CHRONIC BACK PAIN
Neuromodulation and Drug Delivery Systems
- a Reversible Option
Chronic back and/or leg pain is a condition described as pain that is
felt in the back and/or leg that may result from spinal diseases including:
arachnoiditis, degenerative disc disease, epidural fibrosis, failed back
syndrome, lumbar disc herniation, osteoporosis, and spinal stenosis. Back
pain is often located in the lower back, but it may extend to other areas,
such as the thighs, calves, and feet. Affected areas may feel tender or
sore to the touch, and the pain may increase with movement. This type
of pain can be felt as sharp or knife-like pain, a burning sensation,
or as a dull muscular ache. Symptoms can range from mildly uncomfortable
to completely disabling.
When pain persists (or recurs) for more than six months, it is said to
be chronic and normal activities can become severely restricted or even
impossible. Chronic pain may stem from an initial injury that has long
since healed. Or, it may have an ongoing cause such as arthritis, cancer
How do you register pain?
When you feel pain, it is really a reaction to signals that are transmitted
from the site of pain. These signals are sent from the pain source, through
the nerves in the spinal cord, to your brain, where you perceive them
Neuropathic pain is caused by damage to nerve tissue. It is often felt
as a burning or stabbing pain. One example of neuropathic pain is a pinched
Nociceptive pain is caused by an injury or disease outside the nervous
system. It is often an ongoing dull ache or pressure, rather than the
sharper, trauma-like pain more characteristic of neuropathic pain. One
example of nociceptive pain is cancer pain.
Chronic pain often produces various harmful psychosocial effects including
fear, anxiety, interference with work, decreased self-esteem, and problematic
relationships. The physical effects of pain can include increased heart
rate and blood pressure, increased blood sugar, decreased digestive activity,
and reduced blood flow.
Is Your Pain Treatment Working for You?
Many different treatments may be used to manage chronic pain. Common
pain medications include mild pain relievers, such as aspirin, weak opioids,
such as codeine, and strong opioids, such as morphine. Pain can sometimes
be difficult to control and can get in the way of daily activities for
you and your family. If your current treatment is not providing enough
pain relief, or is causing uncomfortable side effects talk to your doctor.
He or she may be able to adjust your medication dosage, prescribe a different
medication to reduce side effects, or offer you other options, such as
neurostimulation and/or intrathecal drug delivery.
Pain Therapies which include intrathecal drug delivery and neurostimulation,
are proven, effective treatment alternatives when other pain treatments
provide unsatisfactory relief. Results may vary depending on the patient.
Intrathecal drug delivery and neuromodulation work directly on the spinal
cord, which is the highway for pain signals. These therapies are thought
to work by interfering with pain signals before they reach the brain.
They can offer good to excellent pain relief, and improve your ability
to go about daily activities.
Overview of Indications
The etiology and pattern of the patient pain guide the selection of
the appropriate Pain Therapy. Neurostimulation is indicated to aid in
the management of chronic intractable pain of the trunk or limbs. In general,
neurostimulation is used for neuropathic pain. Examples of neuropathic
pain syndromes that typically respond well to neurostimulation are shown
in Figure 1.
Nociceptive or somatic pain, pain in multiple or axial sites, and even
pain with a changing pattern are better suited to intrathecal drug delivery.
Pain syndromes that are typically most opioid responsive also appear in
Figure 1: Indications for Medtronic
The intrathecal drug delivery system
offers a fully implantable and programmable method of continuous
drug delivery. In use clinically since 1982, and commercially since
1988, the programmability of the system allows the following:
- Dosages to be varied throughout the day and tailored to match
your individual medication needs.
- The potential for a lower dose (compared to oral drugs), which
may result in reduced side effects.
- Non-invasive dose changes.
This device has been available for many years, and has been implanted
in more than 50,000 patients worldwide. It is a totally implantable
and programmable system, which consists of two parts - the catheter
and the pump - that are both placed inside the body during an operation.
The physiology of pain begins with sensory neurons called nociceptors.
A pain message is transmitted along these neurons to the dorsal horn of
the spinal cord. In the dorsal horn, sensory neurons release several neurotransmitters
that act on the dendrites of ascending neurons. Eventually, these ascending
neurons carry the signal to the brain where it is perceived as pain. One
of the key neurotransmitters in pain transmission is substance P. Opioids
inhibit the release of substance P and other neurotransmitters by bonding
to opioid receptors (e.g., morphine binds to Mu, Kappa and perhaps Delta
receptors1). This, in effect, blocks the message before it reaches the
brain and is perceived as pain.
Intrathecal drug delivery utilizes a small pump that is surgically placed
under the skin in the abdomen. A pain relieving drug is contained inside
the pump, and is delivered through a small, soft tube called a catheter,
directly into the area surrounding the spinal cord (intrathecal space).
