The Various Types of Neurostimulators

By 

Dr Nicholas Hool

Published 

August 10, 2022

Neurostimulation is a method of applying energy to the central or peripheral nervous system for the purpose of causing a neurophysiological response intended to treat or improve symptoms for various medical conditions. It is particularly useful because it is passive treatment that directly interacts with the body’s nervous system, which is more precise and has less side effects than medications and is powerful when paired with common drug-free techniques like cognitive behavioral therapy, EMDR therapy, or mindfulness and meditation practices. It is a technology that has a wide range of applications and holds promise to help people break free from dependence on medications and improve quality of life. 

Neurostimulation holds the promise to be powerful as a core mental health treatment leading to long lasting positive effects, and it can also be a powerful tool to help patients with symptom control for several years after the core treatment for their condition is complete. The question is, which neurostimulation methods fall into which treatment categories, and which ones are most effective? Many neurostimulation methods are not practical for daily use and long-term symptom control, and other devices are not powerful enough to cause changes in the brain that lead to long-lasting positive effects. This article intends to help shed light on which types of neurostimulation methods fall into each category. 

The Neurostimulation Spectrum

There is a large spectrum of neurostimulation devices and methods that have been well researched and developed. There are invasive, percutaneous (minimally invasive), and even noninvasive forms of neurostimulation. This article presents a short review of the various types of noninvasive neurostimulators and includes an overview of their principals of operation, mechanism of action, indications for use, cost, and usability. This article does not take into account every type of noninvasive neurostimulation method, but only those supported by large amounts of independent research with demonstrated efficacy through rigorous scientific studies. 

*If you are considering a neurostimulation technology to try as a core treatment or as a tool for long-term symptom control, but you are unsure if a new technology you’ve come across is actually effective, use PubMed to search for independent studies and reviews of that technology for the application you are considering! If a technology has limited information on PubMed, you may want to start with a more scientifically-proven technology.*

Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is a method that involves applying electromagnetic impulses to the brain using coils placed on top of the skull over the target brain region. These brain coils produce magnetic waves that are sent into the brain, where neurons pick up those magnetic waves and translate them into electrical signals, which leads to an action potential and activation of the functional neural circuit of interest. Repetitive use can induce long-term changes to brain circuits and networks, which is a powerful treatment technique for patients with dysfunctional neural circuitry. TMS is currently FDA-cleared to treat Major Depressive Disorder and Obsessive-Compulsive Disorder, and several studies have demonstrated the method is effective to treat patients with generalized anxiety disorder, post-traumatic stress disorder, panic disorder, and other anxiety disorders. 

TMS protocols for depression and OCD typically consist of treatment sessions that last between 5-20 minutes, and are administered once per day for 2-6 weeks straight, depending on the condition and severity of the condition. TMS devices are large machines that are only found in offices of certified TMS practitioners (psychiatrists) and therefore require a large time commitment and daily travel to a doctor’s office. Treatments are by prescription only, and a full treatment regimen can cost up to $15,000. While TMS is slowly gaining insurance coverage, it is rarely fully covered by insurance and still requires a large out-of-pocket expense from the patient. 

TMS is considered a core mental health treatment, intended to cause long-lasting effects. It is not designed nor practical to be used for daily symptom management over the long-term. 

Sources

Transcranial magnetic stimulation in anxiety and trauma‐related disorders: A systematic review and meta‐analysis (nih.gov)

Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS): An update (2014–2018) - ScienceDirect

Focused Ultrasonic Stimulation

Brain stimulation via focused ultrasonic stimulation is a method that sends a focused ultrasonic beam into the brain to stimulate a very precise region of the brain. The mechanism of action is not clear, but it is generally understood that the focused ultrasonic beam creates a small area of high pressure in the brain, and that high pressure results in mechanical stimulation of the target brain region, leading to action potentials and activation of the neural circuitry associated with the target region. 

Focused ultrasonic stimulation is a noninvasive procedure that involves placing an ultrasound transducer designed for ultrasonic stimulation on the skull over the brain region intended to be stimulated, but it is different than TMS in that it can stimulate regions of the brain with far greater precision, and can target deeper brain structures than TMS. It is a relatively newer method of noninvasive brain stimulation and is currently being tested for a large number of medical indications. The common consensus in the research community is that focused ultrasonic stimulation is capable of treating the same conditions as invasive deep brain stimulators because it can target precise regions in the brain of any depth. If that is the case, then focused ultrasonic stimulation could be a powerful noninvasive neurostimulation method that replaces high-risk and costly procedures of receiving a deep brain stimulation implant. 

