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Peripheral and diagnostic nerve blocks

A peripheral nerve block places local anaesthetic around a specific nerve to interrupt pain signals from the area it supplies. It is used to identify which nerve is responsible for a pain, and sometimes to treat it.

Some pain follows the territory of a single nerve. Pain along a surgical scar, pain after a fracture or crush injury, or pain in a defined patch of skin or muscle may all point to one identifiable nerve. Blocking that nerve tests the theory directly.

Diagnostic use. If local anaesthetic around a nerve substantially relieves your pain for the duration it is active, that nerve is likely carrying the pain. If it does not, the source is elsewhere — which is equally useful to know, and often spares people further treatment aimed at the wrong target.

Therapeutic use. Anti-inflammatory medication is usually included alongside the local anaesthetic, and this is what can give relief well beyond the anaesthetic's duration — commonly weeks to months, and sometimes longer. Longer-acting options including radiofrequency treatment may be considered.

Common targets. These include nerves of the chest wall and abdomen after surgery, nerves supplying the shoulder, hip and knee, occipital nerves at the back of the head, and nerves involved in pelvic pain. Region-specific pages cover several of these in more detail.

On the day. Most peripheral blocks are performed under ultrasound guidance, which shows the nerve and surrounding structures in real time. The skin is cleaned and numbed, a fine needle is advanced under direct vision, and a small volume of local anaesthetic, usually with anti-inflammatory medication, is injected. Most take 10–20 minutes. Sedation is generally not required.

Afterwards. Numbness in the nerve's territory is expected and resolves as the anaesthetic wears off. You will be asked to record pain levels over the following hours, since that record is the diagnostic result. Any longer-lasting benefit from the anti-inflammatory component develops over the following days. Protect a numb area from heat, cold and pressure until sensation returns.

Risks. Whilst pain procedures are generally safe and well tolerated, all procedures carry risks. The specific risks relevant to you and your procedure will be discussed with you, and written information provided, before you decide to proceed.