The spinal cord is like a highway for pain signals on their way to the
brain, where the feeling of pain is experienced by your body. As the pain
relieving drug is delivered directly to the spinal cord where these pain
signals travel, intrathecal drug delivery can offer significant pain control,
with much lower doses of medication than would be required with pills.
This helps to minimize side-effects that often accompany other treatments.
An intrathecal drug delivery systems are composed of two implantable
components: an infusion pump and an intraspinal catheter. The pump is
placed abdominally in a subcutaneous pocket, while the catheter is inserted
into the intrathecal space of the spine, tunneled under the skin and connected
to the pump. Medication can be delivered at constant or variable flow
Implantable pumps are battery-powered devices that store and dispense
drugs according to instructions received from a programmer.
The pump contains a reservoir, reservoir fill port, and an optional
catheter access port.
- Reservoir: The reservoir is the cavity inside the pump where
the medication is stored.
- Reservoir Fill Port: In the center of the pump is a raised
area (called a "port") that is used for filling and
emptying the pump. In the middle of this port is a self-sealing,
silicone septum that is used during your pump refill procedure.
- Catheter Access Port: Most pumps feature a catheter access port.
The catheter access port allows doctors to bypass the pump reservoir
and send medications or sterile solutions directly into the implanted
catheter. Doctors also may use the catheter access port for some
diagnostic purposes, such as testing to ensure medication is able
to flow through the length of the catheter.
The catheter is a flexible, silicone tube that connects to your
pump and delivers medication from the pump to a specific site in
your body. Your doctor trims the catheter to the appropriate length
for your body size.
Your doctor or nurse will use a programmer during your refill
and checkup sessions. This programmer allows your doctor or nurse
to communicate with and program your implantable pump.
Attached to the programmer is a component known as the "programming
head." The programming head looks similar to a computer mouse.
Instructions for rate and dose adjustments are transmitted through
the programming head to the pump by radio signals. The two-way radio-frequency
link also allows the programmer to receive information from the
pump. This painless interchange of information between the programmer
and pump is called telemetry.
Catheters used with the SynchroMed® pump.
Benefits of an Implantable, Programmable
A totally implantable system may reduce the risk of infection compared
to the long-term use of external systems.1 Because there are no external
parts, the system usually does not restrict daily activities. A programmable
pump allows clinicians to adjust doses non-invasively, minimizing patient
discomfort. In addition, the pump can be programmed to deliver different
doses at various times of the day--meeting patients' changing needs.
How effective is intrathecal drug delivery?
Intrathecal drug delivery has been shown to provide effective pain relief
in 60–80% of patients. In addition, it has been shown to improve
patients overall mood, as well as reducing the need for additional pain
medications. This has helped many patients with severe pain improve their
quality of life and participate more fully in daily activities, in many
cases enabling patients to return to work.
Chronic pain is a common problem, affecting over 10% of the adult population
worldwide. Although common pain medications or other types of treatment
such as physiotherapy can provide adequate pain relief in many patients,
this is not always the case. For people whose pain treatment is no longer
effective, or which causes uncomfortable or unpleasant side-effects, neurostimulation
may help to increase pain relief and comfort, whilst also improving quality
of life. Neurostimulation has been used to treat chronic pain since the
early 1970s. Currently, approximately 15,000 patients a year are treated
with neurostimulation around the world.
Neurostimulation is an effective alternative to repeated back surgery,
medication or other therapies. Neurostimulation has been shown to provide
effective pain relief. Patients who have success with neurostimulation
usually experience a 50–88% reduction in their pain and improved
ability to participate in daily activities. Neurostimulation can also
reduce or eliminate the need for additional pain medications and further
To date, over 100,000 people worldwide have received neurostimulation
systems for pain, with the first being introduced in 1967. Medtronic introduced
programmable implantable neurostimulation systems in the U.S. in 1980
and now offers both fully implantable systems and an external radiofrequency-powered
What is neurostimulation and how does it
Neurostimulation uses a small system that is surgically placed under
the skin to send precisely controlled mild electrical impulses (which
are felt as pleasant tingling sensations) to your nervous system. These
electrical impulses are delivered through a lead (a special medical wire
or thread), that is also surgically implanted. The electrical impulses
block the pain signal from reaching the brain, thereby alleviating the
Neurostimulation delivers low voltage electrical stimulation to the spinal
cord or targeted peripheral nerve to block the sensation of pain. One
theory, the Gate Control Theory of pain developed by researchers Ronald
Melzack and Patrick Wall, proposes that neurostimulation activates the
body's pain inhibitory system. According to this theory, there is a gate
in the spinal cord that controls the flow of noxious pain signals to the
brain. The theory suggests that the body can inhibit these pain signals
or "close the gate" by activating certain non-noxious nerve
fibers in the dorsal horn of the spinal cord. The neurostimulation system,
implanted in the epidural space, stimulates these pain-inhibiting nerve
fibers, masking the sensation of pain with a tingling sensation (paresthesia).