Once focused ultrasonic stimulation becomes widely available, it will still require several office visits to receive treatment, similar to TMS. However, it will likely cost a significantly lower amount than a TMS protocol for the same indication. 

Focused ultrasonic stimulation would be considered a core mental health treatment, intended to be used for a short amount of time to cause long-lasting changes. It is not designed nor practical to be used as a method to manage daily symptoms over the long term. 

Sources

Safety of transcranial focused ultrasound stimulation: A systematic review of the state of knowledge from both human and animal studies - Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation (brainstimjrnl.com)

https://neurofus.com

Electroconvulsive Therapy

Electroconvulsive Therapy is a method that involves delivering a large dose of electricity across the skull and through the brain for a very short amount of time in order to treat various conditions such as depression and schizophrenia. The mechanism of action is not clearly understood, but it is believed to have therapeutic effects by causing a seizure in the brain for a short amount of time, which then resets the neural circuitry associated with the condition and therefore treats the underlying condition. It is commonly used as a last resort when medications do not work, and it is typically used for only a few sessions. It is a controversial method because there is data that suggests ECT leads to memory loss and other long-term side effects. 

ECT can only be administered by a psychiatrist or medical doctor, requires office-based treatments, and requires sedation using anesthesia before the procedure. It takes about an hour to prepare for the procedure and an hour to recover from the procedure. Common treatment protocols consist of 3 treatments per week for 2-3 weeks. The treatment is very expensive, costing up to $2,500 per treatment session. 

ECT is considered a core treatment intended to be used once and to cause long-lasting changes and improvements in mental health. It is typically used as a last resort and is not designed nor practical to be used for daily symptom control over the long term. 

Sources

How Electroconvulsive Therapy Works?: Understanding the Neurobiological Mechanisms (nih.gov)

Electroconvulsive Therapy - StatPearls - NCBI Bookshelf (nih.gov)

Transcutaneous Vagus Nerve Stimulation

Transcutaneous vagus nerve stimulation (tVNS) is a neurostimulation method that has become very popular in the last decade. tVNS operates using the same principal of operation as a TENS unit (transcutaneous electrical nerve stimulation). TENS units are devices that noninvasively apply electrical energy to a nerve near the skin to stimulate the nerve and cause a desired therapeutic response. The most common use case for TENS is to treat pain, and this type of device has a well understood mechanism of action, has very low adverse effects, and is FDA-cleared for a variety of indications. 

tVNS devices are basically TENS units that specifically stimulate the vagus nerve. The vagus nerve is the largest cranial nerve and has distribution throughout the head, neck, and torso. It is primarily responsible for modulating sympathetic and parasympathetic output, or stress and relaxation levels. There are many therapeutic benefits that come from stimulating the vagus nerve, and many more are being explored in research. 

You can noninvasively stimulate a branch of the vagus nerve over the neck and in and around the ear area. tVNS works by activating the neural circuit connected to the vagus nerve, which includes regions in the Locus Coeruleus and the Limbic System. These brain regions play a major role in controlling mental health states like anxiety and depression, and tVNS has repeatedly been shown to activate these brain regions and improve symptoms of anxiety and depression. 

tVNS devices are much smaller than core treatment devices like TMS, FUS, and ECT machines. They are devices that can fit in a person’s hand or on a desk in a home environment. tVNS protocols typically consist of daily treatments for 15-30 minutes per day for 3-4 weeks at a time, depending on the condition being treated. However, one tVNS device has demonstrated clinically significant reductions in anxiety levels after just a single 10-minute treatment in a clinical study, suggesting it could be a powerful symptom management tool for patients who frequently experience anxiety and anxiety attacks. 

While significantly more affordable than other core neurostimulation treatments, tVNS devices can still cost upwards of $3,000 and are not typically covered by insurance. They are being researched for use as a core treatment intended to have long-lasting effects, but the most practical use for tVNS is for long-term daily symptom management. tVNS is an excellent technology to pair with a core treatment protocol such as psychotherapy, medication treatment, and other neurostimulation treatments and can be safely used for the rest of one’s life. 

