Expanded use of brain implant

FDA Consumer, July-August, 2003

People who experience the sustained, simultaneous muscle contractions of the rare movement disorder called dystonia now have another treatment for the condition, which forces affected body parts into abnormal and sometimes painful postures and movements.

The Activa Dystonia Therapy System, a brain implant already used to treat Parkinson's disease and essential tremor, was approved by the FDA in April to treat dystonia. The deep brain stimulator is manufactured by Medtronic Inc. of Minneapolis.

The system consists of electrodes and a neurostimulator. The electrodes are implanted into the brain and connected by wires under the skin to a neurostimulator implanted in the chest. The neurostimulator sends a constant stream of tiny electrical pulses to the brain, which suppresses symptoms. When the device is implanted in both sides of the brain, two separate systems are used. Patients touch a hand-held magnet over the neurostimulator to switch the device on and off.

The most recent approval broadens the use of the device to people with primary dystonia who get little or no relief with medication. Primary dystonia has no known cause, unlike secondary dystonia, which is caused by an underlying disease such as Parkinson's, a brain tumor, or a stroke. Results in patients using the device varied, and the specific benefit for an individual cannot be predicted. But because of the debilitating nature of dystonia and the lack of other effective treatments, the FDA has determined that the probable health benefit for people with primary dystonia who get no relief with medication outweighs the risk of illness or injury from the device.

The FDA approved the device through a special regulatory process known as a humanitarian device exemption, which is designed to encourage the development and marketing of medical devices for people with rare conditions.