Understanding Your Injection Results

This page explains, in general terms, how the result of a diagnostic spinal injection is worked out. Unlike a scan that produces a picture, a diagnostic injection produces information from how your pain behaves afterwards. Understanding what a "positive" or "negative" result means, and why the details matter, helps make sense of what your specialist is looking for — though only they can interpret your own result.

The core question is simple: did numbing a specific structure change your pain, and by how much and for how long? A meaningful, temporary reduction in your usual pain — during the time the local anaesthetic is expected to work — suggests the injected structure is contributing to your symptoms (a "positive" result). Little or no change suggests it is not (a "negative" result). This is why you are often asked to keep a pain diary and to note your activity: the timing and size of the change are the actual result of the test, more than any single number.

After the injection you may notice a period of numbness and relief while the anaesthetic works, sometimes followed by a temporary return or even brief worsening of pain as it wears off; if a steroid was included, any longer-lasting benefit tends to build over some days. Recording honestly what you feel, and when, gives your specialist the information they need. Occasionally a test is repeated or a different structure is tested next, depending on the response.

A diagnostic injection is only as useful as the interpretation of its result. Read carefully alongside your scans, symptoms and examination, it can confirm or rule out a suspected pain source and guide the next step — whether that is a targeted treatment, further tests, or a different approach. A "positive" result is not an automatic instruction to operate, and a "negative" one does not mean your pain is not real; both are pieces of a larger picture that your specialist puts together with you.

• —NICE — Low Back Pain and Sciatica in Over 16s (NG59)
• —Faculty of Pain Medicine, Royal College of Anaesthetists — Standards
• —British Association of Spine Surgeons (BASS)

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.