Another benefit of the stimulation therapies, experts argue, is their deft aim. "They get to the brain more directly than medications," says Mehmet Dokucu, a psychiatrist who is director of the Cancer Psychiatry Service at the Feinberg School of Medicine at Northwestern University. He administers transcranial magnetic stimulation (TMS) and electroconvulsive therapy (ECT) to treat patients with severe depression. He also administers ECT to Parkinson's patients and people with mania that is followed by a catatonic state. Current medications, he adds, "hit a very broad swath of the body and the brain"—a fact that can make for side effects, including dry mouth, lethargy, diminished libido, agitation, or suicidal thoughts. But brain stimulation therapies are not without their own side effects, which can range from headache to memory loss to death. (Death is always a risk—though a relatively small one—with surgical procedures, too.)
To be sure, patients shouldn't expect a doctor to be flip about recommending a brain stimulation therapy. "Typically, we address [a patient's illness] first with medications, psychotherapy, exercise, dietary changes," Dokucu explains. "Neurostimulation is a second-, third-, or fourth-line treatment." And sometimes drugs might be used in combination with brain stimulation, even though they may not have worked previously, to maintain gains from the stimulation.
Getting treated with ECT or TMS involves a series of visits to get the therapy—a few times per week, say, for three to five weeks. That is not the case with the implanted devices used in DBS and VNS, though several separate procedures are required for DBS. While arguably less invasive than surgery, a series of treatments with TMS or ECT can provide only temporary results and, even when covered by insurance, may cost several hundred dollars in copays per treatment.
While no one knows the limits of brain stimulation's therapeutic potential, research on neuromodulation is certainly exploding. That's partly because of the potential financial upside for successful device-makers.
No matter how optimistic researchers may be, patients seeking relief through relatively new or experimental applications of brain stimulation need to have measured expectations and exercise caution.