Neuromodulation or Neurostimulation is a promising modality for treating neurological disease (Parkinson’s disease, Tremors, Chronic Pain, seizures) as well as psychiatric disorders (Major Depression, OCD). The basic premise of neuromodulation is that by stimulating deep brain structures, it is possible to disrupt abnormal patterns of brain activity (in people with neurologic disease) and thereby restore normal brain electrical rhythms resulting in improvement and even resolution of symptoms. While the exact mechanism of how Neuromodulation works is not completely understood, it is believed that restoring normal brain electrical activity is essential to improve disease symptoms. Contrary to what many in the general public would think, a typical neurostimulating system is relatively simple in that it consists of only three components: an implantable stimulator generator/pulse generator (IPG), a lead, and extension wiring. Traditional Neuromodulation consists of continuous high-frequency stimulation (known as an open-loop system). While effective in minimizing some symptoms, this method of neuromodulation comes with the drawbacks of causing potential tissue damage from the constant stimulation as well as shortening generator (IPG) battery life to 2-5 years.
In continuous pursuit of a cure, neuromodulation companies/labs are developing increasingly sophisticated brain stimulators. Building off the success of the open-loop system, researchers have developed next generation systems that make stimulation more targeted not only in terms of where, but when stimulation occurs. This new targeted type of therapy where stimulation occurs in response to specific changes in a patient’s electrical brain activity is known as closed-loop neuromodulation. These implantable devices are able to record the electrical activities of many neurons continuously and as a result, determine patterns in the overall neural activity. The specific neural patterns are then able to be utilized as an input signal to the processor in the device that can sync neurostimulation with a specific event.
Consider that an early usage for neuromodulation was treating refractory epilepsy, an event that occurs spontaneously and unpredictably (much like that of a life-threatening cardiac arrhythmia). One could see the similarities between a neuromodulator and Automated Implantable Cardioverter Defibrillator (AICD), and thus the benefits provided by a closed-loop system. Much like how an AICD delivers a shock to stop an abnormal heart rhythm only when it occurs, an implantable closed loop neurostimulator can halt an epileptic seizure by delivering stimulation when it senses the beginning of seizure activity in the brain. While only an analogy, it makes sense that a device that only as beneficial in specific situations would be better to be triggered for that purpose alone.
The transformational benefit of closed loop neuromodulation clearly is a targeted therapy specific to an individual’s electrical brain activity, but other benefits of a closed loop system are still impressive such as a potential decrease in tissue damage as well as an overall decrease in power consumption leading to increased battery life (and subsequently avoiding frequent surgical IPG replacement). The benefits of the closed loop system are now starting to be quantified with early studies are demonstrating promising results with the treatment of epilepsy. A 2018 FDA approved study demonstrated that patients with a closed loop system experienced a 70% median seizure reduction after five years of therapy. This finding as well as numerous other promising ones are validating the benefits of a closed loop system. As a result of its individualization, closed loop neuromodulation can and is now being applied to all types of neuropathology. As the technology continues to be refined the benefits to those suffering will only increase.