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What is the Brain-Machine Interface
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Deep brain stimulation is rapidly emerging as one of the most promising applications of neurotechnology. Over the last few years, the procedure, which involves surgical implantation of one or more electrodes in the thalamus or basal ganglia brain regions beneath the cerebral cortex, has proven to be an effective treatment for the movement disorders that occur in Parkinson's Disease or essential tremor.
But complications with DBS electrodes reported recently in the scientific literature have raised some issues that must be addressed before this industry segment can achieve complete commercial success. In the June 2002 issue of the medical journal Neurosurgery, Andres Lozano and colleagues from the University of Toronto report that about one-fourth of the patients implanted with DBS electrodes have experienced hardware complications such as migration or dislodgement of the leads. The authors tracked specific problems with the electrodes and connectors, which included lead fractures, lead migrations, short/open circuits, erosions, infections, and foreign body reactions.
Lozano has been a strong proponent of DBS treatment in the past. He was the keynote speaker at the 2001 meeting of the International Functional Electrical Stimulation Society meeting in Cleveland, where he reported that up to 70 percent of his Parkinsonian patients experienced notable improvement resulting from the procedure. As such, Lozano's critical analysis of DBS hardware is likely to receive a good deal of credibility. In the paper, he contends that hardware-related complications may be more troubling for neurosurgeons than stimulation-related side effects. Although recent relocation of the connector from the neck to the head appears to reduce the frequency of lead-related complications, it is clear that DBS could benefit from further development of the hardware and surgical technique.
Aside from hardware reliability issues, DBS pioneers are grappling with more basic issues such as the optimal electrode location. The mechanisms by which high-frequency electrical stimulation of deep brain structures improves motor function is an area of intense research and debate. A recent study by Voges and colleagues published in the Journal of Neurosurgery further complicates the issue.
The authors combined pre- and post-operative images to correlate electrode position and outcome for subthalamic nucleus (STN) stimulation in persons with Parkinson's disease. The results suggest that electrodes placed well outside of the anatomical target, STN, may still result in excellent outcomes, thus challenging this well-accepted surgical target.
Currently, the only FDA-approved manufacturer of DBS systems is Medtronic, which makes both a single-channel device and a newly approved dual channel stimulator called Activa. Their current technical problems may create opportunities for potential competitors such as Advanced Neuromodulation Systems, of Plano, TX, and NeuroPace, of Sunnyvale, CA, which is initially targeting epilepsy applications.
The Lozano study may also give a boost to component manufacturers such as microHelix, Inc., of Portland, OR, who manufactures implantable cable assemblies for neurostimulators. microHelix is believed to be developing hardware for a future version of Medtronic's DBS system. Other manufacturers of implantable cables and connectors include Foster-Miller, Inc., and Innersea Technologies, of Lexington, MA, which is working on insulating materials for implanted electrodes.
The Voges study illustrates the importance of neuroimaging in implanting and evaluating neurotechnology interventions. A number of firms manufacture stereotaxic neurosurgical tools and imaging systems that play an important role in the DBS implantation procedure. Also, manufacturers of magnetoencephalography systems such as 4-D Neuroimaging in San Diego and VSM Medtech in Vancouver may benefit if they can position their systems as tools for functional brain mapping prior to DBS electrode implantation. Any tools that simplify the implantation process will help sell new systems. At last year's NIH Neural Prosthesis Workshop, a DBS recipient on the user panel listed this at the top of her wish list.
Several other neurotechnology system and component manufacturers stand to benefit as more is learned about the mechanisms by which deep brain stimulation works, As this happens, and as manufacturers address the hardware reliability issues, the market opportunity for DBS may well expand beyond movement disorders to a host of other neurological and psychiatric diseases and disorders.
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