Nerve roots exit your spinal cord and form nerves that travel into your arms or legs. These nerves allow you to move your arms, chest wall, and legs. These nerve roots may become inflamed and painful due to irritation, for example, from a damaged disc or a bony spur.
A selective nerve root block provides important information to your physician and is not a primary treatment. It serves to prove which nerve is causing your pain by placing temporary numbing medicine over the nerve root of concern. If your main pain improves after the injection then that nerve is most likely causing your pain. If your pain remains unchanged, that nerve probably is not the cause of pain.
By confirming or denying your exact source of pain, it provides information allowing for proper treatment, which may include additional nerve blocks and/or surgery at a specific level. Selective nerve root blocks are similar to epidurals, but instead of putting medication in to cover all of the nerve roots, selective blocks are done so as to cover just one or two nerve roots.
The membrane that covers the spinal cord and nerve roots in your spine is called the dura membrane. The space surrounding the dura is the epidural space. Nerves travel through the epidural space before they form the nerves that travel down your arms, along your ribs and into your legs. These nerve roots may become inflamed, for example, due to irritation from a damaged disc or contact with the bony structure of the spine. A selective epidural injection places anti-inflammatory medicine over the nerve root and into the epidural space to decrease inflammation of the nerve roots therefore reducing your pain. The epidural injection may assist the injury to heal by reducing inflammation. It may provide permanent relief or provide a period of pain relief for several months while the injury/cause of your pain is healing.
The selective nerve root block (SNRB) is a procedure that anesthetizes an individual nerve root, either within the neck (‘cervical’), or in the back (‘thoracic’ or ‘lumbar’), thought to be responsible for the patient’s pain. The nerve root sheath is injected and anesthetized with the intent of relieving this pain. This procedure is sometimes referred to as a ‘Foraminal Block.’ The SNRB procedure delivers a low volume of concentrated medication directly into the affected nerve root sleeve.
Back Pain is often multifactorial and difficult to diagnose because the symptoms overlap considerably with those of other degenerative disorders of the spine. The SNRB is useful in both the diagnosis and the treatment of back pain; therefore, it is both a diagnostic as well as a therapeutic procedure. In other words, if we inject a medication within the suspected nerve root sleeve and the pain improves, we are fairly confident that this nerve root is responsible for the pain; conversely, if we inject a medication and the pain is no better, this implies that this nerve root is likely not responsible for the pain.
Nerve Root Impingement
Patients with pain from nerve root irritation often have an anatomic cause, which is usually the result of a nearby structure pushing on, or impinging on the nerve, causing irritation of that nerve.
The most common causes of this are either a disc abnormality or an adjacent bone spur, either of which, when in close proximity to the nerve, can irritate it and cause pain in the distribution of that nerve.
If there is irritation of a nerve in the back or neck, it may cause symptoms of pain, and usually this pain is in the distribution of that particular nerve, referred to as radicular pain.
SNRB is most effectively used in patients with radicular pain.
These patients should have recent imaging studies (CT or MRI scan), which in many instances help to identify the cause of pain. Not all patients will have an identifiable cause for the pain on imaging, but all should have radicular symptoms. Electrodiagnostic studies such as EMG are useful in distinguishing peripheral neuropathy, entrapment and radiculopathy.
The procedure is explained to the patient, questions are answered and informed consent is obtained.
The patient is placed prone (stomach down) for lumbar or thoracic injections, or supine (face up) for cervical injection on the fluoroscopic table, and the area is sterilely cleansed with povidone-iodine (Betadine) and alcohol.
The exact level is located with the fluoroscope, and the skin overlying this area is anesthetized (numbed) with lidocaine. This is either to the right or left of midline on the back.
A needle is sterilely advanced along the nerve root sleeve, which typically elicits a mild degree of radicular pain in the distribution of that nerve. It is important for us to know whether the pain elicited is similar to the patient’s pain (concordant response), or dissimilar (discordant response).
Typically, as small amount of water-soluble contrast (dye) is injected to confirm proper needle tip position.
Once this is confirmed, a mixture of anesthetic (lidocaine or bupivacaine) and anti-inflammatory medication (steroid) is injected.
The needle is slowly withdrawn
This procedure may be performed with either CT or Fluoroscopic guidance.
What will happen after the procedure?
Immediately after the procedure, you will get up and walk around and try to imitate something that would normally bring about your usual pain. You will then report the percentage of pain relief and record the relief you experience during the next week. We ask that you remain at the Clinic until you feel you are ready to leave.
You may not be able to drive the day of your procedure. Your legs or arms may feel weak or numb for a few hours. You may be referred to a physical therapist immediately afterwards while the numbing medicine is still working. If the doctor prescribes physical therapy, it is very important that you continue with the physical therapy program.
Although you may feel much better immediately after the injection (due to the numbing medicine), there is a possibility your pain may return within a few hours. It may take a few days for the steroid medication to start working.
You may experience some weakness and/or numbness in your legs a few hours after the procedure. If so, do not engage in any activities that require lifting, balance and coordination.
Drink plenty of clear liquids after the procedure to help remove the dye from the kidneys.
General Pre/Post Instructions:
You should eat a light meal within a few hours before your procedure. If you are an insulin dependent diabetic, do not change your normal eating pattern prior to the procedure. Please take your routine medications (i.e. high blood pressure and diabetic medications). Do not take pain medications or anti-inflammatory medications the day of your procedure. You need to be hurting prior to this procedure. Please do not take any medications that may give you pain relief. These medications can be restarted after the procedure if they are needed. If you are on Coumadin, Heparin, Plavix or any other blood thinners (including Aspirin), or the diabetic medication Glucophage you must notify this office so the timing of these medications can be explained. You will either be at our clinic facility for approximately 1-3 hours for your procedure. You may need to bring a driver with you. You may return to your normal activities the day after the procedure, including returning to work.
Risks of nerve root injection?
Increased localized back pain, neck pain, arm pain or leg pain can be expected from several days to several weeks and rarely several months. There is a rare risk of permanent injury to nerve tissue with weakness or loss of sensation. There is also a rare risk of complication from anesthesia used to make you feel more comfortable during the procedure.
As with any procedure, there is a risk of significant complications. The most common side effects from the nerve root block can include (but are not limited to):
- Allergic reactions to medications
- Infection (occurs in less than 1 per 15,000 injections)
- Post-injection flare (nerve root irritation with pain several hours after treatment, which may last days or weeks)
- Depigmentation (a whitening of the skin)
- Local fat atrophy (thinning of the skin)
- Destruction of a motor or sensory nerve in the path of the needle
- Bleeding, nerve injury, organ injury and death are rare but possible