Nerve block

Regional nerve blockade, or more commonly nerve block, is a general term used to refer to the injection of local anesthetic onto or near nerves for temporary control of pain. It can also be used as a diagnostic tool to identify specific nerves as pain generators. Permanent nerve block can be produced by destruction of nerve tissue.

Therapeutic Uses
Nerve blocks can help patients who suffer from lower back pain, neck pain, sciatica (from a herniated disc), spinal stenosis, reflex sympathetic dystrophy (a complex regional pain syndrome), shingles, cancer, and painful peripheral vascular disease. It can also be used in the treatment of migraine headaches. Proper patient selection is important.

Methods
Temporary nerve blocks are achieved by combining a local anesthetic (such as lidocaine) with epinephrine, a steroid (corticosteroid), and/or opioids. Epinephrine produces constriction of the blood vessels which delays the diffusion of the anesthetic. Steroids can help to reduce inflammation. Opioids are painkillers. Injection nerve blocks can be either single treatments, multiple injections over a period of time, or continuous infusions.

Permanent nerve block can be effected using include alcohol or phenol to selectively destroy nerve tissue, cryoanalgesia to freeze nerves, and Radiofrequency ablation to destroy nerve tissue using heat.

Nerve blocks are sterile procedures that are usually performed in an outpatient facility or hospital. The procedure can be performed with the help of ultrasound, fluoroscopy (a live X-ray) or CT. Use of any one of these imaging modalities enables the physician to view the placement of the needle. A probe positioning system can be used to hold the ultrasound transducer steady.

In addition, electrical stimulation can provide feedback on the proximity of the needle to the target nerve.

Complications
Nerve blocks, like other medical procedures, are not risk-free. There is a possibility of side effects and complications from the procedure, needle puncture, and medications used. The most critical factor in the efficacy of a nerve block is the proper location of the target nerve.

Complications include:


 * Infection
 * Allergy reactions
 * Increased pain

Nerve blocks in Veterinary medicine
Short-term nerve blocks are useful in regionalizing the source of pain during lameness examinations in horses. A local anesthetic alone is injected perineurally to desensitize tissues beyond the site of injection. For example, the palmar digital nerves can be blocked to investigate pain arising from the sole and heel area of the hoof. If pain is arising from this area, the horse will stop limping. If the source of lameness arises from higher up in the leg, the horse will continue to limp, and a nerve block can be performed higher up the leg. Because there are essentially no motor neurons in the lower limbs of horses, the risk of weakness or ataxia is negligible.