Using Magnetic Fields to Treat Alzheimer’s Disease
Post by Christopher Chen
The takeaway
Repetitive transcranial magnetic stimulation (rTMS) can be used as a noninvasive therapy to alleviate some symptoms of Alzheimer’s disease (AD). Applying rTMS to a brain region called the precuneus of patients with AD may slow the disease’s progression and even enhance brain activity in the precuneus itself.
What's the science?
In Alzheimer’s disease (AD), a specific network in the brain called the default mode network (a group of brain regions that are functionally connected) undergoes pathological changes that underlie AD symptoms. The precuneus is a brain region found in the posterior cortex and is one of the primary brain regions included in the default mode network. Research shows that the precuneus is one of the earliest regions within the brain to display amyloid plaques and neurofibrillary tangles, well-known markers of AD. Unsurprisingly, research also links these pathologies to compromised precuneus function, resulting in overall dysfunction in the default mode network. Thus, restoring precuneus activity and connectivity to the default mode network may provide therapeutic benefits to patients with AD. rTMS, which provides indirect magnetic stimulation to specific parts of the brain, has been shown to restore cognitive function in patients with mild forms of AD when applied over a short (two-week) period. Recently in Brain, Koch and colleagues explored whether long-term application of rTMS to the precuneus carries therapeutic value to patients with AD.
How did they do it?
The study consisted of fifty patients with mild to moderate forms of AD. All patients had been prescribed an independent pharmacological treatment for AD. Before the study, the patients were given a battery of assessments designed to measure cognitive function by a team of clinicians and researchers. Following these assessments, patients were divided into the experimental group which would receive rTMS to the precuneus, and the control group which would receive a procedure that resembled rTMS but was not (sham control).
In the first two weeks of the experiment, all patients received extensive experimental or sham rTMS treatment five times a week. The final twenty-two weeks was the maintenance period where patients received experimental or sham treatment once a week. This maintenance period also included a mid-study assessment of cognitive function at twelve weeks. Following the six-month period, patients underwent a final round of assessments to measure cognitive function. Single-pulse TMS combined with EEG was also used to assess precuneus activity and oscillatory activity.
What did they find?
Researchers compared scores from all clinical and behavioral assessments as well as functional readouts from brain imaging assessments in the experimental and sham groups. While both groups showed a generalized decrease in performance on the cognitive tests over time, patients in the experimental group showed smaller decreases on every cognitive assessment both at the mid-study (twelve-week) point and end-study (twenty-four week) point. The brain imaging assessments – which measured precuneus signaling activity using a noninvasive electroencephalogram (EEG) – revealed significant differences in precuneus activity between experimental and sham groups. In fact, the experimental group showed an increase in precuneus activity following the study’s conclusion.
What's the impact?
While short-term rTMS has been used to alleviate AD symptomology, this study is the first to examine its effects over the long term. Additionally, rTMS treatment in AD patients has been largely focused on the prefrontal cortex, not the precuneus, a region of the brain known to exhibit some of the earliest signs of AD pathology. Based on the beneficial changes precuneus-specific rTMS treatment had on patients with AD, this study shows that the precuneus may be a compelling therapeutic target for AD treatments.