Transcranial magnetic stimulation, or TMS, is a procedure that uses magnetic fields to stimulate nerve cells in the brain.
The therapy was first approved by the U.S. Food and Drug Administration as a treatment for major depression in 2008. In 2013, the FDA expanded its use for pain associated with certain migraine headaches. Though it is a noninvasive treatment for depression and pain — types of illnesses associated with brain functioning — the FDA has not approved it as a therapy for treating dementia.
Yet TMS is among a growing family of brain stimulation techniques being researched and developed to possibly treat multiple neurocognitive disorders, including Alzheimer's disease.
TMS has received the greatest attention in clinical research on neuropsychiatric disorders. Though the benefits of TMS are not well understood, there is a general agreement that brain stimulation can be modified by the repetitive delivery of a high-intensity magnetic field, generated by passing electrical current through an inductive coil.
It is believed that TMS might benefit those affected by Alzheimer’s because of the effects on the depressive symptoms they often simultaneously experience. It's estimated that about 50% of people with Alzheimer's suffer from depression, and even mild depressive symptoms are associated with significant impairment of cognitive functions.
Improvement in Alzheimer's symptoms following TMS results from alleviated depressive symptoms, it is difficult to judge whether it works. But it's notable that treated individuals sometimes also exhibit elevated mood, scoring better on depression and apathy scales. So it is plausible that because TMS is an effective therapy for major depression, it might be equally successful in cognitive improvement.
Important issues surround the potential application of repetitive TMS in Alzheimer’s disease. An FDA review in 2019 identified several deficiencies that need to be addressed. These included an uncertainty around the reporting of adverse effects, the failure to demonstrate a clinically meaningful benefit in the disease and that insufficient data documenting the benefits of the therapy outweighed its health risks.
Additionally, longer-term risks have not been considered. TMS therapy research is still preliminary and cautious interpretation is warranted, researchers say.
TMS is a promising possibility for future Alzheimer’s therapy as the urgent need for the development of new, effective strategies continues.
According to the 2020 Alzheimer’s Facts and Figures, based on updated calculations, an estimated 6.2 million Americans aged 65 and older are living with Alzheimer’s dementia. In the absence of effective interventions for disease prevention or slowing, the projected burden represents a looming health care crisis as the population ages.