Nerve Blocks

Nerve blocks may involve local anesthesia, regional anesthesia or analgesia, or surgery; dentists routinely use them for traditional dental procedures. Nerve blocks can also be used to prevent or even diagnose pain.

In the case of a local nerve block, any one of a number of local anesthetics may be used; the names of these compounds, such as lidocaine or novocaine, usually have an aine ending. Regional blocks affect a larger area of the body. Nerve blocks may also take the form of what is commonly called an epidural, in which a drug is administered into the space between the spine's protective covering (the dura) and the spinal column. This procedure is most well known for its use during childbirth. Morphine and methadone are opioid narcotics (such drugs end in ine or one) that are sometimes used for regional analgesia and are administered as an injection.

Neurolytic blocks employ injection of chemical agents such as alcohol, phenol, or glycerol to block pain messages and are most often used to treat cancer pain or to block pain in the cranial nerves. In some cases, a drug called guanethidine is administered intravenously in order to accomplish the block.

Surgical blocks are performed on cranial, peripheral, or sympathetic nerves. They are most often done to relieve the pain of cancer and extreme facial pain, such as that experienced with trigeminal neuralgia. There are several different types of surgical nerve blocks and they are not without problems and complications. Nerve blocks can cause muscle paralysis and, in many cases, result in at least partial numbness. For that reason, the procedure should be reserved for a select group of patients and should only be performed by skilled surgeons. Types of surgical nerve blocks include:

• Neurectomy (including peripheral neurectomy) in which a damaged peripheral nerve is destroyed.
• Spinal dorsal rhizotomy in which the surgeon cuts the root or rootlets of one or more of the nerves radiating from the spine. Other rhizotomy procedures include cranial rhizotomy and trigeminal rhizotomy, performed as a treatment for extreme facial pain or for the pain of cancer.
• Sympathectomy, also called sympathetic blockade, in which a drug or an agent such as guanethidine is used to eliminate pain in a specific area (a limb, for example). The procedure is also done for cardiac pain, vascular disease pain, the pain of reflex sympathetic dystrophy syndrome, and other conditions. The term takes its name from the sympathetic nervous system and may involve, for example, cutting a nerve that controls contraction of one or more arteries.