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Dorsal Root Ganglion (or Paravertebral or nerve root) Block

What is a Dorsal Root Ganglion Block?

The spine is made up of a column of 26 bones (vertebrae) sitting one on top of the other. At the top is the skull and at the bottom the pelvis. Between each vertebra and the next are pairs of small gaps called foramina, through which at each level a nerve root emerges from the spinal canal.  These nerves have small swellings on them at about the point where they come out through the foramina which are called the dorsal root ganglia and which contain the cell bodies of the nerve cells (axons).  Injection of local anaesthetic with or without a small dose of locally acting steroid to the foramen can be used to try to alleviate pain arising as a result of compression or irritation of the nerve in this area or other spinal pain.  This procedure is called "dorsal root ganglion block", or sometimes alternatively "paravertebral block" , "transforaminal epidural" or "nerve root block".

Where is the injection carried out?

You will be asked to attend the Day Surgery Unit for half a day (morning or afternoon) On the day you will be greeted by a nurse who will look after you until you go home. You may be asked to change into a gown and will be taken to one of the operating theatres for the procedure. 

How is the injection done?

You will be asked to lie on your front (for injections in the lower back, or on your back for injections in the neck) on a special table that allows us to use an X Ray machine to guide the injections.  The dose of XRays used is tiny: the machine intensifies a very small X Ray dose in a similar way to army night vision goggles.  X-ray pictures are taken throughout to ensure the needle is in the correct area. 

The skin overlying the joints is sterilised and a small amount of local anaesthetic is injected with a tiny needle to numb the skin.  Following this a fine needle is placed into the foramen, and a small dose of X Ray dye ("contrast") may then be injected to outline the nerve and confirm correct placement.  Once correct position is confirmed a small amount of local anaesthetic and sometimes steroid is injected into the foramen around the nerve.  

The steroid acts only around the area it is injected into and does not have the same effects as taking long-term steroids.

Does it hurt?

You do not need a general anaesthetic for this procedure.  Sometimes, on entering the foramen, there can be some temporary discomfort: the doctor will ensure pain is kept to a minimum by using local anaesthetic.   If there is any discomfort it is important to tell the doctor since this could indicate that the needle tip is coming very close to the nerve and we would obviously wish to avoid any risk of touching or harming it.  Once the procedure is over you may have some tenderness over the injection site but no worse than after any other type of injection.

How long will it all take?

Although the procedure itself usually only takes 10-15 minutes you will be asked to stay for up to an hour or so after the injection in the Day Surgery Unit before going home.

At home:

You may move around freely at home unless you have been advised to the contrary by a member of staff. Indeed, the patients who do best after this procedure are normally those who make use of the pain relief from the procedure to increase the amount of activity and exercise they do. You do not need to do any specific back exercises unless you have been instructed to do so.

Possible complications:

  • You may have mild discomfort at the site of the injection; this should last no longer than 48 hours. In a number of patients it can make your symptoms worse for about a week.
  • Occasionally you may get a numb leg which lasts for a few hours.  There is a very small chance of a temporary drop in your blood pressure.
  • As for any procedure, we have to warn you that there are very small chances of rare complications such as infection or damage to the nerve.  Potentially (though incredibly rarely) the needle tip could contact the bag of fluid that surrounds the spinal cord and nerve roots and cause a temporary leak of this fluid, with a resultant headache.  
  • If you have diabetes your blood sugar level can temporarily become less well controlled.
  • Very rarely people can be allergic to the injection, which results in redness and itching. This is not serious, but we need to know for future treatments.  Very occasionally you may feel some flushing sensations for the first day or two after the injection, as a normal side effect of the steroid.
  • Serious complications with this procedure are extremely rare, but if problems arise please consult the Pain Clinic Office, or your own doctor who will contact the Pain Clinic if necessary.

(Please see general comments on the Procedures page)


The Trust's information sheet on Paravertebral Block can be downloaded here

The Trust's information sheet on Dorsal Root Ganglion Block can be downloaded here



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Pain Service Website, Gloucestershire Hospitals NHS Foundation Trust
Webmaster Dr J G de Courcy, Consultant in Pain Medicine and Anaesthesia
email: pain.webmaster[at]

Page updated 22/6/2016