Selective Nerve Root Block (SNRB)/Perineural Injection


This fact sheet relates to selective nerve root block/injections, a type of pain relieving injection which is performed at Melbourne Radiology Clinic. This procedure is also known as a “foraminal block/injection”, “nerve root block/injection” and “periradicular block/injection”. The injection relieves pain by delivering anti-inflammatory medication to an inflamed nerve. A CT (Computed Tomography) scan will be used to guide the procedure.

Download PDF Patient Information Sheet Melbourne Radiology Clinic - Selective Nerve Root Injection Patient Information Sheet


A nerve root block is used for patients who suffer from pain from a “pinched nerve”, also known as radicular pain. This may involve the arms, neck, body and legs. Radicular pain usually involves the legs where it is commonly known as sciatica.



Risks of spinal procedures are rare and include:

The Procedure

You will be asked to wear a gown with the selected area of the spine exposed. Spinal injection procedures are completed with you lying face down in a CT scanner. We will ensure that you are as comfortable as possible.

A series of planning images are performed, with the area of needle entry planned on the computer terminal and then marked on your skin. The radiologist will then clean your skin with an antiseptic wash and inject local anaesthetic into the injection site. This results in a stinging sensation which is temporary until the skin becomes numb, usually taking 10-30 seconds.

A fine needle is then passed through the skin and tissues, constantly manipulated under CT guidance until it contacts the intended nerve. When gentle needle contact is made with the nerve you will experience a brief pain that many patients describe as an “electrical, nerve-like shooting” pain. This pain will usually be in the same area of the body and/or character as the pain that you have come in to have treated. Occasionally, it may be more intense at the time of needle contact. This is common, confirms the correct position of the needle and is normal part of the procedure. At this point, the cortisone and local anaesthetic are injected. Just as local anaesthetic stings when it injected into the skin, so to will a stinging sensation occur in the area that the injected nerve supplies sensation to. This lasts approximately 10 seconds.

Important information to tell your doctor prior to treatment

Serious side effects are rare, however if you have an existing condition, this must be discussed with your referring doctor before having treatment. People with local skin or systemic infections are at greater risk of having an infection spreading into the spine after spinal injection treatment. Therefore, if you have a skin infection, which may include wounds, boils or rashes, please tell your doctor or arrange to have the procedure performed at a later date.

Following the procedure

At most, you will feel some minor discomfort in the back. As local anaesthetic has been injected into the spine most patients will be pain free. Since local anaesthetic is also administered around a nerve, your arm or leg (depending on whether the nerves in the neck or lower back have been injected) may feel numb, heavy, clumsy, weak or even cold. This usually reverses in approximately 20-40 minutes. Most patients are observed in the clinic for at least 30 minutes and are discharged after this point only if walking safely and feeling well. You should not drive for the rest of the day. The following day you may return to work and gradually increase your activities.


Please discuss any medical illnesses with your doctor before booking the recommended procedure.

Follow up

The radiologist conducting the spinal injection will send your referring doctor a report.


Whilst every effort is made to keep your appointment time, the special needs of complex cases, elderly and frail patients can cause unexpected delays. Your consideration and patience in these circumstances is appreciated.