Editing Deep brain stimulation (section)

==Future developments==
In early 2025, Medtronic achieved the [[CE marking|CE mark]] as the first clinically available closed loop system in the world, and the technology is now being used in the [[European Union]] and the [[United Kingdom]], though it has yet to receive FDA or Medicare approval in the United States.<ref>{{cite news |title=Medtronic achieves CE Mark approval for BrainSense™ Adaptive deep brain stimulation and Electrode Identifier, a groundbreaking advance in personalized, sensing-enabled care for people with Parkinson's through innovative brain-computer interface technology |url=https://news.medtronic.com/2025-01-13-Medtronic-achieves-CE-Mark-approval-for-BrainSense-TM-Adaptive-deep-brain-stimulation-and-Electrode-Identifier,-a-groundbreaking-advance-in-personalized,-sensing-enabled-care-for-people-with-Parkinsons-through-innovative-brain-computer-interfac |access-date=8 February 2025 |work=Medtronic News |language=en}}</ref> Closed feedback loop systems deliver a lower total charge to the brain over time because their trigger for neurostimulation is based on a threshold signal from the individual themselves, rather than being assigned through external programming of the device by a clinician.<ref name = "Handbook Clinical Neurology 2022"/> Studies have shown lower total electrical energy delivered with adaptive DBS and a 40% reduction in motor symptoms, though research thus far comparing adaptive and conventional DBS has suffered from publication bias.<ref name = "Journal of neurology 2023">{{cite journal |last1=An |first1=Q |last2=Yin |first2=Z |title=Adaptive deep brain stimulation for Parkinson's disease: looking back at the past decade on motor outcomes. |journal=Journal of Neurology |date=March 2023 |volume=270 |issue=3 |pages=1371–1387 |doi=10.1007/s00415-022-11495-z |pmid=36471098}}</ref>

In both open and closed loop systems, there are a basic set of neurostimulator parameters can be modified such as choice of contact configuration (monopolar, [[bipolar neuron|bipolar]], double monopolar, double bipolar), stimulation [[amplitude]], [[pulse width]], and [[frequency]]. Segmented leads were introduced in 2015, allowing the possibility of steering and orienting the stimulation horizontally. This led to both an increased specifity of treatment zone and an increase in time needed for device programming. Symptom specific and task-dependent neurostimulation, similar to rate adaptive [[cardiac pacemaker]]s, is under development but not yet clinically available.<ref name = "Handbook Clinical Neurology 2022"/>

Though a wide variety of sources have been studied as feedback loops to trigger neurostimulation, the two that have been clinically tested are electricocortical and kinetic. Electricocortical signals in the brain can be recorded by an unused DBS electrode contact via [[electrocorticography]]. [[kinetic energy|Kinetic]] signals are triggered by [[wearable technology]] that detects [[tremor]], usually a [[gyroscope]] or [[accelerometer]].<ref name = "JAMA neurology 2013"/>  Most electrocortically based feedback devices thus far have used [[beta wave|beta activity]] as the primary feedback signal, though this does not always correlate with symptomatology. A minority have used wearable devices.<ref name = "Journal of neurology 2023"/> Besides tremor, wearables can be used to track other motor symptoms like bradykinesia, levodopa induced dyskinesia, freezing of gait, [[festination]], and balance impairment.<ref name = "Handbook Clinical Neurology 2022"/>  Wireless nanoparticals,<ref>{{cite journal |last1=Wu |first1=J |last2=Cui |first2=X |last3=Bao |first3=L |last4=Liu |first4=G |last5=Wang |first5=X |last6=Chen |first6=C |title=A nanoparticle-based wireless deep brain stimulation system that reverses Parkinson's disease. |journal=Science Advances |date=17 January 2025 |volume=11 |issue=3 |pages=eado4927 |doi=10.1126/sciadv.ado4927 |pmid=39813330|pmc=11734722 |bibcode=2025SciA...11O4927W }}</ref> neurochemical ionic changes, local neurotransmitter level, electrode-electrolyte interfaces, and impedance spectroscopy, amongst others, are currently being researched for adaptive systems.<ref name = "Handbook Clinical Neurology 2022"/>

Microelectrodes can be used for local neuronal firing patterns while macroelectrodes can be used to detect local field potentials, whose detection correlates with time locked bursts of neuronal spikes from synchronous neural oscillations.<ref name = "Handbook Clinical Neurology 2022"/>

A challenge of closed loop DBS is the obscuration of brain activity from artifact of the neurostimulation itself. By recording and stimulating in the same area, DBS devices capture the impulses of the delivered electric stimulation. While theoretically useful as a feedback signal, this artifact must be carefully filtered to prevent saturation of the sensing amplifiers and introduction of fictitious resonant information. This issue has been partially mitigated by advancements in wire insulation, but it still persists. An alternative input signal for aDBS that has been suggested is the evoked resonant neural activity, as it has a better signal to noise ratio than beta oscillations.<ref name = "Handbook Clinical Neurology 2022"/>

New DBS systems are being developed with current steering that allows the application of current in a focal as opposed to a concentric ring around the activated contact. Future DBS electrodes also will have more than four contacts, allowing for finer control of the stimulation area. Segmented contacts have also been developed with each piece having the potential for its own individual stimulation. The manufacturer St Jude is already approved for this for this in Europe and it has FDA approval in the United States. Blinded intraoperative use of directional current with segmented electrodes has been found to have a higher therapeutic window (>41.3%) for STN PD and VIM in essential tremor, as compared to standard omnidirectional stimulation. Boston Scientific has developed leads with eight contacts, each with an independent current source, allowing separate manipulation of DBS parameters (amplitude, frequency, pulse width, and current) at each contact; these have already been approved for use in Europe. Directional current capabilities of the new technology could be more beneficial than simple monopolar settings because they may allow shielding of brain regions with current shaping and steering may be useful to lower the side effects. Potential negatives increased programming time with further programming alternatives, the degree of the programmer's accuracy in "steering" the electrical current to the needed areas and that the decreased surface area due to smaller contacts will increase impedances and increase battery drainage. In essential tremor that is poorly responsive to initial DBS, another set of electrodes was placed in close proximity so that current could be directed from one electrode to the other, has been used as "rescue" therapy for ET; two-electrode system provides greater volume of tissue activation, but more static damage due to second electrode.<ref name="Vanderbilt 2017"/>

Optogenetics is a new technique that may allow activation of neurons using light rather than electricity.<ref name = "JAMA neurology 2013"/>