Nerve root blocks and lumbar sympathetic blocks

Your doctor has requested that you have a nerve root block either to help diagnose the cause of your pain or try to relieve it. 

We hope that the following information will answer some of the questions you may have about this procedure.

What is a nerve root?

Nerve roots exit the spinal cord and divide into nerves that travel to your arms and legs. These nerve roots can become inflamed due to pressure from nearby bone spurs or intervertebral discs. Inflammation of nerve roots may cause pain in the back, neck/arms and/or the legs. A nerve root block provides important information for your doctor and may also provide you with some relief from pain.

Why do I need to have a nerve root block done?

The procedure is designed to prove which nerve is causing your pain by placing temporary numbing medicine over the nerve root of concern. If your pain improves after the injection then that nerve is the most likely cause of your pain. If your pain remains unchanged, then that nerve is probably not the cause of your pain.

What is injected around the nerve root?

The injection is a combination of local anaesthetic (a numbing agent) and steroid (an anti-inflammatory agent). The local anaesthetic works immediately and the steroid begins to work within 2-3 days.

How do I prepare for a nerve root block?

There is no preparation for this procedure; you can continue to eat and drink as normal.

If you are diabetic please inform the doctor before the examination as there is a possibility that your sugar levels will vary after the injection. It is important that you continue to monitor your levels carefully for several days and consult your GP if necessary.

What will happen during the procedure?

You will be shown to a cubicle where you will be asked to undress in private and put on a gown. If you need assistance we can provide it.

You will then be shown into the X-ray room for the examination and introduced to the staff performing the procedure. You will be cared for by a small team including a radiologist/pain physician, radiographer and nurses.

Before the examination begins the radiologist/pain physician will explain what they are going to do and then ask you to sign a consent form.

You will then be asked to lie on your front or back on the X-ray couch. The skin will be cleaned and the doctor will inject a small amount of local anaesthetic under the skin. This stings for a few seconds and the area then goes numb.

The radiologist/pain physician will then direct a very small needle just next to the nerve root using the X-ray machine to guide the needle. Sometimes the needle can touch the nerve itself in which case you may feel a sharp pain going down your leg. This will only last for a second or two. A special dye called contrast medium is then injected around the nerve root. This shows up on the X-ray machine to confirm the needle is in the correct position. When the pain consultant/radiologist is satisfied with the needle position, the pain killing medicine will be injected along the nerve root.

How long will it take?

You will be awake throughout the procedure, which lasts about 15 – 30 minutes.

Will it hurt?

You may feel a little pressure or discomfort, which may travel down the arm/leg, during the injection of the pain killing medicine. This will last for only a few seconds.

Afterwards your leg may feel numb or weak for up to 24 hours. You will be asked to wait for 30 to 60 minutes before going home and you should not drive for the rest of the day. You will need to arrange for someone to take you home. Some people find that their pain feels worse for 2-3 days after the procedure. This is because the steroid can sometimes irritate the nerve. Do not worry if this happens, as it will settle down by itself. 

If your leg becomes numb you may need to stay in hospital overnight.

Are there any risks associated with a nerve root block?

Generally it is a very safe procedure. Potential complications are uncommon and include:

  • Bleeding or haematoma (a bruise under the skin) – this should settle down by itself.
  • Infection – contact your GP if you experience any redness or tenderness at the injection site.
  • An allergic reaction to the contrast dye – please inform the doctor doing the nerve root block if you have any allergies.

Please inform your pain consultant if you take any blood thinning medication such as Warfarin, Clopidogrel, Rivaroxaban, Dipyridamole, Dabigatran. It is very important you contact us PRIOR to attending your procedure. Please note this list is not exhaustive.

Please also inform the pain consultant if you are a diabetic as there is a possibility the steroid may affect your blood sugar levels. It is therefore important you monitor your levels carefully for several days after the procedure and consult your GP if necessary.

The procedure uses X-rays to confirm that the needle is in the correct place. The amount of X-rays used is very small however female patients who are or who may be pregnant should inform the department before attending for 
their appointment.


We hope this information is helpful. If you have any questions either before, during or after the procedure the staff at the Pain Clinic or X ray department will be happy to answer them.

The telephone number of the X-ray department can be found on your appointment letter.

Additional Information for Pain Clinic patients having a lumbar sympathetic block.

What is Lumbar Sympathetic Block?

There are nerves running either side of the lumbar spine, that control blood supply to the muscles and  skin of the legs. Injecting these nerves with local anaesthetic and/or a drug, may help your pain and improve your mobility.

What will happen during the procedure?

The procedure is done in the same way as a Nerve Root Block, except a dye is not injected.

What will happen after the procedure?

You will be asked to stay for approximately 30-60 minutes in the recovery area/Medirooms.

Your blood pressure, pulse and temperature will be monitored and you may need to lie down for a little while.

You should not drive after this procedure. You will need an escort to take you home and stay with you overnight. 

If your leg becomes numb, you may have to stay in hospital overnight.

You can restart your normal activities the following day.


Botwin et al (2002) Fluoroscopically guided lumbar transforaminal epidural steroid injections in degenerative lumbar stenosis: an outcome study. American Journal of Physical Medicine and Rehabilitation 81(12) 898-905

Vad et al (2002) Transforaminal epidural steroid injections in lumbosacral radiculopathy: A prospective randomised study. Spine 27(1) 11-15

Waldman S (2004) Atlas of Interventional Pain. 2nd Edition. Saunders. Philadelphia

NHS Constitution. Information on your rights and responsibilities. Available at

How to contact us:

Pain Clinic
Gloucester House
Southmead Hospital
BS10 5NB

0117 4147361

If you or the individual you are caring for need support reading this leaflet please ask a member of staff for advice.

© North Bristol NHS Trust.  This edition published February 2020. Review due February 2022. NBT002599

Nerve root blocks and lumbar sympathetic blocks