Neurostimulation (Spinal Cord and Peripheral Nerve Stimulation)

Both the spinal cord and peripheral nerves can be stimulated by implanted electrodes in a manner which reduces chronic pain from spinal disease, peripheral nerve injuries, occipital headaches, diabetes, RSD, etc.  Neurostimulation (NS) can also be used to treat vascular disease by increasing blood flow to the extremities, intractable angina   pain, and as a treatment for intractable urinary incontinence.

Spinal cord stimulation works by causing a rapid frequency electrical signal to activate the posterior part of the spinal cord, closing “gates” to painful impulses coming up from below.  Thus, for most foot, leg, and low back pain, the leads are implanted in the epidural space in the thoracic region of the spine.  Arm and hand pain require implantation in the upper cervical part of the spine.  Pelvic pain and urinary incontinence are treated by implantation of the leads in the sacral spine (near the tailbone).

Patients who have chronic pain conditions that have failed treatment by several other more conservative measures including physical therapy and injections may be candidates for NS.  In some cases, NS is the only therapy that will be effective for pain control.  After several other more conservative measures have been used, if the patient has the proper psychological profile, they may be considered for a NS trial.  In almost all cases a trial stimulation period precedes any permanent implantation.  Trial leads are usually placed as an outpatient under mild or no sedation using only local anesthesia.  It is necessary for the patient to be conversant during the part of the trial lead placement in which the stimulation pattern is to be determined.  The number and type of leads are dependent on the location of pain.  Low back pain requires two leads as does one arm-one leg pain.  Occipital headaches may require one or two leads while pelvic stimulation or incontinence may require four leads.  Most trial leads are round leads placed through a needle.  The epidural space is used for spinal cord stimulation, the sacrum for pelvic stimulation and for incontinence, and the back of the head is used for occipital stimulation.   These leads are placed as an outpatient procedure, afterwhich the patients use a trial stimulator box for 1-2 weeks to test the degree of pain relief during different activities.  If the pain relief is greater than 50% and there are no untoward complications during that period, the trial leads are removed (come out very easily), and the decision is made to implant permanent leads.  There are two different permanent NS systems available: IPG (implantable programmable generator) and RF.  The IPG system is entirely internal with the leads, extension wires, stimulator, and batteries all under the skin.  The RF unit uses rechargeable batteries placed in an external control unit and uses radiofrequency (RF) energy to transmit the battery power to a receiver on the other side of the skin.  Advantages of the RF unit are no surgical replacement of the generator is necessary and more power.  Disadvantages are inability to use the RF unit in the shower and minor inconvenience.  Advantage of IPG is complete concealment.  Disadvantage is limited battery life necessitating another expensive generator/battery unit must be surgically implanted every 2-5 years, and low power.

Your physician will speak with you about which unit would be appropriate for you.

Once the decision has been made to implant permanently, the decision on type of lead becomes important.  For the vast majority of patients, a round lead system exactly the diameter of the trial leads is appropriate.  However, there are other leads that require a laminotomy (removal of part of the bone of the spine).  In any case, the leads must be secured to a structure that does not move much in order to keep the lead tip from moving.  With spinal cord stimulation, the leads are sutured to the spine ligaments while with dorsal root ganglion stimulation, they are secured to the ligaments of the tailbone.  The implantation is therefore a surgical procedure carried out under sterile conditions in a hospital or surgery center suite.   After implantation, for several weeks, you may be instructed to avoid certain positions or activities in order to allow time for fixation of the leads to surrounding tissues to occur.  Generally, there will be two or three small incisions made for the permanent implantation.  For the IPG system, activation is immediate while for the RF system, approximately 7-10 days is allowed to elapse before activation.  Once the system is activated, there will be a mild tingling sensation in the target area over the painful sites.  The degree of this sensation can be instantaneously adjusted by your electronic control at home.  Many patients turn their units off at night since their pain is markedly less.

Implantation of the leads is usually relative easy, however there are occasional patients that require extensive lead manipulation and special techniques for placement.  DRG lead implantation as shown below can sometimes be difficult as can sacral nerve stimulation.  Occipital nerve stimulation and other peripheral nerve stimulation provides a unique opportunity to directly stimulate pain transmitting nerves.  This can be very successful.  Overall, the NS systems decrease pain long term with an increase in patient function. The success rate for those completing 4 years according to Neurosurgery  2001 May;48(5):1056-64 was successful SCS (>50% reduction in pain for 1 yr) occurred in 83.3% of patients with nonspecific leg pain, 89.5% of patients with limb pain associated with root injury, and 73.9% of patients with nerve neuropathic pain.  The study had a 4 year followup period.

Other similar success rates have been reported for interstitial cystitis, lower extremity peripheral vascular disease, angina, occipital nerve stimulation.  Slightly lower values (62%) are reported for urinary incontinence treatment.

Complications are lead migration, battery/generator failure (IPG only),  infection (rare), neurologic injury (extremely rare).

 

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