Nerve Blocks: Medication Injections
Blocks are injections of medication onto or near nerves. The medications that are injected include local anesthetics, steroids, and opioids. In some cases of severe pain it is even necessary to destroy a nerve with injections of phenol, pure ethanol, or by using needles that freeze or heat the nerves. Injections into joints are also referred to as blocks. Although not technically correct, such shorthand is commonly used.
Purpose of Nerve Blocks
- Blocks with local anesthetic can be used to control acute pain. (Hence, the shot at the dentist or the epidural block for a surgery or a delivery.)
- Pain and injury often makes nerves more sensitive, so that they signal pain with less provocation. Think about lightly brushing against your skin when you have a sunburn. Blocks can provide periods of dramatic pain relief, which promotes the desensitization of sensory pathways.
- Steroids can help reduce nerve and joint inflammation and can reduce the abnormal triggering of signals from injured nerves.
- Blocks often provide diagnostic information, helping to determine the source of the pain.
Remember, blocks are not the best treatment for all pain problems. Often blocks are not possible, too dangerous, or simply are not the best treatment for the problem.
The most common spinal injection is the lumbar epidural steroid injection. This is particularly useful for pain that radiates from the lower back into a leg, and is caused by disc herniation or spinal stenosis (narrowing around the nerves) which triggers nerve root irritation.
- Similar injections can be very useful in the cervical spine, where the symptoms will extend into the arms.
- Thoracic epidural steroid injections are most commonly used to reduce the pain associated with herpes zoster (shingles). Such blocks may reduce the risk of developing persistent postherpetic neuralgia (ie, pain that persists long after the shingles' skin eruption has healed).
The facet joints of the spine can also cause pain. Injections into the facet joints or blocks of the nerves that go to the facets can often be very helpful with these pains. This problem is more common in the lumbar spine, but also occurs in the neck.
Discograms (intradiscal injections of contrast under fluoroscopy or CT imaging) can determine if and which disc is the source of the pain. The results of discography can help a surgeon identify which levels of the spine require surgery.
If the patient has a painful disc, they may be a candidate for intradiscal electrothermoplasty (IDET). In a procedure similar to a discogram, a wire is temporarily inserted into the disc and used to heat the disc. This destroys the invading sensory nerves and causes the proteins of the disc wall to reshape and slowly strengthen (over a period of 3 to 6 months). The procedure cannot be done if the disc has already severely degenerated.