FWD: RSD World News-Advanced Pain Management Techniques

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From: byrd45 (Original Message) Sent: 7/15/2005 7:27 AM

Philip Kim, MD

Neurostimulation is the application of precise targeted electrical
stimulation on nociceptive pathways. Electric stimulation has a long
history in medicine for treating various ailments. Beyond the
application of electrodes on the skin such as in transcutaneous
electrical nerve stimulation (TENS), electrodes have been applied
directly to nociceptive pathways.

The nociceptive pathways are made up of tracts in the central and
peripheral nervous systems. The central nervous system includes
nociceptive pathways in the spinal cord and brain, specifically the
dorsal roots, dorsal ganglion, spinothalamic tracts, and all ascending
neural tracts to the cerebrum. The peripheral nervous system includes
pathways outside the spinal cord, specifically various plexuses and
peripheral nerves.
Components of the System

Spinal cord stimulation involves the placement of an electrical system
to block nociception. The system comprises the surgical placement of
epidural electrodes, cables, and radiofrequency transmitter or
battery. Much of this method has evolved from cardiac pacemaker
technology. The minimal invasiveness and trialing has led to the
success of this approach. Neurostimulation can be placed during an
outpatient procedure, with local anesthesia and sedation. The patient
experiences minimal discomfort when the system is placed and during
the postoperative period.

Before the system is placed, a simple trial of percutaneous lead
placement can be performed. In this case, the patient goes home with
the lead connected to a screener box. No incision is necessary and the
procedure is performed using only local anesthesia. The purpose of the
trial is to determine the effectiveness of the stimulation for
relieving pain and improving the patient's quality of life. If this
temporary method allows the patient to sleep better, use less pain
medication, and sit and stand longer, then it becomes more convincing
to place an internalized spinal cord stimulation system.
Mechanism of Action

The mechanism of action of spinal cord stimulation is based on the
placement of epidural electrodes along the dorsal columns. Originally,
spinal cord stimulation was called dorsal column stimulation. It is
thought that spinal cord stimulation works through the gate-control
theory of Wall and Melzack, which theorizes that stimulating large
nerve fibers (A beta fibers) can inhibit or modulate smaller nerve
fibers (A delta or C fibers), transmitting nociceptive input possibly
at the dorsal root or horn of the spinal cord. Strategically placed
epidural electrodes stimulate the dorsal columns (A beta fibers) to
inhibit or modulate incoming nociceptive input through the A delta or
C fibers. Ongoing research suggests that spinal cord stimulation may
inhibit transmission in the spinothalamic tract, activation of central
inhibitory mechanisms influencing sympathetic efferent neurons, and
release of various inhibitory neurotransmitters.
Pain Conditions

Spinal cord stimulation can be applied to treat neuropathic pain
conditions, including arachnoiditis, complex regional pain syndrome
(formerly called reflex sympathetic dystrophy), neuropathies, brachial
and lumbosacral plexopathies, radiculopathies, deafferentation
syndromes, phantom limb pain, and postherpetic neuralgia. Clinical
studies and 30 years of clinical experience have continued to show
efficacy in these conditions. Visceral syndromes such as interstitial
cystitis, chronic abdominal pain, and chronic pancreatitis have been
treated with limited success.

Intractable pain caused by peripheral vascular disease and angina can
be treated with spinal cord stimulation. Indeed, in Europe, the
primary indication for spinal cord stimulation once was peripheral
vascular disease. The success of stimulating the lower extremities may
be based on microvascular blood flow changes via alterations in
sympathetic outflow. It could also be that one is treating a
concurrent ischemic neuropathy in the lower extremities.

Limited success of spinal cord stimulation may depend on the extent of
peripheral vascular disease. Based on one study,[1] spinal cord
stimulation does not reduce the incidence of amputation in the lower
extremities. The same rationale for using spinal cord stimulation for
treating peripheral vascular disease is now being applied in clinical
trials of patients with intractable angina, including those with
patent coronary vessels who continue to have intractable angina and
patients who are not candidates for coronary bypass and stent
procedures. It is theorized that these patients have a neuropathic
condition and microvascular blood flow deficiency.

