Functional Electrical Stimulation Field Converges in Cleveland

by James Cavuoto, editor

The spirit of a new industry and the promise of groundbreaking medical technology was in the air in Cleveland at the sixth annual conference of the International Functional Electrical Stimulation Society meeting in June. The five-day event, themed “Envisioning a New Century of Breakthroughs,” highlighted six "millennium" papers on key areas of neurotechnology, a truly international assembly of presenters, a small but solid core of neurotech manufacturers and sponsors, and several unique attributes not often found at a scientific or engineering meeting. A ubiquitous spirit of interdisciplinary cooperation linked this assemblage of biomedical engineers, neuroscientists, clinicians, therapists, and funding agencies. Several vividly interactive sessions featured frank, if at times cutting, discussion of research and product directions. A team of spinal cord injury patients was on hand—not just as poster children—but as active participants offering feedback and product suggestions to the engineers in attendance.

A panel of Spinal cord injury patients offered attendees critical feedback on current devices and future directions.

In a gripping keynote address, neurosurgeon and deep-brain stimulation pioneer Andres Lozano from the University of Toronto presented an overview of the use of DBS systems for treating neurological disorders such as Parkinsons, stroke, and tremors. Lozano related some impressive results treating serious cases with implanted electrodes in subcortical nuclei in the brain. He expects that neurodegenerative disorders will overtake cancer as the number two killer by 2040, when approximately one-third of the population will be affected. Looking beyond medical therapeutics, Lozano sees a coming merging of mind and machine as computational power increases and device miniaturization continues to create systems that rival the brain's connective population of 10^15 synapses and 1 millisecond time scale. He mentioned the possibility of someone acquiring preformed neural circuits that would endow the recipient with vital knowledge bases or motor skills. He also believes brain stimulation may have far-reaching applications treating obesity, depression, and other conditions.

Regeneration
One of the most productive sessions at the conference was a workshop devoted to neural repair and functional restoration. It highlighted several strategies for combining stimulation with neurobiological means of regenerating and repairing neural tissue. Researchers have found that an electric field oriented in the direction of a damaged neural fiber can enhance axonal regrowth. Panelists also discussed efforts underway to build hybrid neural/silicon devices that can be implanted in the nervous system to improve communication between artificial devices and neural centers. Entirely new or rebuilt pathways can be constructed in the nervous system by using stimulation to direct neurons and neurites to migrate and connect in the desired locations.

In another example of interdisciplinary cooperation, IFESS, composed largely of biomedical engineers, aligned with an association of surgeons and clinicians to coproduce a new journal called Neuromodulation.

Control and Engineering
Several sessions at the conference looked at progress in improving first-generation neural prostheses for hand grasp, bladder control, and standing/walking systems. Attendees argued for more natural human interfaces in the devices. For example, instead of the shoulder-actuated control currently used in many hand-grasp prostheses, a system controlled using electromyographic signals from the arm muscles, or a sensor that is based on the user's wrist angle, is felt to be more natural. In the bladder control stimulator market, current products such as NeuroControl's VoCare system work only by performing a surgical procedure known as rhizotomy, which deprives male patients of sexual function. New products that no longer require the rhizotomy are under development at a number of research institutions.

This surgically implanted wrist-angle sensor developed at the Cleveland FES Center offers a more natural user interface to a hand-grasp prosthesis.

Development of lower-extremity neural prostheses for standing and walking was the subject of pointed discussion during many sessions. Control engineers trying to perfect closed-loop feedback electronics that enable paralyzed patients to walk clamored for better sensors that offer precise information on biomechanical properties such as limb position and muscle force. Some neural engineers dismissed the overdependence on control theory as "mental masturbation." One participant, Gerald Loeb from the University of Southern California, claimed that efforts to build a walking prosthesis over the last 20 years have been misguided and the resources could have been directed to more achievable problems. Nonetheless, progress to date on standing and walking prostheses has many paraplegic patients and clinicians understandably excited, and the problems that remain appear to engineering issues and not limitations of basic science.

