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The Food and Drug Administration (FDA) yesterday approved a brain implant intended to help control some symptoms of dystonia, a rare, debilitating movement disorder. The device was approved for treating primary dystonia, the type that has no known cause.
Dystonia causes sustained, simultaneous muscle contractions that force the affected body parts into abnormal and sometimes painful postures and movements.
This deep brain stimulator, made by Medtronic, Inc., of Minneapolis, Minn., was already approved for treating Parkinson’s disease and essential tremor. Yesterday’s approval broadens its use to people with primary dystonia who get little or no relief with medication.
The product is the Activa Dystonia Therapy System. The system consists of electrodes and a neurostimulator. The electrodes are implanted into the brain and connected by leads (wires) under the skin to the neurostimulator implanted in the chest.
The neurostimulator sends a constant stream of tiny electrical pulses to the brain, suppressing symptoms. When the device is implanted in both sides of the brain, two separate systems are used.
To turn the stimulator on and off, the patient touches a hand-held magnet over the neurostimulator. The neurostimulator must be replaced every three to five years, the lifetime of the battery.
FDA approved the product through a special regulatory process--known as a humanitarian device exemption--designed to encourage the development and marketing of medical devices for people with rare conditions, i.e., those affecting 4,000 or fewer people a year. The manufacturer of such a product must show that the device is safe and has a probable benefit for the patient.
FDA based approval of the Activa Dystonia Therapy System on a review of 34 scientific case studies in which 201 people with primary or secondary dystonia had the device implanted and received deep brain stimulation.
Unlike primary dystonia, which has no known cause, secondary dystonia is caused by an underlying disease such as Parkinson’s, a brain tumor or a stroke. The patients in the studies were followed for approximately one year.
In several cases, patients with primary dystonia reported improvement in movement and in activities of daily living after deep brain stimulation. Patients with secondary dystonia experienced little or no improvement. The most common side effect was infection.
Although some patients across the studies benefited from the Activa system, individual results varied in each study, and the specific benefit for an individual cannot be predicted. However, because of the debilitating nature of dystonia and the lack of other effective treatments, FDA believes that the probable benefit to health for people with primary dystonia who get no relief with medication outweighs the risk of illness or injury.
FDA is committed to making safe and effective new medical technologies available quickly to American patients.
Around 2,000 people a year in the United States are expected to be candidates for this device.
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