Sources

Optimization of Transcutaneous Vagus Nerve Stimulation Using Functional MRI (mvclinic.es)

Critical Review of Transcutaneous Vagus Nerve Stimulation: Challenges for Translation to Clinical Practice (nih.gov)

Cranial Electrotherapy Stimulation

Cranial electrotherapy stimulation (CES) is a noninvasive neurostimulation method that uses low-intensity and low frequency electrical stimulation waveforms applied to the head, earlobes, or neck area. The technology is technologically identical to TENS or tVNS but uses much lower output intensities. CES devices have been around since the 1960s and are FDA-cleared to treat anxiety, insomnia, depression, and pain. CES is intended to be used daily for 20-30 minutes for 3-4 weeks at a time before effects are realized. 

The mechanism of action of CES is not clear and most sources use vague language to describe how it works such as “CES stimulates serotonin in the brain to help induce a calming effect.” Serotonin cannot be stimulated. Serotonin can be produced as a result of neurostimulation, but only when a precise neural circuit is stimulated. Precision is the most important variable for effective neurostimulation, and CES generally has a negative perception in the research community because of its lack of precision. 

The most common CES technique used in research is to apply ear clip electrodes to a patient and apply stimulation bilaterally across the head. However, this treatment method is also used as a sham location in many tVNS studies because it is free from nerve innervation. Another common method is to apply wet sponge electrodes across the forehead and electrically stimulate the cranium. This is the oldest method of CES and does not precisely stimulate any particular nerve (with possible exception to trigeminal nerve stimulation), which is why some research casts doubt on the positive effects of this method.  

CES can have positive effects for patients with real mental conditions if used properly. It is believed that CES is effective when it is applied to the vagus nerve (tVNS via CES) because the vagus nerve and its neural circuitry is implicated in many mental health conditions. An ideal location for effective CES could be on the side of the neck just below the ear over a region called the tympanomastoid fissure. This region contains the auricular branch of the vagus nerve and the great auricular nerve. There are at least two CES devices available that apply treatment to this location, and these devices are FDA-cleared for anxiety relief when used daily for weeks at a time. 

CES devices can cost between $500 - $3000 and may or may not be covered by insurance, depending on the plan you have and the past treatments you have already tried. Properly configured and precise CES devices are ideal for patients who need effective long-term symptoms management techniques. They are an excellent supplement to core treatment methods such as psychotherapy, medication, and other neurostimulation treatments. 

Sources

A Critical Review of Cranial Electrotherapy Stimulation for Neuromodulation in Clinical and Non-clinical Samples (nih.gov)

Optimization of Transcutaneous Vagus Nerve Stimulation Using Functional MRI (mvclinic.es)

Other Neurostimulation Methods

There are many other types of neurostimulation methods being tested to treat various medical conditions such as transcranial direct current stimulation (tDCS), pulsed electromagnetic field therapy (pEMF), and red light photobiomodulation. There are also an uncountable number of wellness devices and products being sold that claim their technology is rooted in science and can do many things at once. For example, there are neurostimulator wellness devices that claim to improve focus, enhance performance, increase clarity, improve sleep, boost energy, manage stress, and provide many other wellness indications. Time will tell which devices and methods turn out to be the most effective for patients. 

It is an exciting time for neurotech companies and patients looking for effective drug-free alternatives, but when deciding to invest in a neurostimulation treatment or product, you should ask yourself what it is intended for (core treatment or long-term symptom management), if it has supporting independent research, and how well the device or treatment is designed to fit in with your lifestyle. 

Beware of companies that market their product as being capable of treating several indications all at the same time yet lack substantial support in independent literature. Remember, effective neurostimulation is dependent on the precision of the nerve or brain structure being targeted. A neurostimulation product that has several indications all at the same time likely means that device has low treatment precision and therefore low efficacy. 

Despite the prevalence of imprecise and less-than-substantiated neurostimulation products available, it is still worth noting that the placebo effect is real and often works for many patients. As Earl Bakken, co-founder of Medtronic, Inc. says, “If the objective is to obtain beneficial results for the patient, it doesn’t matter whether it’s a placebo or a device – use it!” (One Man’s Full Life, page 20. Bakken, 1999). As a result, you should strive to learn about as many neurostimulation devices as you can, so that you can make an informed decision about what device will best meet your needs.

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