Deep inside the brain, where Minneapolis neurologist Dr. Jerrold Vitek works, electricity can be wielded as a tool to treat problems from movement disorders like Parkinson's disease and essential tremor.
Until recently, permanently implanted deep-brain medical devices could only distribute power in a spherical area around the end of an electrode. But a symmetrical shape is not always ideal when Vitek wants to stimulate certain parts of the brain but avoid other areas just millimeters away.
Now Vitek is among the first doctors in Minnesota and around the country who are adopting a new device from Abbott Laboratories' St. Jude Medical catalog called the Infinity Deep Brain Stimulation System, which includes equipment that lets a surgeon "sculpt" the electric field inside the brain for precise stimulation.
"This is the first real advance in technology that we have seen in probably 20 years in the U.S.," said Vitek, who is head of the neurology department and director of neuromodulation research at the University of Minnesota. "Being able to sculpt this current field, we can make sure we are only in the areas that we want to be in."
Movement disorders like Parkinson's disease and essential tremor are caused by communication breakdowns in the nervous system that lead to loss of muscle control and cause involuntary movements.
Although it's still not fully understood why it works, deep-brain stimulation (DBS) has been used for decades to treat serious symptoms of movement disorders by sending electric current to specific structures in the brain, like the subthalamic nucleus.
The current is sent from a pacemaker-like generator implanted in the chest, which has an expected battery life that is measured in years, not decades. But the surgical innovation behind the Infinity DBS is at the far other end of the device — the tip of the electrode placed in the brain.
Traditional neuromodulation wires send out current from circular bands shaped like the metal band that holds an eraser to a pencil, but much smaller.
On the Infinity DBS lead, some of the bands are divided into discreet segments that can be turned on or off if the doctor decides one side of the lead is too close to a part of the brain that would trigger side effects like facial twitching or speech problems.
"That enables physicians to steer current toward the targeted structures in the brain and avoid unwanted side effects," said Subhan Khan, divisional vice president for research and development in Abbott's neuromodulation business.
(Neuromodulation was a division of Minnesota-based St. Jude Medical before Chicago's Abbott Labs acquired it in January. Abbott has said St. Jude's neuromodulation division was one of the key assets it sought to acquire in the deal.)
Khan said one of the biggest engineering challenges was figuring out how to fit the wiring for eight electrical contacts into a lead 1.27 millimeters wide. That was a design requirement because St. Jude decided its DBS system should be compatible with the tools used with traditional 1.27-mm neurostimulator leads.
"Brain surgery is complex enough. For us it was a paramount objective not to change the physicians' workflow," Khan said.
But for patients, Abbott wants to totally change how they interact with a DBS device.
Abbott says the Infinity is the only DBS system that can be adjusted through an app on a Bluetooth-enabled Apple iPod Touch. The controller functions and looks almost exactly like an iPhone, but without the phone itself.
John Alexander, a 65-year-old patient with Parkinson's in central Florida, says the difference his Infinity DBS makes is so profound that observers can tell within seconds when he uses his iPod controller to briefly turn it off.
"There is a dramatic difference in the level of control of my tremor when the device is turned on and working," said Alexander, who was diagnosed at age 58.
Alexander was the first U.S. patient to have an Infinity DBS implanted after the FDA approved the device last October. Since then he's been able to type again and eat soup with a spoon, and has cut his Parkinson's medications by half.
His iPod controller can be used to alternate among several stimulation settings programmed in by his medical team, and also adjust the strength of his continuous stimulation. But after half a year of use, he says he only occasionally needs to adjust the device anymore.
With the device on, "My handwriting has improved, the pain has lessened, and I am much more comfortable in social settings. … I feel it has rolled back my symptoms four or five years," he said.
