What are nerve root blocks?

The vertebral column is made up of vertebrae (see number 1 in Figure 1) in between which can be found the so-called intervertebral discs (number 2 in the Figure) that allow the vertebrae to move against one another. Each vertebra has two small paired joints (facet joints) with the vertebra above it (number 3 in the Figure) and two small joints with the vertebra below it (number 4 in the Figure). There is a nerve root that emerges from between two vertebrae (number 5 in the Figure). These nerve roots can be the cause of your pain, for example when they are damaged by a disc prolaps in the back. This nerve root is important for passing on pain signals.

Figure 1. Oblique view from the back of the lumbar vertebrae with part of the pelvis (see text).


To find out which nerve root is important for the area where you feel pain, we must first perform a test block of this nerve root. This is done by anaesthetising this nerve root (number 5 in the Figure) with an injection so that it can no longer pass on pain signals.

Since we do not know beforehand exactly which nerve root is the one causing your radiating pain, a test block usually involves anaesthetising three different nerve roots on one side. Three appointments are therefore made at the surgical day-care centre.

In a permanent nerve root block an electrical current is applied to the nerve root via a needle so that it heats up and becomes blocked and can therefore no longer pass on pain signals.

Test blocks and permanent blocks of a nerve root can be applied to the cervical, thoracic and lumbar vertebrae.

What should I be aware of before undergoinga nerve root block?

Any of the following situations should be reported to your pain specialist if he proposes nerve root blocks:

  • If you are pregnant: since X-ray equipment is used, pregnant women may not undergo nerve root blocks and a new appointment has to be made.
  • If you are ill or have a fever on the day of treatment you cannot undergo nerve root blocks, in which case a new appointment will have to be made.
  • If you are allergic to iodine, bandages, anaesthetics or contrast fluids, you should notify your pain specialist before the appointment for treatment is made.
  • If you are taking blood thinners, you should notify that your pain specialist before the appointment for treatment is made. He will then consider whether the use of certain medications should be ceased temporarily.

How should I prepare for a nerve root block?

  • No special preparations, such as an overnight bag, are necessary because the treatment is carried out on an outpatient basis.
  • You may eat before treatment and take your normal medication.
  • N.B.: this does not include blood thinners, as mentioned above.
  • Make sure you have someone to take you home, because you may not drive for 24 hours.

How does a nerve root block work?

  • The treatment will be performed in the surgical day-care centre, where you will be asked to change into a surgical gown. This gown closes at the back.
  • A nurse will escort you to the treatment room, where there is a treatment table, an X-ray machine and television monitors.
  • Depending on where the sleeve injection is to be performed, you will be positioned on the treatment table on your back or stomach.
  • With the help of the X-ray machine and a metal ruler, the exact location of the sleeve injection near the nerve root will be determined.
  • This place is marked on the skin with a felt pen.
  • The area around this site is then disinfected with a cold, red liquid.
  • The pain specialist covers the area with sterile drapes.
  • After a local anesthetic has been applied to the skin, the pain specialist, by means of fluoroscopy (via the television monitor), will insert the needles in the correct place.
  • Some contrast fluid is also injected to enable the position of the needle to be clearly visible.
  • In nerve root test blocks small amounts of anesthetic are injected around the nerve root to temporarily block the nerve root.
  • This numbness may last for several hours, and then return to the same pain level as before the nerve root test block.
  • You will then be asked to get dressed and return to the waiting room.
  • After half an hour, your pain specialist will inquire whether the nerve root test block clearly reduced your pain.
  • If this is not the case, you will have to make a new appointment with your own pain specialist to discuss further possible treatment options.
  • If the nerve root test block clearly reduced your pain, then an appointment will immediately be made at the day centre for a PRF treatment of the nerve root.
  • The procedure for a permanent nerve root block (PRF treatment) is exactly the same, but in addition to local anesthetics small electrical currents are administrated to the nerve root.
  • You will feel a tingling sensation.
  • When you feel this, you must tell the treating pain specialist straight away, and not wait for it to become painful.
  • The pain specialist will ask you where you feel the sensation and you don't have to point the place with your finger.
  • By means of a special device, the pain specialist can read the distance from the needle to the nerve root.
  • If the needle is in the right place the PRF treatment is performed.
  • Interrupted (pulsed) series of small electrical currents are used. These small currents modulate of the nerve root to decrease the pain.
  • You will then be asked to get dressed and make an appointment at the pain clinic after six weeks with your own pain specialist.
  • The effect of treatment will be checked and further policy will discuss with you.
  • On the day of the treatment you should slow down and is advised not to participate for 24 hours in traffic.

What are dangers and side effects of nerve root blocks?

After an nerve root block, the following complications or side effects can occur:

  • As possible side effect of nerve root blocks a temporary numbness of the skin at the side of the treatment can occur.
  • Touching of the skin in this area can be unpleasant and painful.
  • It will eventually disappear after a few weeks.
  • Sometimes an allergic reaction for the injected substances such as contrast fluid can occur.

When can I expect pain relief after the treatment?

  • After pains can occur following a nerve root block. This may last a week but will eventually disappear.
  • The optimum results of treatment are seen after six to eight weeks.
  • Around this time, a new appointment with your pain specialist will be made.
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