Selective Nerve Root Block (SNRB): A Day-Care Procedure to Diagnose and Treat Nerve Pain

In short: A selective nerve root block (SNRB) is an image-guided injection of local anaesthetic and steroid around a single spinal nerve root. It is a day-care procedure — done under local anaesthesia in about 15 to 30 minutes — used to diagnose the exact source of nerve pain, predict how well surgery would work, and relieve the pain itself. Key facts at a glance Type: Minimally invasive, image-guided injection (C-arm / live X-ray) Setting: Day care — home the same day, no general anaesthesia, no stitches Duration: About 15–30 minutes Three roles: Diagnostic, prognostic, and therapeutic Treats: Sciatica and nerve-root pain from a slipped disc or spinal narrowing What is a selective nerve root block? A selective nerve root block is a minimally invasive, image-guided injection. Using a C-arm (live X-ray) for precise guidance, the surgeon places a fine needle next to one specific spinal nerve root and injects a small amount of local anaesthetic, usually combined with a steroid. A tiny amount of contrast dye is used first to confirm the needle is at exactly the right nerve before any medication is given. Unlike a general epidural, an SNRB targets a single, named nerve — and that precision is what makes it so useful. The three roles of an SNRB 1. Diagnostic — pinpointing the pain generator Many patients have MRI scans showing changes at more than one level of the spine, and imaging alone cannot always tell which level is actually causing the pain. By numbing one specific nerve root, an SNRB tests it directly: if the pain disappears after that root is blocked, that root is confirmed as the source. This is especially valuable when the scan and the symptoms do not clearly match, or when several levels look abnormal. 2. Prognostic — predicting the result of surgery Because an SNRB confirms which nerve is responsible, it also helps predict how well surgery is likely to work. When a patient gets clear — though temporary — relief after blocking a particular nerve root, it strongly suggests that surgically decompressing that same root will relieve the pain. This makes the SNRB a valuable prognostic tool: it helps the surgeon and patient decide, with more confidence, whether surgery is worthwhile and exactly which level to treat. 3. Therapeutic — relieving the pain The steroid injected alongside the anaesthetic reduces inflammation around the irritated nerve. For many patients this provides meaningful relief lasting from weeks to months, sometimes allowing them to avoid or delay surgery while continuing physiotherapy and recovery. How the procedure is done (day care) You lie face down on the procedure table. The skin is cleaned and numbed with local anaesthetic. Under live X-ray (C-arm) guidance, a fine needle is guided to the target nerve root. A small amount of contrast dye confirms the exact position. The anaesthetic and steroid are injected, and the needle is removed. After a short observation period, you go home the same day. No general anaesthesia is needed and there are no stitches. Most patients are in and out within a few hours. What to expect afterwards Some patients notice relief within hours, as the local anaesthetic takes effect — this is also the part that gives the diagnostic answer. The steroid’s anti-inflammatory effect builds over the following days. It is normal to rest for the remainder of the day and briefly avoid strenuous activity. Your surgeon will explain how to record your pain relief over the next hours and days, because that information is exactly what guides the next step in your treatment. Is it safe? A selective nerve root block is generally very safe when performed by an experienced spine surgeon under image guidance. As with any injection, minor and usually temporary effects — such as short-lived soreness, a brief increase in pain, or temporary numbness — can occur, and more significant complications are rare. Your surgeon will review your suitability and any medications, such as blood thinners, beforehand. Who performs the procedure? Dr. Balaji Bashyam is a Consultant Endoscopic & Minimally Invasive Spine Surgeon in Chennai with 16 years of overall experience and 10 years dedicated to spine care. He trained at the CMC Vellore spine unit and completed advanced endoscopic fellowships in Germany. You can read more about his training and credentials here. He offers image-guided selective nerve root blocks as a day-care procedure and helps patients understand every option — non-surgical and surgical — before deciding. Get a precise diagnosis for your back or leg pain If sciatica or nerve pain has not settled, a selective nerve root block can identify the exact cause and often relieve it — as a simple day-care procedure. To book, call 9003185183 or request a consultation online →. Frequently asked questions Is a selective nerve root block a day-care procedure? Yes. A selective nerve root block is performed under local anaesthesia and usually takes about 15 to 30 minutes. After a short period of observation, the patient goes home the same day, with no general anaesthesia and no stitches. Is a nerve root block used for diagnosis or treatment? It is used for both. As a diagnostic test, blocking a specific nerve root confirms whether that root is the source of pain. As a treatment, the injected steroid reduces inflammation and can relieve pain for weeks to months. It also has a prognostic role, helping predict how well surgery would work. What is the difference between an epidural and a selective nerve root block? An epidural injection bathes a broader area of the spinal canal, while a selective nerve root block targets one specific, named nerve root. That precision lets an SNRB not only relieve pain but also pinpoint which nerve is responsible — something a general epidural cannot do as clearly. Does a nerve root block mean I will need surgery? No. Many patients get lasting relief from the block itself and avoid or delay surgery. When surgery is being considered, a good response to the block helps confirm which level to treat and predicts a better surgical outcome, but the block does not by itself mean surgery is required. How long does the relief from an SNRB last? The local anaesthetic gives relief within hours, which helps with diagnosis. The steroid’s effect develops over a few days and can last from several weeks to a few months, varying from person to person. Is a selective nerve root block painful? The skin is numbed with local anaesthetic first, so discomfort is usually minimal — most patients describe brief pressure rather than pain. Mild soreness at the site for a day or two is normal.