The Food and Drug Administration this week considers whether a procedure called transcranial magnetic stimulation (TMS) lifts depression. The FDA will also examine new evidence on a therapy they've already approved, called vagus-nerve stimulation. VNS uses electrical current to stimulate the brain. Both of these treatments are targeted at the small number of patients who don't respond to antidepressant drugs or psychotherapy.
Psychiatrists are divided about these two therapies. Paul Holtzheimer of Emory University has done some research paid for by the TMS manufacturer and he was involved in a government-funded evaluation of a TMS system. In TMS, use an electromagnetic frequency to stimulate specific areas of the brain.
In that study, 68 patients sat under the electromagnet. Everyone thought they were getting the treatment, but only half did. For some, the magnetic field was aimed away from the head.
"We showed a 30 percent difference vs. a 6 percent difference in the sham group, and that was, we felt, clinically significant," Holtzheimer says. "And we talked to the patients, and for those patients who got better, it was a very meaningful change, and that was in a group of patients we didn't expect to get better with just another medication."
Holtzheimer has also had patients who opted for the other approach being considered by the FDA, vagus-nerve stimulation.
In this therapy, a small wire is attached to the vagus nerve, which comes out of the brain stem. An electrode placed around the nerve delivers stimulation to that nerve, which feeds back to the brain.
"It's a form of brain stimulation from a remote location," Holtzheimer says.
It requires surgery to implant the battery and wire. When the FDA approved vagus-nerve stimulation for depression in 2005, it was a controversial move. The initial data submitted by the company didn't show any clear evidence that there were any benefits after three months of treatment. At the time, FDA staffers advised against approval. Then the company did more testing, this time without comparing to a placebo or another treatment. After another evaluation, the FDA approved it. Still, most insurers, including Medicare, aren't paying for it. Friday, the FDA will look at how the procedure is working in the real world.
Wayne Blackmon, a Washington, D.C. psychiatrist, is among a group of psychiatrists who think it should never have been approved.
"Although there is some promise that appears to be held out by some studies, the studies backing the use of VNS for severe depression really are inadequate, and it's really not ready for prime time," Blackmon says.
He doesn't agree with psychiatrists who say that given the real risk of suicide among these patients, the FDA approval was justified.
"VNS is an invasive procedure, so you expose people to risks without any clear-cut benefit beyond placebo," Blackmon says.
Blackmon is open to the magnetic stimulation therapy. He points out that TMS doesn't require surgery, has no significant side effects, and is cheaper.
On Friday, FDA advisors will weigh in on both these therapies. Meanwhile, a third therapy that involves putting electrodes deep inside the brain, called deep brain stimulation, is still in testing.