Barcelona, venue of the most awaited neuromodulation world event in 2022

Under the slogan “Neuromodulation: from scientific theory to revolutionary therapy”, Barcelona will host this coming May the 15th World Congress of the International Neuromodulation Society, the most important neuromodulation congress in the world.

Dr. Antonio Ojeda Niño, specialist in Anesthesiology and expert in Interventional Pain Treatment, will participate in this congress by giving a talk at a public education event to be held on May 21, in which he will speak on the efficacy of neuromodulation in the management of low back and extremity pain.

But what is neuromodulation? In the following lines, Dr. Ojeda Niño gives us a brief summary of this therapy and why it is important to know about it.

Neuromodulation is a therapy that consists of using devices that reversibly modify the activity of nerve tissues. This treatment improves the quality of life of several diseases, such as chronic pain, Parkinson’s disease, pelvic disorders (especially incontinence) and ischemic diseases such as refractory angina pectoris or peripheral vascular disease. These neuromodulation therapies can be performed using electricity (neurostimulation) or drugs (chemical neuromodulation).

Neurostimulation (Electrical Neuromodulation)

With advances in technology and a better understanding of how electricity acts on nerve tissues, new treatments have been developed that in recent years have improved the results of this therapy. Currently, neurostimulation is a consolidated therapy and one of the fastest growing sectors within medicine.

On the other hand, within neurostimulation we can differentiate between invasive and non-invasive therapy. The former requires devices to be placed inside the body and can be performed by administering electricity through cannulas (special needles) in a specific nerve (Pulsed Radiofrequency), or by implanting electrodes (wires) that stimulate a specific nerve tissue (implantable systems).

These electrodes can be placed in the brain (brain stimulation), near the spinal cord (spinal cord stimulation), around the peripheral nerves or near the dorsal root ganglion (small nodule formed by neurons located near the spinal cord). Today, the devices used are smaller and easier to fit, have longer-lasting and/or rechargeable batteries and are compatible with MRI scans, all of which have improved the experience of people using this therapy.

As for noninvasive neurostimulation techniques, the most common are transcranial magnetic stimulation (TMS) and transcutaneous electrical stimulation (TENS).

Spinal cord stimulation for pain management

Spinal cord stimulation has been used in pain management for more than 50 years and is mainly used to treat persistent pain that has previously not responded to other treatments (medication, physiotherapy, rehabilitation, infiltrations, etc). It is a reversible therapy that is placed through minimal surgical intervention.

In spinal cord stimulation, electricity is delivered near the spinal cord through electrodes (wires) that are placed in a space located in the spinal column around the spinal cord (the peridural space). The electrodes are connected to a special battery that generates energy and is implanted inside the body (generator or implantable neurostimulator). This energy produces an electrical field that modifies the activity of the spinal cord, transforming the message transmitted by the neurons to the brain, where that message is perceived as pain.

Numerous studies have shown that neuromodulation relieves pain in different problems, among them:

  • Persistent pain after spinal surgery (formerly called failed back syndrome).
  • Peripheral neuropathic pain (nerve pain).
  • Complex regional pain syndrome (formerly called reflex sympathetic dystrophy, Sudeck’s atrophy, etc.).
  • Pain due to lack of blood supply (ischemic pain) of the lower extremities.
  • Pain of peripheral nerve endings caused by diabetes (diabetic neuropathy).

Chemical neuromodulation

The administration of small doses of medication close to its area of action (fluid surrounding the spinal cord) provides potent effects and fewer systemic adverse events, e.g., morphine administered by this route is at least 100 times more potent than morphine administered orally. People who have chronic pain or muscle spasms and for whom medication causes side effects or the doses are not sufficient to control their symptoms, may benefit from this type of treatment.

Spinal therapy with implantable drug delivery systems

Spinal therapy is performed by placing a catheter (very small tube) in the space containing the liquid surrounding the spinal cord (intrathecal space), to deliver the medication to this area. Thus, the drug arrives directly where the nerve signals are transmitted, exerting its effect without the involvement of digestion (medications taken orally) or the bloodstream (injected medications). The catheter is connected to a perfusion pump containing a reservoir and implanted under the skin, which is filled with the drug(s) to be administered.