Consensus
Participants agreed that progress in smaller and smarter microelectrodes, including electrodes with multiple contact points and electrodes coated with neurophilic substances that promote electrode/neuron interaction, will be a key factor in the development of future products. There was also general agreement that the timing and sequence of patterned muscular activity after a spinal cord injury, stroke, or other neurological incident is critical to the patient's prospects for regaining function. Passive muscle stimulation and exercise patterns of simulated walking in paralyzed patients not only help counteract muscle atrophy and pressure sores, they also increase the probability that the patient will regain either natural or artificial use of the lost muscle function. Rahman Davoodi from USC showed a rowing machine for paraplegics that uses electrical stimulation to direct the sequenced activity of leg motions. This type of product appears to have considerable commercial potential for rehabilitation centers and even in-home use.

Government representatives on hand included Michael Weinrich, director of the NIH's National Center for Medical Rehabilitation Research, William Heetderks, of the National Institute of Neurological Disorders and Stroke, and Laura Bowman of the Department of Veterans Affairs. The two NIH organizations are the largest U.S. government funders of neural engineering programs, about $50 million per year--an amount that seem paltry given the promise of this technology. Weinrich said that the newly established National Institute of Biomedical Imaging and Bioengineering would have a budget of about $40 million in new funds, not counting funds diverted from existing institutes. Researchers in this field are nervously watching developments at the new institute. Some are optimistic that neural engineering can get a foothold in the new funding source; others are worried that key researchers and existing funds will be diverted from NINDS and NCMRR or that medical imaging will dominate at NIBIB.

Vendors
Exhibitors and sponsors at the event included several of the early manufacturers of neurotechnology products and systems. NeuroControl Corp. showed its FreeHand hand grasp proesthesis, the VoCare bladder stimulation system, and a new miniaturized multi-channel programmable stimulator call StIM. The device is targeted at stroke patients suffering from shoulder pain caused by the separation of the shoulder joint and weak muscles after stroke.

Medtronic, probably the largest corporation in the business—even though its neurotechnology product line is dwarfed by its cardiac products—promoted its InterStim urinary control system and DBS product line.

Cleveland Medical Devices showed its BioRadio 110, a compact and wireless brain monitoring device. Besides EEG signals, the product can transmit sensed ECG, EMG, EOG, and PSG signals to a nearby PC-based monitor. EIC Laboratories in Massachusetts exhibited its range of electrode coating products and services, which work with gold, platinum, silicon, iridium, and other materials. Empi showed its line of stimulators for pain treatment and neuromuscular rehabilitation. NeuroStream Technologies, a Canadian manufacurer, showed its line of implantable NeuroCuff interfaces, which accommodate electrodes as well as catheters for fluid infusion. Neopraxis Pty Ltd., an Australian firm, promoted its 22-channel Praxis stimulator, targeted at paraplegic patients. Advanced Bionics, one of the leaders of the cochlear implant business, promoted its line of BION leadless stimulators. The compact devices, measuring 16 mm long by 2 mm in diameter, can be inserted in a patient with a 12-gauge needle and controlled by a wearable RF transmitter.

In an intriguing prelude to the conference, nearby Case Western Reserve University, home of many of the pioneers of functional electrical stimulation, sponsored an Applied Neural Control Research Day, which updated attendees on developments in neuromuscular stimulation, electrode design, and other emerging technologies. The Cleveland FES Center, which organized the conference, had a large contingent of researchers, presenters, and technicians on hand. The non-profit organization is funded by the VA, CWRU, and MetroHealth Medical Center, and helps design neural prostheses which are later spun off to private industry.

Southern California was also well represented at the event. Besides the team from Advanced Bionics, the newly established Alfred E. Mann Foundation, as well as related teams from USC, the Alfred Mann Institute, and visual prosthesis company Second Sight llc were on hand.