Author: Robert Gross
Opportunities abound for stereotactic and functional neurosurgery in our mission to provide cutting edge care for patients suffering from disorders of the nervous system. The rapid pace of technological advancements is improving the care of patients typically within our purview, as well as opening up new vistas. This was in great display at the biennial meeting of the American Society for Stereotactic and Functional Neurosurgery in Denver in early June. A record 597 people-including 363 medical registrants (surgeons, neurologists, psychiatrists, scientists, engineers, and others) and 234 exhibitors from 18 countries assembled to present and discuss all the exciting advances in this vibrant and growing field.
Critical factors contributing to this growth are the NIH BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative (originated in 2013; amounted to $270M in grant funding in 2017 alone), as well as several programs of the Defense Advanced Research Projects Agency (DARPA). These programs were reviewed in the opening plenary session, with presentations from each of the agencies (NINDS, NIMH, DARPA), as well as 5 functional neurosurgeon-scientists currently undertaking supported preclinical and clinical research spanning movement disorders, epilepsy, language, memory and neuropsychiatric disorders. The remarkable catalytic effects of this support were shown by a quick headcount at a recent BRAIN investigator meeting, where no less than 11 supported functional neurosurgeons were in attendance, few of whom were supported by traditional NIH mechanisms. The BRAIN mechanisms are so-called 'cooperative' grants, which means that the program officers and NIH staff have a large oversight role in the funded research, not unlike the DARPA grants. While this requires a degree of back-and-forth between researchers and NIH staff, it also imposes risk to the researchers in that the funding is granted from year-to-year, whereas by traditional grants money is granted in 5-year blocks. The cooperative approach derisks the NIH for high risk/high reward projects-as almost all clinical research projects are-and allows for a broader range of projects, such as those in functional neurosurgery, to be funded.
Not only are technological innovations propelling functional neurosurgery, but the opening of new vistas is driving a potential for remarkable growth in our field as we bring new treatments to cohorts of patients previously not helped by neurosurgery-nor unfortunately, by traditional medical approaches. A plenary session at the biennial meeting explored some of these new areas. These include vision disorders, which actually have been a target for neurosurgery for decades (e.g. Richard Normann's lifetime of work at the University of Utah, where he invented the Utah Electrode Array specifically as a visual prosthesis; it subsequently became the basis for the Braingate system used as a motor prosthesis). That dream is closer to becoming a reality with the leveraging of the SecondSight (Symar, CA) thin-film micro-fabricated multielectrode array technology, FDA-approved as a retinal implant, as a cortical prosthesis. Also in the crosshairs are so-called peripheral disorders, such as 'neurocardiology' and 'neuroimmunology' (e.g. Crohn's disease). The latter are being driven forward by another NIH initiative, Stimulating Peripheral Activity to Relieve Conditions (SPARC). This initiative has the potential to bring relief to millions of patients, and to bring millions of patients to the functional neurosurgeon's operating room.
In addition to funding risky clinical programs that utilize technological innovations, the BRAIN and DARPA programs are propelling remarkable advances in those technologies themselves. In fact, the espoused goal of the DARPA Neural Engineering System Design (NESD) program is to record from 106 and stimulate 105 electrodes, according to program manager Dr. Alfred Emondi. A session highlighting engineering advances included new ultra-thin, hi-density arrays and new microchips that can record from large arrays and provide computational support for handling the data. These go hand in hand; Moore's law is as applicable to neural interfaces as it is to the data sciences. The inexorable increase of processing power and decrease of power consumption is allowing the necessary frontloading of computational burden to the implantable devices, and undoubtedly will be an underpinning to the revolution of neurosurgery. As these powerhouses advance to clinical application in the coming years, we will see applications to disorders, such as memory, that were previously untouchable.
More esoteric and controversial is the use of neurotechnology to 'extend cognition', amongst the goals of Kernel. Founder Bryan Johnson gave a provocative interview with past-president Aviva Abosch about the interface of artificial and human intelligence. This was bookended by a highly attended plenary on neuroethics, an area of study that is, by necessity, evolving nearly as quickly as our new technologies. The pace of innovation is becoming so rapid that an emerging threat accompanies it. With the possibility of extending ourselves too far in our efforts to alleviate suffering, bridging the oft-times nebulous boundary between treating dysfunction and improving function is brought to the fore in conditions that affect memory and mood.
Another threat that was addressed at the Denver meeting was cost effectiveness and outcomes. DBS (and all these new technologies) is expensive and, with the increasing numbers of indications being explored, has the potential to go from a rounding error in the CMS budget to an albatross to the healthcare system. We must increasingly consider and document all the downstream expenses that are alleviated and the increased productivity and unquantifiable benefits of improved quality of life that are associated with effective treatments. We must also be responsible stewards by taking a hard look at expensive technologies that, although FDA and CMS approved, may not deliver a sufficient 'bang for the buck'. Working together with all stakeholders, functional neurosurgery needs to continue to strive to move our treatments from 'good to great'.
Several major themes have increasingly been percolating through virtually all streams of functional neurosurgery. The first is closed-loop feedback controlled neuromodulation, which includes (1) recording of neural signals, aka 'sensing'; (2) computational analysis of the signals, including the application of machine learning techniques to classify the data for subsequent action; (3) actuation, which includes any means of effecting change upon the nervous system (including electrical stimulation, but also other techniques such as optogenetics); and (4) closing the loop by recording the effects, and using control algorithms to monitor and revise actuation on the basis of its effects.
Phil Starr, the honored guest of the ASSFN meeting and a BRAIN and DARPA supported investigator, gave several presentations covering his team's (and other's) remarkable progress in developing closed loop technology for autonomous control of DBS for Parkinson's disease. Other presentations concerned closed loop control in epilepsy, addiction, depression, tremor and neuroprosthetic control. The second, interrelated theme is the use of both structural (e.g. diffusion tractography) and functional (e.g. resting state oscillations) connectivity to characterize the networks involved in both normal and pathophysiological states. This also cuts across most of the areas of functional neurosurgery, since circuits underlie all normal function. Like closed loop control, network analysis also is facilitated by the remarkable advances in computational analysis and data storage. Finally, data science per se is the third theme. This spans from advancements in ways to handle the incredible quantity of information coming from large channel count (106!) arrays recording at 20 or 30kHz, to the probabilistic analysis of the DBS implanting behavior of surgeons in thousands of cases to identify best targets, to the truly 'big' data from capturing the social media behavior of patients with/without depression. The ability to do big data science is again driven by technological advances in computer hardware and software.
The threads of a remarkable era of neurotechnology innovation, computer innovation, a robust funding environment, and a relatively less risk-averse venture milieu than in the past decade are coming together to propel the area of stereotactic and functional neurosurgery to the forefront of the field of neurosurgery, after arguably being a backwater for most of the 20th century. Increasing demand, with the aging of the populace as well as anticipated increases in the incidence of disorders such as Alzheimer's and Parkinson's disease, will continue to make stereotactic and functional neurosurgery a hotbed for at least the remainder of the 21st century.