The causes of migraines are mysterious. Researchers believe that migraines may be due to a complex process that involves nerves, chemicals in the brain, and dilation of blood vessels in the head. The good news is that a new treatment called an occipital nerve block may help manage some migraines so that sufferers can live a normal life. The sensation of pain in the head is conveyed by many different nerves. The greater occipital nerves are especially important. They travel from the upper spine, through muscle and into your scalp; and they are responsible for transmitting pain signals over much of the back and top of the head. In some cases, their influence reaches as far as the forehead. Numbing or blocking this pain pathway with injectable medication, called an occipital nerve block (ONB), may relieve debilitating headache pain in some people with migraines. The procedure involves injecting a local anesthetic, such as lidocaine, bupivacaine or both, under the skin and into deeper tissue in the back of the head in the region of the nerves. If inflammation contributes to your pain, an anesthetic plus steroid combination may be used. The effect of local anesthetics wears off in hours, but the migraine relief from steroids can last longer, even weeks or months in some cases. Physicians who perform occipital nerve blocks at Johns Hopkins consider the best candidates for the procedure to be patients whose pain occurs mostly on one side at the back of the head. Occipital nerve blocks can also be effective for some people whose scalps are tender, which may be an indication of inflamed occipital nerves. Complications of the procedure are generally rare. Because this procedure is so new, controlled clinical trials are needed to prove the effectiveness of blocking nerves with both local anesthetics and the combination of anesthetics and steroids. The procedure for performing an occipital nerve block has not been standardized, so it is difficult to compare published results. In fact, many insurance companies will not cover the cost of injecting local anesthetics and/or steroids to block nerves for the treatment of migraine and other sources of head pain due to the lack of convincing clinical data that the procedure works.