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ATLANTA -- Patients with dystonia, a neurological disorder characterized by involuntary and sometimes painful muscle contractions and contortions, can now more easily receive a treatment known as deep-brain stimulation (DBS) to control their movements. Late yesterday, the U.S. Food and Drug Administration (FDA) announced approval under a Humanitarian Device Exemption (HDE) for Medtronicís so-called "brain pacemaker" for use in patients with severe and disabling forms of dystonia. The treatment, often called Activaģ Therapy, has already received approval by the FDA to treat Parkinsonís disease and Essential Tremor, the two most common movement disorders.
"This approval should make DBS more accessible for patients with dystonia," says Jerrold Vitek, MD, PhD, professor of neurology, Emory University School of Medicine. "Our hope is that with this approval, this treatment option will be brought to the forefront as an adjunctive therapy while increasing awareness to patients and their physicians. Deep-brain stimulation has been used for years to treat the symptoms of Parkinsonís disease, and still many Parkinsonís patients are not aware of this therapy. Even fewer dystonia patients know that DBS is an option for their condition."
Dystonia is the third most common movement disorder behind Parkinsonís disease and Essential Tremor. According to the Dystonia Medical Research Foundation, the condition affects approximately 300,000 people in North America. Dystonia can affect many parts of the body including the arms, legs, neck, trunk, eyelids, face and vocal cords, but it does not affect intellect.
Emory has been using deep-brain stimulation to treat dystonia for just over five years, and in that time, 17 cases have been performed here. In fact, the first U.S. deep-brain stimulation for dystonia case to be reported in scientific literature was done at Emory. Approximately 60 cases have been performed throughout the U.S. since 1997.
Doctors often recommend DBS to patients who do not respond well to medications, have severe side effects from medications or who have developed an immunity to Botox injections. Since there is no known cure for the disease, DBS represents a viable treatment option for these patients.
Deep-brain stimulation works by delivering controlled pulses of electrical stimulation to the region of the brain that is not functioning properly. Neurosurgeons implant a lead - a thin, metal wire with four electrodes at the tip - in a precisely targeted area of the brain that controls movement. Then the lead is connected to a battery-operated pulse-generating device, similar to a cardiac pacemaker, though a second wire tunneled from the scalp to the chest, where the device is implanted. Following surgery, doctors program the device to set appropriate stimulation levels for each individual case. Medtronic, Inc., headquartered in Minneapolis, Minnesota, is the maker of these products.
A HDE allows approval of a device for conditions that are considered rare. The approval is granted with the understanding that the device is intended to benefit patients in the treatment and diagnosis of diseases or conditions that affect or is manifested in fewer than 4,000 people in the U.S. per year. Regulators base the exemption on devices that have shown good results in other similar conditions, while showing positive results in clinical trial settings for the particular condition in which it is being approved. The HDE allows patients to seek treatment more quickly, rather than waiting for individual approval from a medical centerís review board for use of each investigational device.
"We should now be able to offer DBS to patients with dystonia in a more timely manner, since a formal approval is no longer needed to implant the device," says Dr. Vitek, a long-time dystonia researcher. Medicare may also be more willing to cover the procedure because of the HDE. Previously, Medicare has decided whether to cover DBS for dystonia on a case-by-case basis.
Activa Therapy -≠ or DBS -- for the treatment of Essential Tremor received FDA approval in 1997. Approval was granted in 2002 for its use in the treatment of advanced Parkinsonís disease. Under the FDAís HDE, deep-brain stimulation for dystonia is available to adults and children seven years of age and older for the treatment of chronic, intractable (drug resistant) dystonia, including generalized (affecting the entire body), segmental (affecting two areas of the body that are next to each other), hemidystonia (affecting one half of the body) and cervical (affecting the neck and head). An estimated 2,400 Americans each year are diagnosed with forms of dystonia that may be treatable with Activa Therapy.