HILTON HEAD—A new implantable device for deep brain stimulation (DBS) may soon be available to neurologists, according to an overview provided at Vanderbilt University School of Medicine’s 38th Annual Contemporary Clinical Neurology Symposium. The FDA approved the Brio Neurostimulation System, which was developed by St. Jude Medical, in June for the treatment of essential tremor and Parkinson’s disease.
The system consists of an approximately 2-inch-by-2-inch electrical pulse generator for implantation under the skin of the upper chest and wire leads that attach to electrodes placed within the brain. Each lead has four contacts, and the distal contact is an active tip. The system’s battery is rechargeable, and the system is based on a constant current.
One trial supporting the Brio Neurostimulation System’s safety and effectiveness included 136 patients with Parkinson’s disease, and a second included 127 patients with essential tremor. All patients’ symptoms were inadequately controlled with drug therapy. Researchers implanted the Brio Neurostimulation System in all patients and assessed effectiveness at three months for patients with Parkinson’s disease and at six months for patients with essential tremor. Both groups had statistically significant improvement on their primary effectiveness end point when the device was turned on, compared with when it was turned off.
Fenna T. Phibbs, MD, MPH
Patients with Parkinson’s disease used the system in addition to medication, and the majority of patients with essential tremor who used the device were able to control their symptoms without the need for medications. Serious adverse events included intracranial bleeding, and other device-related adverse events included infection and dislocation of the device lead under the skin.
A potential difficulty of the Brio system is that insurance companies have been reluctant to cover systems with rechargeable batteries, said Fenna T. Phibbs, MD, MPH, Assistant Professor of Neurology at Vanderbilt University School of Medicine in Nashville. The system that St. Jude Medical introduces to the market may be different from the one that was approved, she added.
Evolving Technologies
Other new DBS devices also are in development. Boston Scientific is refining its Vercise Primary Cell DBS system, which has an eight-contact lead. All eight contacts may not touch the desired target in the brain (eg, the subthalamic nucleus), but research indicates that stimulating areas outside the target may benefit the patient, said Dr. Phibbs. The Vercise system also enables current steering; each of the eight contacts has an independent current source, and the neurologist thus has flexibility in adapting the field of stimulation.
In addition, researchers are investigating devices that allow directional stimulation through current contacts in the form of rings, which ensure that the stimulation is emitted uniformly. Directional stimulation, however, can bring benefits to one area, but cause side effects in another area. One method of avoiding this result could be to develop a fractionated lead that allows the neurologist to turn on only two sides of the contact. “In theory, it sounds great,” said Dr. Phibbs. But “the thought of programming something like that makes me a little bit anxious.”
Future Applications for DBS
The closed-loop feedback system may represent the future of treatment for movement disorders, said Dr. Phibbs. Such a system would deliver stimulation in response to a specific condition, such as changes in the neuronal firing patterns (eg, the beta band on microelectrode recording). Investigators have considered the feasibility of treating Parkinson’s disease and other movement disorders with the NeuroPace device, a responsive neurostimulator approved for treating epilepsy. The battery of the NeuroPace device, however, “can’t supply the stimulation levels that we require,” said Dr. Phibbs, but researchers are attempting to overcome this obstacle.
The literature contains several reports of DBS providing benefits for patients with Tourette’s syndrome, and the therapy may be appropriate for exceptionally severe cases. “The difficulty is target selection,” said Dr. Phibbs. The appropriate target in the brain is a subject of debate, but the ventral capsule/ventral striatum may be appropriate because of its association with obsessive–compulsive disorder (OCD), which often is comorbid with Tourette’s syndrome. The proper programming for the DBS also is unclear. “It’s a very difficult patient population to deal with. You need to have really good psychiatric backup as well because the OCD component for the Tourette’s can be so disabling for patients.”
In the ADvance study, researchers are examining the potential cognitive benefit of DBS in patients with Alzheimer’s disease. Investigators in the United States and Canada administered DBS to the hypothalamus and the fornix, and participants received regular physiologic, psychologic, and cognitive assessments for 12 months. Initial study results were reported at the Alzheimer’s Association International Conference 2015. Other researchers are investigating whether administering DBS to the nucleus basalis of Meynert could improve cognition in patients with Alzheimer’s disease.