Other firms offer alternative approaches to DBS for treatment of neural disorders. For example, Houston-based Cyberonics owns broad patents giving the company a near monopoly on neurostimulation for epilepsy. Called VNS (vagus nerve stimulation), the therapy features an IPG, roughly the size of a small pocket watch. Implanted in the patient's left chest area, the device stimulates the left vagus nerve in the neck with a helical-shaped, platinum iridium electrode that wraps around the nerve.

“The advantage of stimulating the Vagus Nerve, which serves as the superhighway to the brain, is that it is easy to access and there is no penetration of neural tissues,” says engineer Reese Terry, the company's interim CEO. “It is also a relatively easy system to implant and program.” Some 45,000 epilepsy patients have already received VNS therapy and the company is targeting the technology for other conditions, such as severe Depression.

Meanwhile, a fledgling competitor, California-based NeuroPace, is sponsoring an investigational device study of its Responsive Neurostimulator (RNS) System. Implanted in the skull, the RNS is designed to detect abnormal electrical activity in the brain and then deliver electrical stimulation that normalizes brain activity before the patient experiences seizures.

In Seattle, Northstar Neuroscience is also developing an alternative to deep brain surgery for patients recovering from stroke. The company has designed a family of electrodes aimed at stimulating various sectors of the cortex — the outer layer of the brain — that control movement, emotions, hearing, speech and other functions. This year, in its first application, the company hopes to complete pivotal clinical trials for stimulation therapy aimed at improving hand and arm movement in patients recovering from stroke.

In this particular treatment mode, the surgeon will place an array of six electrodes, about the size of a postage stamp, on top of the dura, which is the membrane that covers the brain's service. This cortical stimulation lead connects to an implantable pulse generator in the chest.

“We saw a number of advantages in focusing on the cortex,” says Northstar COO Jeff Bowers. “First of all, it controls many neurological functions and therefore is a fertile target for intervention. And, as the outer layer of the brain, the cortex is easier for surgeons to access than deeper brain structures.”

Bowers, whose goal is to commercialize the therapy for hand and arm movement by the end of 2008, adds, so far there is no FDA-approved implanted neurostimulator for stroke recovery. But the potential market is great. Some 5 million Americans are stroke survivors, with more than 500,000 new stroke victims surviving each year.

Such examples are just a sampling of the fast-expanding neurotech applications now being developed. Name a malady and there is likely to be a device aimed at treatment.

In Cleveland, NDI Medical has developed what it describes as the market's smallest multi-channel wireless rechargeable IPG. About the size of a thumb and implanted in the lower abdomen, the device is now being tested in clinical trials as a “bladder pacemaker” to control urinary Incontinence. To achieve its miniaturization goals, NDI turned to Valtronic, a contract manufacturer specializing in microelectronic modules. Valtronic used a circuit assembly technology called 3D chip-scale packaging (3D-CSP). With this process, several flip-chip circuits are assembled on flexible circuit boards, then folded into a compact package. The result: a package 75 percent smaller than conventional assemblies.

“It's a very exciting time for the neurotechnology industry,” says NDI Medical president Geoffrey Thrope, a biomedical engineer who also was co-inventor of FREEHAND™, an FDA-approved stimulation device to restore hand control to individuals with spinal cord injury. Ten years from now, predicts Thrope, the market for neurotechnology devices could be as high as $20 billion.

Among the applications that could substantially boost that dollar volume are devices for controlling obesity. In the U.S. alone, nearly 15 million people are considered morbidly obese. For such patients, neurostimulation could offer a better and safer alternative to gastric bypass surgery, a procedure with a high risk of mortality and an often lengthy recovery.

EnteroMedics, a privately held Minnesota company with research ties to the Mayo Clinic, has developed a therapy called VBLOC. In this system, a surgeon uses a laparoscope to insert two tiny electrodes next to the vagal nerves just above the junction between the esophagus and the stomach. An implanted neuroregulator, linked to the electrodes, produces low-energy, high-frequency electrical impulses to block the vagal nerve signals responsible for such functions as expansion of the stomach as food enters.

The company is already conducting clinical trials of VBLOC at several sites around the world and is seeking an Investigational Device Exemption from the FDA in advance of planned clinical trials in the U.S. this year, according to CEO Mark Knudson.