Neurostimulatory and Neuroablative Procedures

CHAPTER 42 NEUROSTIMULATORY AND NEUROABLATIVE PROCEDURES



Jason E. Silvers, BS, James N. Campbell, MD, Charles E. Argoff, MD




1. What is spinal cord stimulation?


Spinal cord stimulation (SCS) provides electrical stimulation over the dorsal columns of the spinal cord through the placement of epidural electrodes. Although the mechanism by which SCS relieves pain remains unclear, SCS results in significant pain relief for an appropriately selected group of patients.



2. List the criteria for choosing patients who may benefit from spinal cord stimulation for treatment of pain




image The patient should have a clear diagnosis for which the procedure is indicated.


image Standard therapies to treat pain have been exhausted or are unacceptable to the patient.


image When feasible, temporary relief of the patient’s pain symptoms should be demonstrated by a trial of stimulation.


image The pain should be distributed such that spinal stimulation can stimulate the sensory fibers that serve the painful area and create paresthesias. It is difficult to stimulate the sensory fibers that serve the spinal column, and thus spinal axis pain usually does not respond to SCS. In spinal cord injury, the sensory fibers that would ordinarily serve the painful area may be severed. The underlying substrate for stimulation (the dorsal columns) is thus missing. Not surprisingly, SCS does not relieve pain in such patients.


image The patient must have a clear understanding of what to expect from treatment.



3. Give examples of conditions that may respond and of those that usually do not respond to spinal cord stimulation


The following conditions may respond to spinal cord stimulation:



image Radicular pain from failed back surgery


image Ischemic pain from peripheral vascular disease


image Pain from peripheral nerve injury


image Phantom limb pain or stump pain


image Complex regional pain syndrome (reflex sympathetic dystrophy, causalgia)


image Angina pectoris


The following conditions usually do not respond to spinal cord stimulation:



image Postherpetic neuralgia


image Pain from spinal cord injury


image Axial pain in failed back syndrome



4. What are the theoretical bases for stimulation-produced analgesia?


Although there is no clear unifying theory for stimulation-produced analgesia (SPA), the most frequently employed is the “gate control theory.” In its simplest form, this theory holds that stimulation of nonnociceptive fibers can inhibit the perception of activity in nociceptive fibers, and that there are central, descending pathways that also modulate the perception of pain. Electrical stimulation of certain central areas (most commonly the periventricular gray matter and thalamic nuclei) may produce analgesia through endogenous opioid mechanisms (see Chapter 1, Definitions).



5. Why is spinal cord stimulation for failed back surgery syndrome more applicable to radicular neuropathic pain than to axial low back pain?


It is easier to generate paresthesias in radicular distributions than in the midline of the lower back. Radicular paresthesias are elicited at almost all electrode positions, whereas achieving stimulation overlap of the lower back is technically difficult and may require complex electrode placement and extensive psychophysical testing.



6. What are some of the complications of spinal cord stimulation for treatment of chronic pain?


The most common complication of spinal cord stimulation for treatment of chronic pain is failure to achieve long-term pain control. Some of this may be the result of faulty patient selection. Occasionally, electrodes break or migrate from their initial site and analgesia wanes.


Other complications include infection at the site of the stimulus generator or a seroma collection.



7. What are implantable pumps for intrathecal drug delivery?


Implantable pumps consist of reservoirs, placed subcutaneously, which connect via a catheter into the intrathecal space. Implantable pumps allow physicians to administer opiate analgesics directly into the cerebrospinal fluid (CSF). The pumps are programmable so that the treating physicians can adjust dosages and delivery rates. The reservoir will have to be refilled on an intermittent basis: this is achieved by a percutaneous injection into the reservoir. Because the reservoir pump is driven by electricity, intermittent replacement is needed as the battery expires. More information on this technique is given in Chapter 41, Intraspinal Opioids.



8. What are the dose advantages of spinal epidural and subarachnoid opiate delivery versus systemic administration?

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Jun 14, 2016 | Posted by in PAIN MEDICINE | Comments Off on Neurostimulatory and Neuroablative Procedures

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