Medial branch blocks are an important procedure for treating back pain, and they’re quite frequently misunderstood. This misunderstanding is not only by people who have pain, but also by quite a number of practitioners and people who pay your insurance.
What people often don’t understand is what medial branch blocks are and why we should do them.
They are really valuable. If they’re done properly, they can lead a particular group of people with chronic spinal pain becoming virtually pain free.
The thing to understand about medial branch blocks is that they’re a diagnostic procedure. They’re not a treatment at all. Their real purpose is to clarify the cause of your back pain.
Medial branch blocks answer the question: is your pain coming from a particular facet joint in your back?
That’s all they’re designed to do. They’re not a treatment for back pain, and are not intended to give long term pain relief. But they do lead on to things which can give long term relief.
The facet joints occur in the spine at each level of the spine between C2 and C3, and C3 and C4 etc, all the way down your spine to lumber (L5) and sacral (S1.)
From your top of your neck, right down to the right down to your tailbone, in between each level of the spine, there are two facet joints. These joints are part of the mechanism that allows movement and support in your spine.
These joints can become damaged and this can cause chronic back pain in some people. However, they’re not the only structures that can do this.
Interestingly, if you look at the whole population of people with back pain, the commonest cause chronic lower back pain arises from the discs.
However, as you grow older, the facet joints slowly become more worn, and the incidents of pain arising from the facet joints starts to go up.
At some point, where people are in their fifties, facet, joints become more common than spinal discs as a cause of chronic back pain.
The important thing is that there is no easy way to sort out whether your pain is coming from the facet joint or from some other structure.
If you do a x-rays, a CT scan, an MRI scan, or even a fancier PET or SPECT scan, all of these scans will give you different bits of information. But none of them tells you whether your pain actually comes from the facet joint or from another structure.
This is what medial branch blocks do.
Each facet joint has two parts to it: a segment which comes from the top vertebra and a segment that comes from the bottom vertebrae. These segments are the two facets, which rub together and help support your back and allow movement at each segment. There are two facet joints at each at each level of the spine – one on each side.
There’s also a little nerve that comes from the top facet and supplies feeling and sensation from the top facet. That’s the first medial branch. The second medial branch comes from the lower facet. These two nerves run together, join into the spinal cord and send messages up to your brain.
Therefore, the only reason that your brain knows the facet joint exists is because of information from the two little medial nerve branches that supply that joint.
Normally the information stream from these two nerves is so small that you’re not even aware of these joints. However, if the joint becomes damaged, the nerves will start to send messages of pain.
As you get into certain positions, a damaged facet joint will send a message of pain up to your brain. You’ll not only feel the pain where the facet joint is, but in a certain distribution – larger area of your back. It can feel like an ache, a tearing pain, or a lancing pain.
If it gets particularly bad, then you can feel pain often, or even all the time. There may not only be one, but a number of facet joints causing you pain.
The issue is this: your back pain may be coming from the disc or the ligaments or the muscles or the tendons or the facet joint. It’s very hard to tell from a physical examination or even a scan which structure is truly causing your pain.
The way to answer the question: “is this pain from the facet joint?” is to put a tiny little needle onto the medial branch of that facet joint. You have to put local anaesthetic on the two medial nerve branches, and both parts of the facet joint.
The injection of local anaesthetic right on the nerve turns it off.
As soon as you do this, all information from the facet joint will stop being sent up to the brain. This works in the same way as if you have a terrible toothache, and then dentist puts in local anaesthetic: everything goes numb and the pain goes away.
If you numb the facet joint, then all the pain that was coming from the joint will be taken away. The doctor puts local anaesthetic on the tiny little medial branch nerves. He or she only injects 0.3 of a mil of anaesthetic, which is a tiny little amount.
This the test: if blocking facet joint nerve takes your pain away, then your pain is coming only from that facet joint.
It’s very specific test, and only works on the small proportion of people whose pain is only coming from their facet joints.
Now, if the pain is truly coming from your facet joints, then when the doctor does the block, the pain shouldn’t be just a little bit better.
It should be gone completely. After a successful the medial branch block, you should be able to move around, bend forward, shift around and do things that you can’t normally do.
This effect should continue only while the local anaesthetic is working. After a while, the anaesthetic will wear off, the feeling comes back into the facet joint, and the pain returns.
Because you’re doing the nerve block as a diagnosis tool, you need to be doubly sure this test is correct. You need to negate a problem that occurs with all interventions. The problem is called the placebo effect.
