by Chester Pruett, MD
Intervening at the spinal cord level for pain management
is divided into three general categories. One category is
effecting pain relief at the spinal cord level by the use of
electrical stimulation. A second category is using medications
at the spinal cord level for pain relief. The third spinal
cord intervention would involve a surgical manipulation of
the spinal cord itself to obtain pain relief.
Electrical stimulation of the spinal cord, also known as
dorsal column stimulation (DCS), was first done effectively
in the 1970s by placing wire electrodes into the epidural
space and attaching them to a pulsed generator. The
equipment used was crude and would usually be effective
for a few days to weeks before failing. In 1983, commercial
sources became available for the equipment that
made it much more durable and reliable. DCS for controlling
chronic low back pain and/or leg pain was a nondestructive,
reversible procedure that has become an
attractive alternative for patients who may be facing or
have already experienced neuroablative procedures or
habituating opioid medications.
The exact mechanism of action of DCS is unknown.
Electrical stimulation of the spinal cord interferes with the
conduction of pain impulses through certain sensory pathways
and provides pain relief without changing any underlying
pathology.
The procedure is usually done in two stages. The trial
stage is done by placing one or more electrodes into the
epidural space, usually by a percutaneous approach. The
electrodes are attached to an external generator and pain
relief recorded for one to five days. If successful, a permanently
implanted generator and electrodes are done at a
later date.
Ohnmeiss, et al. (1996) concluded that spinal cord stimulation
can result in improved physical function and
reduced pain in selected patients with intractable leg pain.
Bell et al. (1997) reported that spinal cord stimulation is
cost-effective in treating patients with chronic failed back
syndrome. Most insurance companies approve DCS for
failed back syndrome, reflex sympathetic dystrophy and
ischemic limb pain secondary to peripheral vascular disease.
DCS is still considered experimental or investigational for
a variety of conditions to include occipital neuralgia, intercostals
neuralgia, phantom limb pain and post-herpetic
neuralgia. It has been used to treat the
failed neck syndrome, cervicogenic
headache and intractable angina, but
continues to await FDA approval for
these conditions.
The second category of intervention
places medications directly into the
spinal fluid. This is most commonly
done by placing a catheter into the
spinal fluid and attaching it to an
implanted pump. The most common
medication used is morphine sulfate,
hence the term “Morphine Pump.” Because most opiate receptors are located
in the spinal cord and brain, this is
a very efficient method for delivering
opioid medications. About one one
hundredth the intramuscular dose in
the spinal fluid is equipotent for most
opioids. Other medications such as
clonidine, baclofen, and ziconitide
have also been very effective in the
spinal fluid at relieving certain types
of pain.
Morphine pumps generally are
approved for cancer or malignant pain.
They are used less often for benign pain
due to a specific complication caused
by long term catheter implantation in
the spinal fluid. Over a long enough
time frame, the catheter can form a
granuloma in the spinal fluid which
can cause a paralysis below the level of
the catheter.
Surgical interventions of the spinal
cord include a cordotomy and sensory
rhizotomy. These procedures are
done very effectively by neurosurgeons
in certain selected patients.
In conclusion, DCS and spinal opiates
have provided newer, less invasive
options for the treatment of certain
pain conditions. They have been
proven to be cost-effective and in certain
patients, a most reasonable
approach to pain management.
Chester Pruett, MD is a graduate of LSU
School of Medicine in New Orleans. He
completed residency training at Brooke
Army Medical Center. After seven years
of active duty in the Army, he established
an office in the Oak Hills area. For the
last 25 years he has lived and worked in
the Methodist Hospital and Oak Hills
area with his wife Carolyn Pruett and
their two daughters.
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