Pacemakers for Pain

Author: 
Dr. Robert Valentz, Alaska Spine Institute

Pain that lasts for longer than six months is generally defined as chronic pain. For those suffering from chronic back or limb pain, spinal cord stimulation (SCS) may provide new hope.

Spinal cord stimulators are battery-powered devices that are surgically implanted beneath the skin. Sometimes called “pacemakers for pain” spinal cord stimulators deliver low levels of electrical energy directly to nerve fibers. This direct approach to treating pain at its source can be very effective. While not considered a cure for pain, the objective of this therapy is to reduce chronic pain to a manageable level, helping the patient to resume a more normal lifestyle.

Chronic pain is often the result of a trauma, injury, disease or other nervous system disorders. Frequently, more than one treatment or therapy is required to treat chronic pain. When those treatments are not successful or if surgery or further surgery is not recommended, SCS may be an option.

Screening
A patient’s qualification for SCS depends on diagnosis, medical history and the type or severity of pain. Spinal cord stimulators are not used to treat pain which is likely to get better with time -- often characterized by deep aches, throbbing or sore muscles. SCS is appropriate therapy for patients suffering from the following types of chronic pain:
• Pain resulting from failed back surgery syndrome
• Neuropathic (nerve) pain which is characterized by burning, severe shooting pain and/or numbness and tingling sensations
• Chronic pain from sciatica or pain that radiates along the sciatic nerve due to a compression or pinch a spinal nerve

Careful screening of patients greatly improves the chance for successful outcome with SCS. Screening involves identifying the cause, type, severity and location of pain. Medical, family and work history is also important as is a patient’s ability and receptiveness to learn about the therapy and follow doctor’s orders. All previous treatments that relate to the pain are reviewed and the screening may include a psychological evaluation.

Trial Stimulation
Prior to placing a spinal cord stimulator, the patient typically undergoes a period of trial stimulation to assess the effectiveness of stimulation in providing pain relief in their specific case. The placement of the electrode is performed under local anesthesia. Electrodes are placed over the back of the spinal cord and connected to a battery-powered pulse generator device. The stimulator is programmable so that the signal can be adjusted by the patient for optimal pain relief. Recipients are educated extensively on the use and programming of their device.
SCS stimulation effectively changes normal pain messages and replaces them with a more pleasant sensation called paresthesia. If a patient responds well to the stimulation and pain is relieved, then spinal cord stimulation is considered a good option. For some patients, however, if the pain is not relieved the temporary electrode is removed.

How does it work?

The current theory is that the electrical current input of SCS alters the spine’s processing of the pain, preventing pain signals from reaching the brain. Electrical signals are passed from an electrode directly to nerve fibers. Typically, patients report that the pain is replaced by a tingling feeling or a sensation of warmth. SCS systems typically consist of three components designed to work together:
• Leads
• Generator/receiver
• Programmer/transmitter

Leads
Leads are very thin wires or cables. One end of the lead is connected to the implanted generator or receiver, and the other end is placed near the nerve fibers that are to be stimulated. The end near the nerve fibers has metal electrodes that can deliver mild electrical impulses. Percutaneous leads (implanted through a needle) are almost always used for trial stimulation. Surgical leads are larger and require a surgical laminotomy. Either percutaneous or surgical leads can be used for permanent implantation.

Each lead has anywhere between four and eight electrodes. The number of electrodes used depends upon the condition being treated as well as the physician’s preference. For example, more complex pain patterns, such as those involving more than one area and more than one extremity (arms and/or legs), involve more nerve structures. Additional electrodes are often required to stimulate all of these structures.

Generator/Receiver
Three types of SCS systems are available for spinal cord stimulation. The first is a conventional implantable pulse generator (IPG) which is powered by a battery housed in a single metal container and implanted under the skin. The IPG is connected to a lead or leads that are placed over the spinal cord. One disadvantage to this system is that an IPG must be surgically replaced when its battery runs out.

Most batteries for IPGs generally last three to five years, although extensive stimulation may shorten battery lifespan. To address this, a second and alternate option is a rechargeable implantable pulse generator (rechargeable IPG). Also implanted under the skin, the rechargeable IPG’s battery is -- rechargeable. Even a rechargeable IPG will eventually reach a point when its battery fails to hold a practical charge. When this happens, it is necessary to replace the rechargeable IPG in a surgical procedure.

Lastly, a radio frequency system (RF) consists of a power source in two parts: a receiver, which is implanted under the skin, and a transmitter, which is worn outside the body like a cell phone or pager. The transmitter, which contains an antenna, electronics, and a replaceable or rechargeable battery, delivers radio waves through the skin to the implanted receiver. The receiver then sends the electrical impulses to the lead(s).

Programmer/Transmitter
A programmer and transmitter are devices used to program an SCS system and to adjust the intensity of the stimulation. Programs are the various electrical settings (amplitude, frequency, pulse width, and polarity) that are transmitted to each electrode on the lead. An external programmer/transmitter allows a physician to create as many programs as is necessary for a patient’s pain patterns. It also allows patients to choose the best program for their pain as it changes throughout the day.

At Alaska Spine Institute, physicians who specialize in back pain and other chronic pain problems use the most up-to-date advancements in the diagnosis and treatment of each patient. ASI has state-of-the-art equipment and a highly trained and experienced team of physicians and support staff. This facility is focused on interventional spinal procedures and interventional pain management and can determine if spinal cord stimulation, or some other approach, is best for your individual situation. For an evaluation, call us at (907) 563-8876 or visit www.alaskaspineinstitute.com.