Overview of Nerve Stimulation
Nerve stimulation, also known as Peripheral Nerve Stimulation (PNS), is a method that focuses on managing chronic pain conditions and has been used since the early 19th century. The first official medical study using this method wasn’t conducted until 1976 by a team of researchers led by Campbell.
After that, PNS has been considered a frequent treatment option for managing chronic pain conditions. Chronic pain includes different types, like persistent lower back pain, neck pain, and nerve-related pain due to different health conditions, such as causalgia (severe burning pain), diabetic neuropathy (nerve damage caused by diabetes), and chronic regional pain syndrome.
Many people suffer from these types of chronic pain and this causes significant economic strain on society. In fact, these health issues are noted as the primary reasons for disability worldwide. At the moment, the United States is facing an opioid crisis, with over 15,000 deaths linked to prescription opioids being reported in 2015.
Moreover, managing chronic pain with conventional medications can lead to complications due to multiple drug interactions, possibly resulting in unbearable side effects. That’s why PNS is an important treatment option. It generally offers safer and more effective relief for such chronic pain conditions.
Anatomy and Physiology of Nerve Stimulation
When trying to offer relief from pain in specific parts of the body, the nerve that sends signals to that area is stimulated. This stimulation can be achieved either through electricity or magnets. Here’s a look at how they both work:
Electrical Nerve Stimulation:
While the exact understanding of electrical nerve stimulation is still unclear, it’s broadly based on something called the “gate control theory.” Here’s a simple way to understand it: our body has different type of nerve fibers – some carry painful signals, and others carry non-painful ones. With electrical stimulation, the non-painful fibers (named as A-beta fibers) are excited, which tends to block the painful signals sent by different fibers known as C-fibers. This is often seen as “closing the gate” for discomfort in the spinal cord, allowing for relief from discomfort. There are also other suggested modes of action, such as releasing certain inhibitory chemicals to reduce hyperactivity of other nerves or stimulating the release of substances like serotonin, adenosine, and noradrenaline, which might help to alleviate pain.
Magnetic Nerve Stimulation:
Just like electrical nerve stimulation, magnetic nerve stimulation also offers relief from discomfort, but in a different manner. Case in point: the Transcranial Magnetic Stimulator. This device, which isn’t implanted into the body, uses a capacitor to generate a magnetic field. When the device is used on the skull, the magnetic field can stimulate neurons in the brain, leading to potential therapeutic effects, such as affecting brain chemicals, increasing blood flow in the brain, or reducing oxidative stress on neurons.
For the purpose of our discussion, we will be focussing on implanted electrical nerve stimulators, offering a detailed understanding of how they work in the following sections.
Why do People Need Nerve Stimulation
Peripheral nerve stimulation (PNS) is a treatment method that controls the amount of energy in your body using a targeted electric current. It has been used to successfully manage long-term pain disorders. In the past, PNS has shown great results when used on various nerves in the body including nerves in the arms, legs, and groin.
For example, there was a treatment where a PNS lead, a kind of electrical charge, was used for the first time to manage a type of headache called occipital neuralgia. In another study, a group of patients were treated for a type of severe headache called a cluster headache with a specific type of stimulation called sphenopalatine ganglion (SPG) stimulation. The results showed that it helped about 67% of subjects to feel less pain and reduced episode frequency for 36% of patients.
Another type of nerve stimulation, called occipital nerve stimulation (ONS), has been used for treating migraines. In a study, it was found that 39% of patients experienced fewer headaches each month after receiving this treatment. It may also be effective for other types of headaches.
Research has also found PNS effective in treating pain in the lower back joint (sacroiliac joint). A year after the treatment, patients reported improvements in pain and functionality using three different assessment tools: the International Patient Satisfaction Index (IPSI), Visual Analog Scale (VAS), and the Oswestry Disability Index 2.0 (ODI). Similar improvements were noted in another study for shoulder pain related to a condition called subacromial impingement syndrome.
