The lateral branches of the dorsal rami of the spinal nerves

What on earth are they and do you need to care about them? (Hint: you probably should).

If you’d asked me two years ago to tell you about the lateral branches of the dorsal rami of the spinal nerves or LBDRSN (to use a particularly awkward acronym), I would have struggled, other than to say they were branches of your spinal nerves.

Indeed, they’re inordinately under-researched (until now) and often completely ignored in both anatomy studies (dissections, ew!) and clinical studies (actually trialling treatments, medications etc). Because they are mainly found in the outside layers (skin, fat, fascia – the “gristle” of the body that keeps you together), they are usually removed by anatomists, who are more interested in the stuff underneath (muscles, joints), and therefore completely ignored. In looking for a decent drawing of these little guys, the most recent one I could find was 100 years old (from Gray’s Anatomy, 1918).

Why? Well, the majority of our research into back pain has centred around large, easy to find structures, like discs, joints, and muscles.

However, the few researchers who’ve taken a close look at these structures have turned up some interesting findings. These nerves branch off the spinal cord, weave their way around and sometimes though – this is IMPORTANT – the muscles close to the spine, and then pierce their way through the fascia (connective tissue that is often under tension as we move or fight gravity) to make their way to your skin, where they tell you things like whether it is hot, cold or your shirt is made of itchy material.

The problem is that these little nerves can be subject to some pretty extreme forces at the points where they pass through muscles, or through the fascia (especially if that fascia is especially gristly – see picture below), [attach pic 3] and this can make them a little bit “grumpy”. This grumpiness is sent to the body’s computer in the brain, where anything can happen – muscle tension, postural changes, different tissues become more sensitive – in a bid to protect yourself.

How do we know all this? Well, in recent years clinical studies (including one at the University of Notre Dame, which I was involved with) have finally started to turn their attention to poor old LBDRSN and have discovered some interesting stuff, like that by injecting local anaesthetic into these nerves at the point where they are potentially being affected, scientists and doctors were able to “turn off” patients’ pain, which helps to prove that these nerves are playing a role in that person’s pain. And in some cases, these were patients that had been diagnosed with something else (eg a disc or joint problem), and had unsuccessful outcomes with other treatments.

For me this was a revelation – it meant that there was nothing technically “wrong” with the patients where this is happening (except the body’s “warning system” going off, which is probably a good thing), and it meant that those clients I would see with “tightness”, muscle tension but no real sign of injury suddenly started making sense.

If there isn’t anything terribly wrong with them (apart from sensitive skin and fascia), often the fear and worry associated with back pain goes away, and people are happy to get moving sooner and more.

 

Pics refs:

  1. https://web.duke.edu/anatomy/mbs/Lab02_MBS/Lab2.html
  2. https://etc.usf.edu/clipart/52600/52687/52687_cutaneous.htm
  3. https://stemcelldoc.wordpress.com/2011/12/30/low-back-pain-cluneal-nerve-entrapment/

All retrieved 6/5/19

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