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Nerve Root Block

Nerve Root Block

Pain Management by a Nerve Root Block

A selective nerve root block or dorsal root ganglion block, is primarily used to relieve ‘Sciatica’. It is a targeted injection and done under some form fluoroscopy usually under sedation.

Occasionally, an imaging study (e.g. MRI) may not clearly show which nerve is causing the pain and occasionally am NRB injection is performed to assist in isolating the source of pain

The injection is done both with a steroid (an anti-inflammatory medication) and lignocaine (a numbing agent). Flouroscopy (live x-ray) is used to ensure the medication is delivered to the correct location. If the patient’s pain goes away after the injection, it can be inferred that the pain generator is the specific nerve root that has just been injected. Following the injection, the steroid also helps reduce inflammation around the nerve root. Pain relief due to this may occur between 3 days and 7 days after the injection

Success rates vary depending on the primary diagnosis and whether or not the injections are being used primarily for diagnosis. While there is no definitive research to dictate the frequency of NRB’s, it is generally considered reasonable to limit NRB’s to three times per year.

Technically, NRB injections are more difficult to perform than epidural steroid injections and should be performed by experienced doctors. Since the injection is outside the spine, there is a very small risk of a wet tap (cerebrospinal fluid leak). However, since the injection is right next to the nerve root, sometimes a NRB will temporarily worsen the patient’s leg pain (steroid flare).

Patient Journey for a Nerve Root Block

The procedure is performed as a day case procedure requiring a hospital stay of about 3-4 hours. Patients are asked to starve for 6 hours prior to the procedure to avoid problems during sedation. Clear liquids are permitted up to 2 hours before but no milky tea or coffee. Chewing gum is not permitted.

After a preliminary check on the ward to ensure blood pressure, pulse etc are within a normal range, I take a written consent from the patient and answer any further questions on the procedure. You would have to change into a gown and suitable theatre clothes.

The procedure is performed in theatre or in the X ray department under fluoroscopy.

An anaesthetist is in attendance as this procedure is performed under sedation. A venflon (intravenous cannula) is put in by the anaesthetist. While you lie on your tummy under the image intensifier, the back is prepared with a sterile solution after sedation is administered by the anaesthetist. This usually consists of a small amount of fentanyl(an opiate) together with midazolam. Although you are awake during this procedure, some patients may fell very drowsy or may not remember the event. It is generally perceived as a not unpleasant procedure.

Under X ray guidance a very fine needle is inserted close to the most inflamed area. This may reproduce the sciatica like pain and sometimes the anaesthetist tops up the pain medication aat this point. Presence of the needle within the nerve root sheath is confirmed by injection of a small amount of iodine consisting contrast (Omnipaque 240) to ensure that the outline of the nerve root is well seen and that the correct area is injected. The steroid and small amount of local anaesthetic is then injected. A small dressing or a sealant spray is used to cover the point at which the needle entered.

Upon return to the ward, a cup of tea or a snack is offered. You can get up and walk shortly after but driving is not permitted for 24 hours due to the sedation. Pain is often better for some time due to the local anaesthetic, but this can wear off leaving patients in more pain for some times upto 3.days.

What happens after the procedure?

Immediately after the procedure, the patient will be taken back to the recovery room or the ward. Patients are then asked to keep a pain diary and report the percentage of pain relief and record the relief experienced during the next week.They are asked to ring the office on telephone number 02083677007 to report any change.

The leg may feel weak or numb for a few hours following the procedure. This is fairly common and happens following a selective nerve root block. The following day or two may be more painful than before the procedure


These are rare. Some patients report an increase in pain for the first 2-3 days. This is quite normal and usually passes off. Strong pain killers may be required for some days after this injection.

The commoner problem is that the injection may not help the pain (20%).

This may be due to three reasons

  1. The injection may not be in the exact spot- this is rare as it is done under x ray control. Technically though the injection is difficult to perform especially if there are anatomical variations which are very individual. A repeat injection is sometimes required.
  2. The problem may be too much for an injection to resolve and Surgery may be required (eg. very large disc prolapse)
  3. Pain returns after an intial response- a repeat injection may resolve the problem

Rarer complications are infection, a flushed face lasting for 24 hours (due to preservatives in the medication) and very rarely some menstrual cycle disturbances in some women which usually settles after 2-3 cycles.

Infection is a very rare risk of this type of injection as is a CSF leak.


Pain relief of sciatica can be quite dramatic. The benefit could last long term. This can star between a few hours to a few days after the injection.

The success of a relatively minor injection may obviate the need for surgery

Who should not have a nerve root block?

If you are pregnant, there is a risk of radiation and therefore the procedure is not advisable.

If you are on medication like clopidogrel or warfarin- please let us know as injections could be dangerous in these situations.

If you have any concerns please discuss them with Mr. Bajekal or telephone the office 0208 367 7007

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