As neurostimulation works in the area where pain signals travel, electrical
impulses can be directed to cover the specific areas where you are feeling
pain. Neurostimulation does not involve any medication, so there are very
few of the side effects that often accompany other treatments.
Neurostimulation may be the appropriate treatment for the management
of certain chronic pain conditions, including: Failed Back Syndrome (FBS),
Complex Regional Pain Syndrome (CRPS), and arachnoiditis.
Benefits of Neurostimulation
The goal of neurostimulation is to reduce rather than eliminate pain.
Published studies of the therapy have shown that when used on carefully
selected chronic pain patients, neurostimulation may:
- Improve pain relief (a majority of patients may experience at least
50 percent reduction in pain)
- Increase activity levels
- Reduce use of narcotic medications
These results may also lead to reduced hospitalizations and surgical
procedures, reduced health care costs, greater independence, and improved
quality of life.
Patient Selection Criteria
Adherence to patient selection criteria is critical to long-term success.
Experience has shown that these therapies work best in a carefully selected
patient population. Here are seven patient selection criteria as published
by Elliot Krames M.D., in The Journal of Pain and Symptom Management (J
Pain & Symptom Mgt.,1996):
- More conservative therapies have failed
- An observable pathology exists that is concordant with the pain complaint
- Further surgical intervention is not indicated
- No serious untreated drug habituation exists
- Psychological evaluation and clearance for implantation has been obtained
- No contraindications to implantation exist
- A Screening test has been successful
Screening Test Period
The next step is the screening test period. This period of trial stimulation
- Evaluation of the impact of stimulation on the patient’s pain
and daily life
- A low-cost means of evaluating the effectiveness of the therapy
- Exclusion of non-responding patients prior to system implantation
- Identification of lead position and stimulation parameters
- A method of demonstrating efficacy to both third-party payers and
The screening test period is an opportunity for the patient to develop
an understanding of the technology and realistic expectations of the therapy.
During this time the patient is carefully educated and encouraged to try
different parameter settings to optimize and fully "test" neurostimulation.
At the end of the screening test period, patients return to the physician's
office for an assessment of their experience with the therapy. Each of
the following questions should be addressed:
- Did the stimulation continue to "cover" the painful area
- Was the paresthesia an agreeable sensation?
- Did the paresthesia relieve the patient's pain during activities
which typically provoke pain?
- What percentage pain relief was achieved with stimulation? (Was it
50 percent or greater?)
- Was the patient capable of understanding the technology and operating
If the patient does not respond positively to neurostimulation during
the screening test period, the lead is removed. If the patient responds
positively to a neurostimulation system during the test period, a complete
neurostimulation system is implanted.
- Fully Implanted System
The fully implanted neurostimulation system consists of an implantable
neurostimulator, an implantable lead and extension, a programmer
used by physicians, a patient programmer or an external control
magnet that turns the system on or off.
The implantable neurostimulator is the device that generates the exact
electrical impulses that are sent to your spinal cord to control your
pain. The neurostimulator contains a special battery and electronics to
create these impulses. The device is most frequently placed under the
skin in your abdomen.
Neurostimulation leads are special insulated wires designed to deliver
neurostimulation to the spinal cord. A neurostimulation system may use
one lead (single-channel) or two leads (dual-channel). The lead is about
28cm long and is placed under the skin near your spine. It contains a
set of electrodes through which the electrical stimulation is delivered
to the spinal cord.
The extension is a small cable about 51cm long that is placed under the
skin and connects the lead to the neurostimulator used by physicians.
Programmer Used by
The programmer lets your doctor adjust your neurostimulation system
to the appropriate level for your pain. This programmer consists
of a computer, programming head, and a printer. The programming
head is placed over the area where the neurostimulator is implanted
to program the settings by use of radio waves. This procedure is
done through the skin and is generally considered to be painless.
When you visit the doctor’s office, your neurostimulation
system can be reprogrammed to more effectively deal with your pain.
For example, the multiple electrodes on leads can be readjusted
to provide differing patterns of pain coverage. The strength of
the pain coverage can be altered to accommodate lesser or greater
Programmer used by physicians
The hand-held patient programmer allows you to program your own
stimulation (within the settings your physician has selected. The
patient programmer allows you to adjust the stimulation according
to your pain between visits to the doctor’s office. Depending
on your need for pain control, you can use the patient programmer
to turn your system off and back on. You can also direct your system
to provide greater or lesser pain relief (by increasing or decreasing
the tingling), within limits set by your doctor. You will not be
able to change those limits on your own, but you may discuss the
need for possible changes with your doctor. A 9-volt battery is
required to operate the programmer.
Programmer used by patients
Neuromodulation and Intrathecal Drug Delivery are two options available
to patients with chronic pain. The benefit of these therapies are:
- The therapies are safe with very few complications.
- It is very effective in relieving pain.
- Effective in improving function.
- The therapy is totally reversible (i.e. non-destructive).
- The implanting technique is minimally invasive
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