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The most commonly used drugs are opioids (morphine, hydromorphone), local anesthetics (usually bupivacaine), baclofen, clonidine and ziconotide. Each of these drugs has special properties and are used differently according to the needs of each person.

Injectable infusion pumps – variable and fixed flow

Variable flow pumps include a drug reservoir from which they automatically dispense a programmed amount of drug through a catheter. These pumps have a small built-in battery and integrated microelectronic circuitry to control drug delivery. The medication is adjusted quickly and easily with an electronic programmer that allows adjusting the amount, time of administration and mode of infusion of the drug, as well as alarms that warn when the pump reservoir should be refilled or when the battery is about to run out.

On the other hand, fixed-flow pumps are mechanically operated and are driven by a gas pressure chamber surrounding a flexible inner reservoir. When the gas in the pressure chamber is heated by body heat it expands, pressing the inner chamber to propel the drug through the catheter to the site of action in the body. Depending on the treatment needs, the drug dosage is adjusted to individual needs, making the operation of the device simple and safe. Changes in pressure or temperature have very little influence on the flow, ensuring that the device remains highly accurate under different conditions. In any case, the pump is designed for a long service life and operates without a battery.

Refills of the reservoir with medication are made depending on the needs of each patient (varies from 1 to 6 months). The reservoir is filled using a sterile needle inserted through the skin, a simple and painless procedure. However, this method must be performed by sufficiently trained personnel because although errors at this stage are very rare, they can lead to potentially very serious complications.

Advantages of Neuromodulation

  • It avoids the side effects caused by systemic drugs, such as excessive sedation, mental dullness, among others.
  1. No adverse systemic effects have been reported in the use of electricity.
  2. In the case of intrathecal administration of drugs, doses at least 100 times lower than those used orally are used.
  • Unlike spinal surgery, surgical decompression or ablative techniques (techniques used to injure structures), neuromodulation therapies can be tested prior to application. Usually, prior to the definitive implant, a test phase is performed where the patient can report if he/she finds relief with the therapy. This test phase can be performed without the need for surgical incisions.
  • Neuromodulation is a therapy that has been used for years and approved by the US Food and Drug Administration (FDA), the European Medicines Agency (EMA) for the treatment of pathologies such as persistent pain after surgery, complex regional pain syndrome, Parkinson’s disease or spasticity, and is also endorsed by the most reputable clinical guidelines (NICE, EFNS, KCE, ACC, NIMH, among others).
  • The devices can be removed if the patient wants to stop the treatment, it is a fully reversible therapy.

Other aspects to take into account:

  • As with many medical procedures, complications during and after neuromodulation therapy implantation can occur, but serious complications are rare in properly trained medical personnel.
  • There are several types of neurostimulators, and health professionals will choose the most appropriate one for each case.
  • Psychological assessment is usually performed prior to implantation of these therapies, as certain psychological problems may be associated with poorer outcomes.
  • Adjustment of electrical parameters is often necessary during the course of treatment.
  • Once the generator battery is depleted, it is replaced by a new battery with minimal surgical intervention.
  • There is the possibility of surgical revision of the neurostimulation system due to electrode displacement or breakage.
  • Stimulation modalities are divided into those in which the patient feels a slight tingling in the area of pain (paresthesia) and those in which the patient does not feel any tingling (paresthesia-free).
  • The patient is usually provided with a programmer so that the stimulation can be adjusted.
  • Rechargeable batteries are charged through the patient’s skin.
  • Most non-rechargeable batteries have a shorter half-life than rechargeable batteries (4-7 years vs. approximately 10 years).
  • The effectiveness of the stimulation may decrease over the years (tolerance), this is currently one of the fields of study where more research is being done to obtain solutions in this regard.
  • In certain diseases it has been described that the earlier the stimulator is placed, the better the results.