Nerve Blocks: Diagnostic vs. Therapeutic

Before receiving radiofrequency lesions, patients selected on the basis of their history, examination, radiological and other studies, must undergo diagnostic injections (or blocks) to determine if the suspected pain generating structures – nerves themselves, the joints connecting the vertebra in the spine, and the sacroiliac joints for example – are indeed culprits in causing their pain. In these procedures, the nerves carrying pain information from the suspected generators are blocked or injected with local anesthetics. These drugs block the ability of nerves to conduct nerve impulses. For these blocks to be as accurate as possible, a small amount of local anesthetic (Novocaine) is applied only to the appropriate nerves and the results of those blocks evaluated within minutes. If the blocks eliminate all or the majority of your pain, you may then benefit from a radiofrequency lesion, in which the nerves from the pain generator are “blocked” by total or partial destruction, for several years. Some nerve structures may be destroyed without ill effects and others must be only partially damaged to achieve pain relief without side effects.

In general, unlike many pain management physicians, I perform relatively few therapeutic nerve blocks such as epidural steroid injections, blocks of spinal nerves, and blocks of the nerves supplying the facets (the joints connecting the vertebra) for two reasons. First, most of these blocks have little demonstrated long-term effect in most patients in whom they are used frequently. Second, many patients I see in consultation have already failed these therapeutic blocks. To the extent a block performed for diagnostic purposes provides relief, I wait for symptoms to return before resorting to more definitive interventional pain management strategies. Therapeutic blocks that I do perform include occasional nerve blocks of certain nerves in the head or face, nerves in other parts of the body, epidural steroid injections and blocks of nerves within the spine (spinals roots). The epidurals are performed for usually temporary relief of acute, or sub acute, pain due to either disc herniation or annular tears (tears in the pain sensitive covering of degenerated discs), both likely to heal eventually over two-to-three months.  However, they are capable of causing significant pain at times, despite oral steroids, until they heal. I may also use epidurals and root blocks to give several months of relief to patients with lumbar or low back stenosis, an arthritic narrowing of the spine. Stenosis, once severe, is ultimately a surgical problem.  However, there are those who cannot withstand stenosis surgery for medical reasons or for whom the surgery would result in severe chronic pain – albeit  distinct from that of stenosis – such as in cases requiring an extensive lumbar fusion as part of the stenosis operation. For these patients, pain management with medication and judicious use of injection therapy may keep them going with a reasonable functional existence and pain control. (Click here for more information on Stenosis.)

Sympathetic blocks for Complex Regional Pain Syndrome (CRPS) (formerly known as RSD or Reflex Sympathetic Dystrophy), while vastly over performed, may be of definite short and even long term therapeutic benefit in certain patients (see “Specialties” for a discussion of CRPS).  I perform these blocks in occasional, carefully selected patients with CPRS, defined by internationally accepted criteria, who have not had adequate relief from oral medication of various kinds, including narcotics, with a realistic expectation of a beneficial outcome but not a cure.  Some patients with CRPS who feel better when the limb is warm—not cold—may benefit from these blocks, and later, on a longer term basis, possible radiofrequency lesioning of the sympathetic nerve supply to an affected area.

On rare occasions, I also perform certain destructive nerve blocks, using alcohol or phenol, usually for the temporary control of certain facial pains and treatment of abdominal and pelvic cancer related pain.



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Emile M. Hiesiger, M.D.

The Corinthian
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New York, NY 10016
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