Some painful conditions cannot be stimulated along the spinal cord and
therefore are not responsive to spinal cord stimulation. Thus,
peripheral nerve and plexus stimulation has evolved as a complementary
neurostimulation approach. The mechanism of peripheral nerve and
plexus stimulation is unclear since the electrodes are not stimulating
the dorsal columns. Some postulate that a variation of the
gate-control theory is involved at the peripheral nervous system
level. Moreover, peripheral nerve stimulation may activate central
structures leading to inhibition of various nociceptive pathways,
similar to the way acupuncture results in somatosensory cortex activation.
Clinical Trials

Current clinical trials and experience have involved 3 different
patient groups. First, intractable headaches caused by neuropathies of
the trigeminal and occipital nerves may benefit from neurostimulation.
Trigeminal neuralgia is a painful constant condition for which
neurodestructive neurolysis may not work. Neurostimulation of the
actual trigeminal ganglia has been performed. Stimulation of various
branches of the trigeminal ganglia, such as supraorbital and
auriculotemporal nerve, has been performed with limited success.
Ongoing clinical research is under way on occipital nerve stimulation;
electrodes are placed percutaneously and surgically along these nerves
at the subcutaneous occiput level. The peripheral nerve stimulation
system is placed in a manner similar to the spinal cord stimulation
system.

Second, stimulation of the sacral nerves or lumbosacral plexuses can
be beneficial for painful conditions resulting from chronic abdominal,
pelvic, genital, and anal pain syndromes. Specific conditions that
have been treated include interstitial cystitis, coccydynia,
pyelonephritis, pancreatitis, rectal fugax, and vulvodynia. These
perplexing syndromes are difficult to treat in significant part
because we lack a complete understanding of what perpetuates them.
Procedures allowing access to sacral and lumbosacral nerves include a
retrograde epidural approach and a sacral transforaminal approach.

Third, some peripheral neuropathies, neuromas, and plexopathies are
difficult to stimulate along the spinal cord and may not respond to
spinal cord stimulation. Surgically or percutaneously placed
electrodes along nociceptive pathways have been performed with
success. The most common sites are along the ulnar, median, common
peroneal, and saphenous nerves.
Conclusion

Neurostimulation of the central and peripheral nervous systems is
playing a vital role in the treatment of various intractable pain
conditions, including conditions for which we have limited
pathophysiologic understanding, such as complex regional pain
syndrome. Until we develop treatments that truly eliminate pain,
neurostimulation can play a major role in improving the quality of
life for pain patients. These systems do not damage neural pathways
and could be removed when curative therapy becomes available.

As patients and their physicians become aware of the benefits of these
techniques for managing intractable and difficult-to-treat pain
syndromes, more people may be interested in undergoing this kind of
treatment and will achieve improvements in the quality of their lives.
The comedian Jerry Lewis lives with intractable low back pain and has
attributed his spinal cord stimulation system with giving him his life
back. Hopefully, he will continue to talk about his life and persuade
others that they don't have "to live with it [pain]."

References

1. Horsch S, Schulte S, Hess S. Spinal cord stimulation in the
treatment of peripheral vascular disease: results of a single-center
study of 258 patients. Angiology. 2004;55:111-118.

Suggested Reading

Albutaihi IA, Hautvast RW, DeJongste MJ, et al. Cardiac nociception in
rats: neuronal pathways and the influence of dermal neurostimulation
on conveyance to the central nervous system. J Mol Neurosci.
2003;20:43-52.

Augustinsson LE. Spinal cord stimulation in peripheral vascular
disease and angina pectoris. J Neurosurg Sci. 2003;47(1 suppl 1):37-40.

Buschmann D, Oppel F. Peripheral nerve stimulation for pain relief in
CRPS II and phantom-limb pain. Schmerz. 1999;13:113-120.

Cameron T. Safety and efficacy of spinal cord stimulation for the
treatment of chronic pain: a 20-year literature review. J Neurosurg.
2004;100(3 suppl):254-267.

Erdek MA, Staats PS. Spinal cord stimulation for angina pectoris and
peripheral vascular disease. Anesthesiol Clin North Am. 2003;21:797-804.

Jessurun GA, Hautvast RW, Tio RA, DeJongste MJ. Electrical
neuromodulation improves myocardial perfusion and ameliorates
refractory angina pectoris in patients with syndrome X: fad or future?
Eur J Pain. 2003;7:507-512.

Murray S, Collins PD, James MA. Neurostimulation treatment for angina
pectoris. Heart. 2000;83:217-220.

Rushton DN. Electrical stimulation in the treatment of pain. Disabil
Rehabil. 2002;24:407-415.

Weiner RL. Peripheral nerve neurostimulation. Neurosurg Clin North Am.
2003;14:401-408.

Zamotrinsky AV, Kondratiev B, de Jong JW. Vagal neurostimulation in
patients with coronary artery disease. Auton Neurosci. 2001;88:109-116.
Philip Kim, MD, Medical Director, Center for Pain Medicine, P.C., St.
Francis Pain Center, Wilmington, Delaware
Disclosure: Philip Kim, MD, has disclosed that he has served as a
consultant for Medtronic.