A recent study showed PNS being effective in treating lower back pain. The treatment involved stimulating specific spinal nerves for 30 days. Individuals reported significant decrease in both average and extreme pain intensity at the end of the trial, with continuing benefits seen at four months and even up to a year after treatment.
On top of those treatments, PNS was also found effective in treating facial pain after a stroke by using a type of stimulation called Gasserian ganglion stimulation.
When a Person Should Avoid Nerve Stimulation
There are certain situations when the procedure of inserting a stimulator lead (a kind of wire that sends electrical signals to the body) can’t be done. For example, if there’s an infection at the spot where the lead would be inserted, we can’t do the procedure.
Also, if a person has a bleeding disorder that’s currently active, we have to be very careful. A bleeding disorder can make it hard to stop bleeding once it starts, and this could cause a hematoma (a swelling filled with blood) to form during or after the procedure. So, we have to evaluate the risks before going ahead with the procedure.
Equipment used for Nerve Stimulation
Peripheral nerve stimulation (PNS) is a procedure that requires a special kit containing a needle for transmitting signals and an electrode or device that provides electrical stimulation. The patient is prepared in a clean, sterile environment. To clean the skin, a solution of chlorhexidine or iodine is used, and a sterile cloth is applied over the surgery area. Doctors then choose a specific point where they will insert the needle and give local anesthesia to numb the area.
An ultrasound is used to locate the target nerve before using a needle – referred to as a transducer needle – to reach it. The electrode is introduced through this needle, positioning it approximately 1 cm away from the nerve. Once it’s in place and connected to a battery, doctors test the electrode during the surgery to make sure it causes a tingling sensation (paresthesia) in the area where the patient usually experiences pain. If it works as expected, the electrode is placed under the skin and kept in place by a stitch.
Alternatively, a surgeon, typically a neurosurgeon, may choose to expose the nerve by directly exploring the area around the nerve. In this approach, the electrode is placed directly on the nerve.
In recent years, scientists have started developing wireless nerve stimulation devices that eliminate the need for an implanted device that generates pulses. Wireless devices have built-in microelectrodes within an implantable electrode. The stimulation for these microelectrodes comes from an outside source, like a patch or wearable device. In the U.S., the Food and Drug Administration (FDA) has approved four such devices for wireless PNS.
Who is needed to perform Nerve Stimulation?
A peripheral nerve stimulator is a device that’s placed under your skin by certain types of doctors to help with pain. It’s usually done by a neurosurgeon (a doctor who specializes in surgery on the nerves and brain), an anesthesiologist who’s specially trained in pain management (a doctor who helps control your pain and puts you to sleep for surgery), or an interventional radiologist (a doctor who uses imaging like X-rays to guide minimally invasive procedures).
It’s important that the doctor who places the stimulator has plenty of experience. They should have done this procedure several times under the guidance of a more experienced physician before they start doing it on their own. This ensures that they know how to do the procedure safely and effectively, so you get the best possible care.
Possible Complications of Nerve Stimulation
Like any other type of surgery, some common problems that can occur include infection, bleeding or the formation of a blood clot at the surgical site, pain at the place of surgery, and damage to nerves.
Problems specifically related to the surgical device used can also happen. These can include the device moving away from its intended location, a break in the device, and the device not working properly. While these issues are not usually serious, they may require a minor repeat procedure to correct the placement of the surgical device.
What Else Should I Know About Nerve Stimulation?
Chronic pain, or long-lasting pain, is a common health issue that affects a lot of people and can be a big strain on the economy and society. Given the ongoing problem with opioid misuse, it’s really important for us to find other ways to treat pain. One option is peripheral nerve stimulation, which is a fairly safe method for managing painful conditions.
This type of treatment can numb certain areas of the body without the patient having to take strong painkillers like opioids, which can often have unwanted side effects that impact the entire body. Because these nerve stimulation treatments are less invasive, or don’t require a big operation, they are a good alternative for patients who aren’t able to have major joint surgeries due to potential complications with general anesthesia.
