What is a Neurostimulator?
Neurostimulators are cardiac pacemakers-like devices used to
deliver electrical impulses to the central or peripheral nervous system.
Electrodes can be placed in the epidural space for spinal cord stimulation or in
the thalamus for deep brain stimulation. In addition, Nervion's IPG system may
also be used for urinary incontinence, baroreceptor stimulation (hypertension)
or for gastric stimulation related to gastroparesis and morbid
obesity.
Neurostimulator devices are constantly being upgraded with the focus being upon less
invasive approaches and longer lasting effects. Once a neurostimulator is placed
it is important to note that current models will need revisions every 3 to 5
years.
Pain Control using Neurostimulation
Neurostimulation delivers low
voltage electrical impulses (stimulation) to a specific target nerve in the
spinal cord or peripheral nerve to block the perception of pain. One popular
theory, the Gate Control Theory of pain developed by researchers Ronald
Melzack and Patrick Wall, theorizes that electrical neurostimulation of nerves
activates the body's pain inhibitory system. Therefore, this theory proposes
that there is a gate in the spinal cord that controls the transmission of pain
signals to the brain which results in pain relief. The theory explains that the
body can inhibit these pain signals by “closing the gate" and activating certain
non-noxious nerve fibers in the dorsal horn of the spinal cord. The
neurostimulation system composed of an IPG and electrodes implanted in the
epidural space, activates these pain-inhibiting nerve fibers and suppressing the
sensation of pain and replaced with a tingling sensation called paresthesia1,2
in the targeted pain area.
Neurostimulation may be an
alternative treatment to surgery for the management of certain chronic pain
conditions, including: Failed Back Syndrome, Complex Regional Pain Syndrome, and arachnoiditis.
1Melzack
R, Wall PD. Pain mechanisms: A new theory. Science. 1965; 150(699):971-9.
2Shealy CN, Mortimer JT, Reswick JB. Electrical inhibition of pain
by stimulation of the dorsal columns: Preliminary clinical report. Anesth Analg.
1967; 46(4):489-91.
Neurostimulation or Neuromodulation Therapy
The objective of neuromodulation
is to decrease pain rather than completely eliminate pain. A multitude of
scientific information confirms that the therapy is effective when used on
carefully selected chronic pain patients. These clinical studies summarize the
following therapeutic benefits as follows:
- An increase in pain relief (a
majority of patients may experience at least 50 percent reduction in pain)1,2,3
- Increase activity levels1,2,3,4
- Reduction of use of potent pain
killer medications2,3,4
Neuromodulation therapy may lead
to reduced hospitalizations and surgical procedures, thereby reducing health
care costs for the treatment of chronic pain, greater freedom to live a normal
life, and improved quality of life.2,3,4
1Burchiel K, et al. Prospective, multicenter study of spinal cord
stimulation for relief of chronic back and extremity pain. Spine.1996;
21(23):2786-2794.
2North R, et al. Failed back surgery syndrome: 5-year follow-up
after spinal cord stimulator implantation. J Neurosurg.1991; 28 (5):
692-699.
3North R, et al. Spinal cord stimulation for chronic, intractable
pain: experience over two decades. J Neurosurg.1993; 32 (3): 384-395.
4Racz G, et al. Percutaneous dorsal column stimulator for chronic
pain control. Spine.1989; 14 (1): 1-4.
Implantation Procedures
IPG's may be indicated for spinal cord stimulation to treat
intractable pain can be performed as a major neurosurgical procedure with
open laminotomy or as a minor surgery with placement of the neurostimulator by
an anesthesiologist or surgeon. The extent of local scarring, difficulty of
placement and available expertise determines which procedure is to be used.
Stimulation Parameter Adjustments
After a neurostimulator is placed, it can be adjusted for intensity of signal
and coverage pattern. Some aspects of this adjustment are left to the patient
and some are controlled by the physician. Tiny electrical
leads are placed at the end of a wire, which in turn is connected to a generator
box that determines signal strength and distribution. The generated signal is
sent to the underlying spinal cord and causes mild regional paresthesias that
can effectively block intractable pain signals from damaged nerves. Although
this can be effective solitary treatment, it is best seen as part of an overall
treatment regimen, including pharmacological, psychological and social
interventions.
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