A nerve root block is an injection of a mixture of local anaesthetic and hydrocortisone (steroid) around a nerve as it exits the spine. This is used when a particular nerve in the lower back is inflamed due to irritation from either a disc prolapse or narrowing of the spinal canal due to degenerative wear and tear. A nerve root block is not a cure but aims to alleviate your symptoms by reducing the inflammation caused by the mechanical irritation of the nerve. In patients who have had a MRI scan that shows problems at multiple levels a nerve root block can provide useful diagnostic information to help identify the source of your pain. It can also be called a foraminal or transforaminal injection

How do we do it?

A nerve root block is carried out as a day case procedure in an operating theatre. To minimize discomfort the injection is performed under sedation, which is administered by an anaesthetist. The needle is placed under x-ray guidance, and its position confirmed by injecting a small amount of dye that shows up on the x-ray image.

What Are the Risks?

Infection

There is a risk of infection at the injection site, but this is rare due to the use of sterile techniques. If you were to develop an infection then this does have the potential to make you unwell. You may require prolonged antibiotics and potentially surgery to treat the infection.

Bleeding

There is a very small risk of infection at the injection site, but this is rare. If you had some bleeding around the nerves following an injection there is a a very small chance that you may require an urgent operation to deal with this. To minimise bleeding we do ask that any medication that might increase your bleeding risk be stopped prior to the injection.

If you are on any medication that has the potential to thin your blood such as aspirin, clopidogrel, warfarin or any other blood thinning medication then we do need to know about this prior to the date of your injection.

Temporary "Floppy Leg"

Following a nerve root block your leg can go completely ‘floppy’ for a few hours. Once this has worn off you will be able to go home, and there should be no lasting effects. If this happens to you, it is important that you tell us when you come back for your follow-up appointment. We will also want to know if your leg pain disappeared whilst your leg was ‘floppy’.

Numbness

Following the injection you may have some numbness going down your leg and potentially also between your legs. This should settle over a day or so.

Pain Flare

Following the injection you may have some increased pain going down your leg. This will normally settle over a few hours.

Headache

Following the injection you may have a headache for a few hours. This should settle by the following day. There is a 1 in 1000 of the lining around your nerves being punctured when you have this type of procedure. This can result in a small leak of spinal fluid which is likely to cause a more problematic headache. If you have a persisting severe headache the day following your injection, then can you please contact the hospital to let me know so that we can manage this correctly. In this eventuality you may require a few days of bed rest or potentially a further injection into your back to put a patch over the area of leak.

Injection Site Discomfort

Following the injection you may have some localized soreness at the injection site, for which you can take some simple painkillers and it should settle over a few days.

Side Effects From The Injected Steroid

There are very few side effects when steroids are administered this way. Occasionally patients may notice some facial flushing, nausea, or mild abdominal cramps for a few days following the injection. There can also be a temporary disturbance to the menstrual cycle. Diabetics may find that the steroid alters their blood sugar control for a few days, so should monitor it closely.

Allergic Reaction

An allergic reaction to injected steroid and local anaesthetic is incredibly rare. However, you must inform us of any know allergies beforehand.

What Can I Expect Following the Injection?

You will normally be able to leave hospital once you are mobile and. This is normally 2-3 hours following your injection. There will be a small dressing over the injection site that can be removed after 12 hours.

As you will have had sedation you will be unable to drive for 24 hours following the injection, and will need to arrange for someone to collect you from hospital. We would advise that you have a restful day the day after your injection, but can return to normal activities the following day. There are no other restrictions following the injection.

For the first few weeks following your injection it is important that you keep a pain diary, documenting any relief that you have had. Please can you bring this information with you when you return to the clinic. Even a temporary reduction in pain is useful diagnostic information.

If further rehabilitation is recommended, it is important that you undertake this whilst you are pain free so that you gain maximal long-term benefit. It is important that you build up any unaccustomed activity gradually.

What Next?

You will be seen back in the clinic a few weeks after your injection. Your on-going treatment will be guided by your response to the injection.