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Dorsal root ganglion block (DRGB) and possible pulsed radiofrequency lesioning

If you are considering having a Dorsal root ganglion block or have a procedure planned, it is important to know all you can about it. This includes:

why you need this procedure
what it will be like
how it will affect you
what risks are involved
any alternatives.

The information here is a guide to common medical practice. Each hospital and doctor will have slightly different ways of doing things, so you should follow their guidance where it is different from the information given here. Because all patients, conditions and treatments vary it cannot cover everything. Use this information when making your treatment choices with your doctors. You should mention any worries you have. Remember that you can ask for more information at any time.

What is the problem?

You have an inflamed nerve root in your back. This is usually caused by irritation from a bulging (prolapsed) intervertebral disc, commonly called a ‘slipped disc’. This causes pain running down from your back and into your arm or leg, depending on whether the damaged disc is in your neck or lower back. If the problem is in your neck it may be affecting your arm. If the problem is in your back it may be affecting your leg. Sometimes, a single nerve may be damaged without an intervertebral disc problem.

What is an intervertebral disc?

The vertebrae are the bones that make up the spine. The front of each vertebra is solid and is called the body. This is where the disc fits. There is an intervertebral disc between each vertebra. The intervertebral discs act like shock absorbers to let the spine bend and twist. They spread the impact when you jump up and down. Each disc can be considered as having two parts, rather like a soft centred sweet. The tough outer rim is bound to the vertebra above and below. The middle of the disc is soft and it is this part that prolapses meaning it bulges out of place.

The spinal cord only runs part way down the spine. It stops at the level of the lowest ribs. Below this spinal nerves run down the vertebral canal to the correct gaps between the arches. These nerves, packed in the canal, look like the tail of a horse and are called the cauda equina in Latin.

The spinal nerves and cord carry feeling impulses from the body up to the brain and impulses from the brain down to the muscles.

Behind the body of each vertebra is an arch of bone, called the lamina. The arches form a channel called the vertebral canal. The spinal cord runs down the vertebral canal from the brain, protected by the bony arches.

Spinal nerves run out from the spinal cord through gaps between the arches. These are the nerve roots. They run to different levels in the trunk, arms and legs. The lowest spinal nerves run to the buttocks and bladder.

What is a dorsal root ganglion block?

A dorsal root ganglion block is used to treat a number of different painful conditions. The injections are given into your back, placing the needle into the gap (foramen) in the spinal column where a particular nerve exits the spinal cord. The spinal nerves look a little like a Christmas tree. The spinal cord is the trunk and the nerves are branches leaving the trunk in pairs all the way down, one to the left and one to the right.

Needles can be inserted through the muscles of the back to lie alongside the nerves. Anti-inflammatory steroid drugs can then be injected onto the nerves. The pain coming from a single nerve, that has been irritated and inflamed, can be treated in this way. The pain is sometimes felt in the back but more commonly it is felt in the muscles and skin that the nerve supplies.

An inflamed intervertebral disc that is bulging towards the gap where the nerve leaves the spinal cord is the most common cause for irritated nerves. By targeting the painful area, a dorsal root ganglion injection bathes the nerves in local anaesthetic and steroid solution, relieving pain and inflammation. Pain from inflamed nerves felt in the leg, called sciatica, or in the arm, called brachalgia, can be treated.

If steroid is used only a small amount of steroid is needed. It will not cause any of the side effects sometimes associated with taking steroid tablets. They are not the same kind of steroids that athletes may take to build muscle.

More recently, the nerve root at the second lumbar level has been targeted. This nerve root has been identified as the ‘spaghetti junction’ of pain signals for the spine. A dorsal root ganglion block may be used at the second lumbar (L2) level. This can be used to reduce pain coming from worn or torn discs at any level in the spine. This would be tried after the pain from has failed to respond to normal treatments.

What has gone wrong?

You have suffered general wear and tear (degeneration) or damage from an injury to the intervertebral discs in the spine. When the disc is inflamed the nearby nerves become irritated. These nerves supply sensation to the limbs. When the nerves are irritated, the brain is fooled into believing that the limb is injured. This is not the case; the problem is in the spine. Sometimes the nerve itself is damaged without an intervertebral disc problem.

The aims

The aim of the procedure is to reduce the inflammation of the disc and therefore relieve the irritation of the nerve next to it. This reduces arm or leg pain and some of the spinal pain. Damaged nerves can also be treated directly with injections around the nerves themselves.

The benefits

Your pain should be reduced and you should be able to move around more easily. You can then exercise to prevent the problem happening again. If successful, this treatment can avoid the need for surgery.

Are there any alternatives?

By the time that you have the dorsal root ganglion block you should have already tried other more simple treatments. These include rest, painkilling and anti-inflammatory tablets, and physiotherapy with exercise.

What if you do nothing?

If you do nothing there are several things that may happen:

With time and rest the inflammation and pain may settle on its own
The pain and difficulty in moving around may remain the same
The pain may increase
The disc may become further damaged and injure the nerves that control movement. You may then develop weakness and difficulty moving your legs or arms. Some of this may be permanent
In severe cases you may lose control of your bladder and bowels as the nerve that controls them may be damaged

Who should have it done?

The following groups of patients should have the procedure done:

Patients with limb pain caused by inflamed discs
Patients with pain from damage to a single nerve
Patients with low back pain that has not settled by other means

Who should not have it done?

Each patient must make the final decision to proceed or not. If you are unhappy about the procedure for any reason you should not continue.

There are specific medical situations when a dorsal root ganglion block should not be done and they are as follows:

When a patient is on medication that prevents their blood from clotting, such as warfarin. This would lead to more bleeding than normal. It may be possible to stop the medication a few days before the procedure. This will need to be discussed with your doctor
When a patient is suffering from an illness that prevents blood from clotting, such as haemophilia. This would also lead to more bleeding than normal
When there is infection of the skin over the site where the needle needs to be put in
When a patient has a bloodstream infection

Author: Dr Sean White FRCA. Consultant in pain and anaesthesia.