Electrode Problems Create Neurotech Opportunity
by James Cavuoto, editor and Warren Grill, senior technical editor
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 Parkinsons 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, Lozanos 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 Parkinsons 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
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 Medtronics 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
years 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.