Neuromodulation works by either actively stimulating nerves to produce a natural biological response or by applying targeted pharmaceutical agents in tiny doses directly to site of action.
Neurostimulation devices involve the application of electrodes to the brain, the spinal cord or peripheral nerves. These precisely placed leads connect via an extension cable to a pulse generator and power source, which generates the necessary electrical stimulation. A low-voltage electrical current passes from the generator to the nerve, and can either inhibit pain signals or stimulate neural impulses where they were previously absent.
In the case of pharmacological agents delivered through implanted pumps, the drug can be administered in smaller doses because it does not have to be metabolized and pass through the body before reaching the target area. Smaller doses—in the range of 1/300 of an oral dose—can mean fewer side effects, increased patient comfort and improved quality of life.
Most frequently, people think of neuromodulation in the context of chronic pain relief, the most common indication. However, there are a plethora of neuromodulation applications, such as deep brain stimulation (DBS) treatment for Parkinson’s disease, sacral nerve stimulation for pelvic disorders and incontinence, and spinal cord stimulation for ischemic disorders (angina, peripheral vascular disease).
Spinal cord stimulation
Stimulation does not eliminate the source of pain, it simply interferes with the signal to the brain, and so the amount of pain relief varies for each person. Also, some patients find the tingling sensation unpleasant. The goal for spinal cord stimulation is a 50-70% reduction in pain. However, even a small amount of pain reduction can be significant if it helps you to perform your daily activities with less pain and reduces the amount of pain medication you take. Stimulation does not work for everyone. If unsuccessful, the implant can be removed and does not damage the spinal cord or nerves.
Some SCS devices use a low-frequency current to replace the pain sensation with a mild tingling feeling called paresthesia. Other SCS devices use high-frequency or burst pulses to mask the pain with no tingling feeling. A paresthesia-free setting is an option on most devices.
Stimulation does not eliminate the source of pain. It simply changes the way the brain perceives it. As a result, the amount of pain relief varies for each person. The goal for SCS is a 50 to 70% reduction in pain. However, even a small amount of pain reduction can be significant if it helps you perform daily activities and reduces the amount of pain medication you take. SCS does not improve muscle strength.
Intrathecal Pump Therapy
The fluid filled space around your spinal cord is called the subarachnoid or intrathecal space. Cerebrospinal fluid (CSF) flows through this area, bathing and protecting your brain and spinal cord. An intrathecal drug pump works more efficiently than oral medication because it delivers medicine directly into the CSF, bypassing the path that oral medication takes through your body. In fact, you generally need about 1/300 the amount of medication (morphine or baclofen) with a pump than when taken orally.
The pump is a round metal device about the size of a hockey puck that is surgically implanted beneath the skin of your abdomen. A small plastic tube, called a catheter, is surgically placed in the intrathecal space of the spine and is connected to the pump (Fig. 1). A space inside the pump called the reservoir holds the medication.
The pump is programmed to slowly release medication over a period of time. It can also be programmed to release different amounts of medication at different times of the day, depending on your changing needs. The pump stores the information about your prescription in its memory, and your doctor can easily review this information with the programmer. When the reservoir is empty, the doctor or nurse refills the pump by inserting a needle through your skin and into the fill port on top of the reservoir.
This therapy is completely reversible if you should ever decide to have the pump removed.