Published: June 28, 2011
Updated: June 28, 2011
When Sarah Hollingsworth Lisanby, MD, joined Duke as the new chair of psychiatry last October, she brought with her a prodigious lab that has been instrumental in developing new devices for psychiatric disorders.
Among them is a form of brain stimulation called transcranial magnetic stimulation (TMS), which, thanks to a study led by Lisanby, earned FDA approval in 2009 as a treatment for depression in patients who have failed medical therapy.
“TMS has been around since 1985 as a neuroscience tool,” says Lisanby, and recent advances in bioengineering have allowed TMS to transition from a basic tool of discovery to a therapeutic application. It works on the principle of electromagnetic induction, through which magnetic fields induce electrical fields.
“Powerful magnets that are turned on and off very rapidly will induce a small electrical eddy current in a conducting medium,” Lisanby says -- and the fluid-filled brain is the perfect medium. There’s a network of brain areas that are underactive in depressed patients, says Lisanby.
“It’s not as crisply defined as the neural loop in motor disorders,” she says, noting the wide array of life experiences and biological pathways that feed into each individual case of depression. “But functional imaging shows us that this same network of brain areas comes up again and again in depression patients. If we can go in and change the function of these areas, perhaps we can affect depression like DBS does for motor disorders.”
Shaped like a paddle and held on the head, the magnetic coils of the TMS device send a magnetic field through the skull that stimulates an area of the brain beneath the left side of the forehead known as the left dorsolateral prefrontal cortex.
Making that area more active can reduce symptoms of depression in some patients -- in the clinical trial led by Lisanby, patients who received TMS had greater declines in symptoms (as measured by Montgomery-Åsberg Depression Rating Scale, Clinical Global Impression Severity of Illness Scale, and Inventory of Depressive Symptoms–Self-Report scores) than patients who did not.
The effects of TMS are moderate, and about the same order of magnitude as that seen with antidepressant medications, though less significant than those of electroconvulsive therapy (ECT) -- which uses much stronger electrical current to induce a brain-wide seizure in order to alleviate depressive symptoms.
Also unlike ECT, TMS is completely noninvasive; during the hour-long treatment, the patient sits in a reclining chair and does not need anesthesia. It hasn’t been found to affect memory or cognition, and the side effects -- such as scalp discomfort or headache -- are generally mild.
Typically, patients go for one-hour sessions daily for a series of weeks, and then follow up with medication or continued, less frequent TMS. The effects of the treatment also last for several months, and Lisanby says the repeated doses may help make the brain more amenable to future treatment.
“When a person does anything repeatedly, like practicing the piano or trying to memorize a sequence of behaviors, the person is repeatedly using a particular circuit,” she explains. “This is the concept of neuroplasticity: repeatedly using a circuit makes it easier to engage that circuit in the future.”
Lisanby considers TMS a solid step toward developing new and newly effective angles for treatment of depression. “Refractory depression is a very serious illness, and we need more technologies for these kinds of disorders,” she says.
“TMS is radically different from current treatments for depression, and we want physicians to know that TMS is out there as an option for patients who are suffering from depression and for whom other treatments were intolerable or ineffective.”
Lisanby and her team are also studying ways to make magnetic stimulation more effective through the induction of focal seizures. This technique, called magnetic seizure therapy (MST), was developed by Lisanby’s team and promises to retain the efficacy of ECT, the most effective treatment for depression, but without the undesirable side effect of memory loss.
Clinical trials on MST are under way now at Duke and other universities in the United States, Europe, and Australia.
Duke offers a weekend CME training on TMS that includes didactics and hands-on training. For more information, contact Rosa Jou-Zhang at email@example.com or visit the Office of Continuing Medical Education Web site.
To refer a patient for TMS, or for a research study involving brain stimulation, contact Lis Bernhardt at firstname.lastname@example.org or call 888-ASK-DUKE.