Trigeminal nerve stimulation (TNS) is an experimental device that shows promise in treating epilepsy. It might someday be available to treat severe depression in patients whose illness has not responded to antidepressants or psychotherapy. In clinical trials for TNS, electrodes are taped to a patient’s forehead and then connected to an electrical stimulator specifically designed to target the trigeminal nerve. This nerve is responsible for passing sensory information between the central nervous system and the face.

The precise mechanism by which TNS might lessen depression is not currently understood. Much scientific research needs to be done before TNS would become available for treating either depression or epilepsy outside of clinical trials.

How Trigeminal Nerve Stimulation Works

During TNS, a patient wears an external stimulator that is about the size of a large cell phone. The stimulator is connected to wires that lead to electrodes on top of conductive pads attached to the forehead. The electrodes, which can be covered by a cap or scarf, transmit electrical stimulation to the trigeminal nerve, which extends from the brain out into the muscles and skin of the face.

TNS is currently an experimental procedure, but researchers think that wearing the stimulator regularly for eight hours overnight should be adequate to control depression. Patients have described a tingling or buzzing when wearing the stimulator, but these do not interfere with sleep.

TNS differs from electroconvulsive therapy—an older, proven method of treating severe depression—in that the electrical energy does not travel directly into the brain but, rather, stimulates a specific nerve.

Who It’s For

At this point, trigeminal nerve stimulation is experimental, so only patients enrolled in a clinical trial can receive it. A small double-blind clinical trial is underway. This means that neither the patient nor the doctor will know the exact dose of electricity a specific patient has been receiving until after the clinical trial is completed. The researchers avoided enrolling any patients in the clinical trial who had skin irritation on the forehead where the electrodes must be taped. Also, they did not enroll any women who were pregnant or nursing. However, the researchers believe that TNS might someday be a good therapy for pregnant or nursing women with major depression because it is not a drug that could cross the placenta or enter breast milk. Much further research is needed to know for sure.

Possible Side Effects or Complications

No large-scale clinical trials have established the safety or even the effectiveness of trigeminal nerve stimulation in treating depression. So it’s impossible to fully understand the possible side effects or complications of this experimental treatment. In a recently completed pilot study, two out of 11 patients developed mild skin irritation on their foreheads where the electrodes were attached.

In theory, TNS would not cause side effects common to other depression treatments. For example, TNS is a not a drug therapy, so the weight gain and sleep disturbances antidepressants can cause should not occur. Unlike electroconvulsive therapy, TNS does not induce seizures, so the memory problems sometimes associated with that treatment would not be a factor. And TNS does not require general anesthesia, another risk involved in treatments such as deep brain stimulation and vagus nerve stimulation.

What the Expert Says

Because trigeminal nerve stimulation is experimental and won’t be available to patients for several years at least, physicians who are not involved with the TNS clinical trials are not yet familiar enough with this treatment to comment on its potential.

TNS was invented and is being developed at the University of California Los Angeles (UCLA). The university has executed an exclusive worldwide license for the TNS machine with a company that specializes in technology commercialization. The UCLA research team has presented TNS findings at scientific conferences and published articles in peer-reviewed medical journals.

Ian Cook, M.D., the Joanne and George Miller & Family Chair in Depression Research at the UCLA Brain Research Institute, leads the TNS clinical trial on depression. “Depression is so common and disabling for many people; we need more treatments,” Cook says. “Having a very different treatment option like TNS—we call it a gentle USB port to the brain—could be a real asset to patient care. But any new treatments need to be evidence-based and FDA-cleared. We hope this will happen in the next few years.”