the muscle spindle, which is found in most of the skeletal muscles and is essentially a stretch receptor. The combined messages from muscle spindles help the brain to detect the length and velocity of a muscle - and therefore the position of a body part. Muscle spindles help us to know how far we need to stretch our arms to reach out for an object, or how far to move our legs when we walk.
|Muscle spindle diagram from here!|
Even in healthy people, with well-functioning muscle spindles, the system isn't nice and straight-forward, as if we were robots wired up. Many joints can move in different directions, many muscles cover more than one joint, and many spindle afferent nerves fire with what seems to be a rather well-meaning but ultimately detrimental enthusiasm, meaning that attempts by scientists to 'read' the nerve signals and translate them into biomechanics have limited success. The body does seem to do a better job of sorting this all out, but the generalisation of the response isn't always good news for humans.
Golgi tendon organ
Another type of proprioceptor is the Golgi tendon organ (GTO). They can be found in the areas where muscles and tendons join together, and they're really good at picking up muscle contraction. That's because the GTO is weaved with collagen fibrils which, when a muscle contracts, straighten to adapt. This activates the GTO afferent and therefore sends a signal to the brain that the muscle has contracted. The GTO also fires a bit when a muscle is stretched, but does so far less than the muscle spindle.
|GTO from here|
Proprioceptors and EDS
Doctors have found that many people with EDS have impaired proprioception because the feedback reaching the brain is insufficient, either in quality or quantity. They're not entirely sure why this should be the case, but the fact that collagen is a vital component of muscle spindles and GTOs, and is badly affected by EDS, is likely to play a big role. This means that people with EDS have a very poor concept of where precisely a joint or a part of a limb is in space if they can't see it - because they simply can't feel it. Poor proprioception could even explain why so many people with EDS suffer from dysautonomic conditions such as POTS - because stretch sensors in the cardiac muscle can also be faulty.
Some of the main causes of problems in EDS that are being researched in more detail include:
- weakened collagen in the nerves as well as within proprioceptors
- damage to peripheral nerves because of constant injuries
- an interesting little article talks a bit about how our senses weave themselves together. Further sensory problems exist for many with EDS (for example, problems with eyesight, hearing, pain sensation, taste/smell, vibration sensing, etc.) so there is less 'help' for our proprioceptors even though we have more need of the 'help'.
How does it affect people with EDS?The practical implications of these problems can be enormous. They include:
- muscle hypotonia
- poor postural control - which is not just 'sitting up straight' - for example, unless they're held in place by braces, my feet have a really bad tendency to twist and writhe without me knowing, so that to the onlooker it looks as if they've been cut off and stuck back on backwards! A bit of info on the extra thought that goes into it is here. More info generally, and regarding the impact of poor postural control on balance, can be read here.
- dyspraxia or general 'clumsiness'; being accident-prone (read more here and here)
- 'flailing' movements and poor spatial awareness
- inability to co-ordinate body movements without looking, e.g. in the dark or if the body part is out of sight (e.g. if I stick my leg out behind me, I have no idea how high it is. If I try to walk in the dark, even with things to hold onto, I fall over because I can't see what I'm doing). This leads to poor balance and lots of falls - have a look at this.
- gross and fine motor developmental delay/inaccuracy
- various researchers (such as these guys) have found various effects of connective tissue hyperdistensibility (i.e. being too stretchy/bulgy) upon muscle function
- tremors, spasm (/muscle cramp)
- autonomic disorders including POTS (info on this and more here)
- chronic pain (basically anything you find about EDS will mention this)
- movement disorders making movement ataxic or athetoid
A good general overview of a whole host of neurological problems in EDS can be found here, and is well worth a read if you've made it this far!
The mind gameThere are also psychological implications, such as:
- patients are frequently misunderstood, especially since many of the problems happen at a cellular level and do not necessarily show up in standard neurological testing or scanning.
- this poor understanding by friends, family and the medical profession, combined with constant pain and illness and isolation, unsurprisingly means that people with EDS often suffer from anxiety and depressive disorders.
- some patients develop 'kinesiophobia' (a reluctance or even refusal to move certain parts of the body, stemming from a learned fear of injury - read more here). I have to say that I don't really relate to this anymore - I try to move as much as I can because I know that it is the best way to keep myself moving. However, when I was younger and knew less, I was certainly guilty of it. I didn't move my back properly when I fractured it and as such it has been stuck ever since. Use it or lose it, people!