The placebo effect works like this: when you’ve lived with a pain for such a long time, and you’re about to get the nerve block, you think: “Oh my God, somebody is going to do something about this.”
The doctor does the block, and because you are so relieved, the power of your mind switches off the pain from your facet joints for a short period of time.
This placebo effect means that well over 30% of the time, the medial branch block will give relief to people even if it’s not the main cause of their pain.
To make the facet joint pain test more accurate, doctors have devised a further measure. Instead of just one nerve block, you do two nerve blocks, with a few days in between.
For one block, the doctor uses a short acting local anaesthetic. For the second block, the doctor uses a long acting local anaesthetic.
The person who’s having the nerve blocks has no idea which procedure uses long acting anaesthetic, and which one uses short acting. However the doctor does know.
What should happen is you get significant pain relief after each shot. By significant, the pain should go from 6 or 7out of 10, down to less than 1 out of 10. It should be an 80-90% reduction, not a 50% reduction.
There will be some discomfort because the doctor has stuck some needles in your back, but that should be greatly outweighed by the relief of having the facet joint pain switched off.
If the test is positive, the pain goes away for a short time with the short acting anaesthetic, and a longer time with the long acting one.
If that’s the case, you have two positive concordant medial branch blocks. This meansyou can be very confident that your back pain is coming from the facet joint.
Why is it so important to have a definite positive test? Because the medial branch block is a diagnostic test and the next step is treatment.
The long term treatment for facet joint pain is called a radiofrequency neurotomy. Neuro is nerve, otomy is cutting or destroying or damaging.
If you have two positive and concordant medial branch blocks of the tiny little nerves in your back, then the doctor can go on and do the radiofrequency neurotonomy of those nerves.
The doctor puts a probe into your back, parallel to these tiny little nerves in your back. The nerves are just 10 or 15 millimeters long, and as thin as your hair. This probe is positioned under an image intensifier, so the doctor can be sure their probe is accurately placed.
He or she then very carefully runs puts the probe parallel to the nerve, and turns on a microwave. That’s the radiofrequency. The tip of the probe will slowly heat up one degree at a time until it reaches 80 to 85 degrees centigrade. At that temperature, it will cook the nerve. It’s a tiny burn deep in your back, and just the little medial branch nerve will get zapped.
If your test nerve blocks have been done correctly and accurately, then you will the same pain relief from zapping the nerve as you did from the local anaesthetic injection.
In other words, if you had 7 out of 10 pain and it went down to 1 out of 10 with both nerve blocks, then after the radio frequency, you should get the same pain relief, but it’s going to be long term.
The pain relief now will last until the nerve grows back, which is an average of ten months to two years. For some lucky people, the pain never comes back.
The process is:
This procedure will then give you many months of pain relief. If your pain comes back, you can simply burn the nerves again.
It’s a very useful procedure, and the media branch blocks give you an enormous advantage. With them, you get to test first to see if the structure you’re targeting is the cause of the person’s pain.
This is unlike spinal surgery, where the surgeon looks at the MRI scan and says, “Oh, that’s the worst looking disc, I think will operate at that level.”
The surgeon has no way of actually knowing beforehand that the pain is definitely coming from that disc. It’s more of a best guess, because there’s no way of checking their hypothesis.
With successful medial branch blocks, you can be more than 90% confident that doing the radio frequency neurotomy will give the person the same pain relief as the blocks, long term. This is with caveat that the branch blocks have to be done accurately, under an image intensifier.
You can repeat the radiofrequency neurotomy as needed, because the intervention itself is actually minor. There’s no general anaesthetic involved, and most people take maybe four or five days for full recovery.
It’s an accurate and specific treatment for a very common cause of chronic spinal pain, either in your neck or your lumbar spine.
This procedure does require quite a lot of skill from the people doing the procedure, however it’s a repeatable and successful treatment.
If the medial branch tests don’t take away your pain, what do you do next?
It’s important to recognize that the facet joint is only one of many causes of spinal pain. Other structures which cause back pain are the discs, the tendons, and the ligaments.
When the pain is caused by something other than the facet joints, then the medial branches blocks won’t give pain relief, and doing a radiofrequency in your autonomy is a waste of your time.
If you have pain from another source, then you need to treat that structure. It’s also important to know that when you’ve had pain for a long time, you will have sensitization of your pain system in that area.
Treating pain sensitisation is another process, and you can find out more about it below.