Medtronic has conducted a large-scale randomized trial for deep brain stimulation on epilepsy. Data will be submitted to the FDA this year, says Paul Stypulkowski, senior director of therapy research of Medtronic.
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The data, presented in December at a meeting in Seattle, show that deep brain stimulation reduced the number of seizures by 38% compared with what was seen before implanting the device.
That is slightly better than improvement seen with vagus nerve stimulation, another FDA-approved electrical stimulation treatment, which reduces seizures by about 25%.
The control group whose device was kept turned off, also improved, by 14.5%. That could be due to a placebo effect. Or it might be because people who join trials are usually at their worst -- and often tend to improve somewhat on their own, says trial researcher Dr. Douglas Labar, of the Weill Cornell Medical College in New York.
If deep brain stimulation is approved, Labar says, patients will have the choice between a more efficient but also more risky treatment and the slightly less efficient but also less risky vagus nerve stimulation.
Medtronic and a second company, St. Paul, Minn.-based St. Jude Medical, have two large-scale randomized trials underway for severe, treatment-resistant depression. (St. Jude Medical recently received approval to sell its device for the treatment of Parkinson's disease in Europe and is now completing studies aimed at securing FDA approval for treating Parkinson's and another movement disorder in the U.S.)
Medtronic's depression trial will follow about 200 patients stimulated in an area called the anterior limb of the internal capsule for at least one year.
This brain target for depression was identified by accident: When obsessive-compulsive disorder patients who also had depression were stimulated in this area, their depression also improved.
In one case, a patient produced a one-sided smile when stimulated on one side of the brain and also expressed feelings of happiness, says study researcher Dr. Wayne Goodman of the National Institute of Mental Health.
In a recently published unblinded study, about half of 15 patients showed at least a 50% improvement in severe depression symptoms a year or more after surgery when the anterior limb of the internal capsule was stimulated, says Rezai, who was involved in the study.
St. Jude Medical chose a different brain target, area 25, for its depression trial, which will enroll more than 100 patients. Brain imaging studies have shown that area 25 is more active in depressed people.
In a study of 20 patients, 55% still responded to treatment as late as one year after surgery, says study author Dr. Helen Mayberg, professor of psychiatry and neurology at Emory University. That is an "unheard-of response rate" given that these patients had tried and failed every other treatment, including several medications and electroconvulsive therapy, Mayberg says.
By comparison, Mayberg says, stimulation of the vagus nerve in the neck, approved by the FDA for depression, has only a 15% response rate at 10 weeks in similarly severely depressed patients.
Dr. Thomas Schlaepfer, vice chairman of the department of psychiatry of the University of Bonn in Germany, has been treating severely depressed patients by stimulating yet a third brain target, the nucleus accumbens.
The nucleus accumbens doesn't show normal activity in depressed patients, which could explain why they are less able to experience pleasure.
Last year, Schlaepfer showed that deep brain stimulation in this area led to acute improvements in three severely depressed patients. He says he has extended the work to 10 patients, half of whom showed an improvement when examined a year later.
With deep brain stimulation now being tried in at least three brain areas for depression, the question is, which target is the best? All agree that it's too early to tell.