Parkinson's Disease: Can TMS Help?
A review of the evidence, and hope for the future, from excellent design.
Parkinson’s Disease (PD) is a neurodegenerative condition that leads to problems with both movement and thinking. This newsletter is daily enough and health-themed, and I woke up thinking about movement disorders. Thus, this article!
It's a disable condition in which not enough dopamine is made by the cells normally responsible for that. This dopamine-producing center of the brain, called the substantia nigra is unable to keep up with the brain’s need for dopamine. Dopamine is not the only chemical that makes us “feel good.”
As I have written in Inessential Pharmacology (Amazon link), dopamine is an essential regulator in several neural circuits. These circuits impact motor functioning, pleasure, reward-seeking, attention, and prolactin release, among other brain functions.
One of the themes of this newsletter, over and over again, is that the brain’s function is more about circuits than chemicals. Today, I'm discussing Parkinson's disease and the role of non-invasive neuromodulation with transcranial magnetic stimulation and trandcranial direct current stimulation (tDCS) as additional treatment options for those suffering from Parkinson's disease.
First and foremost, Parkinson's Disease leads to problems with movement. As their ability to manufacture dopamine falls off, their ability to move is inhibited. Their gate gets slower, and their movements become stiff, rigid, and inflexible. All of the muscles, tendons, and bones work the same. It's a problem with the neural control of those movements—but it means people suffering get frozen. There can be cognitive problems as well as the disease advances, and eventually even dementia for some.
In the Journal of Neurological Sciences, at the end of last year, a lovely meta-analysis of the effectiveness of both TMS and tDCS was published as it related to the cognitive deficits of the disorder1. I’m going to skip over the many years of Deep Brain Stimulation work for now, except to say— it’s effective!
The results of that meta-analysis were not encouraging. They reviewed every study between 2000 and 2023 and found…nothing:
After database searching and screening of texts, sixteen studies met the inclusion criteria. No significant results emerged from any investigated cognitive domain when comparing NIBS and sham treatments.
Well…case closed. It just doesn’t work! Except…maybe we are missing something? Another group of authors (Zhang et al.)2 , on January 6th of 2025, mere months after Giustiniani et al., completed the meta-analysis mentioned above.
One of the major issues that comes up, again and again, in this field is the low quality of the studies:
12.5% (2/16) of the SRs rated as high quality, 43.75% (7/16) rated as low quality, and 43.75% (7/16) rated as very low quality
Further:
Using the GRADE system, 16 papers were analyzed for 62 outcome indicators. The findings revealed that there was no high quality evidence present in the SRs.
At a high level, the GRADE system evaluates factors that increase or decrease the possibility that the data you are considering are not bull$*&#.
This includes risk of bias, inconsistency, indirectness of evidence, imprecision—remember those confidence intervals I’m always including?—and publication bias. That, of course, is the likelihood that journals publish positive results and keep negative outcomes on the shelf.
Zhang et al. found that, among this steaming pile of not-good-enough data in PD studies, at least motor symptoms were improved—across both lower limbs and arms. There is also a “Timed up-and-go” test, which uses the amount of time it takes someone suffering to get up from a chair and start walking. This is at once a useful measure—in that it outputs a scalar variable (in seconds)— and a very sad thing to contemplate. As someone with occasional mobility problems,
Chen et al.3 , in their 2021 meta-analysis, found significantly improved short-term upper limb function and short-term and long-term walking performance. Again, having your arms and legs work is a big deal. Virtually everyone with Parkinson’s Disease used to be able to use their arms and legs as they saw fit. That was their entire life. When the disease hits, that “ease” of movement is removed.
The early evidence says TMS can help with these problems. One of the issues is that TMS hasn’t been studied in enough high-quality studies. Another is that TMS has, at least until now, only been available in clinics you’d have to walk to. If you have a mobility problem, getting to the clinic becomes non-trivially difficult.
We need better-designed studies and more portable TMS, and these are both design problems. Colleagues, including Dr. Jonathan Downar, have recently announced one approach to solving this problem. I’ve covered some of his team’s work previously—remember that One-Day Depression Treatment? Well, the company he co-founded to bring more TMS to the world, Ampa Health, is now out of stealth!
They built a light, (relatively) cheap, and portable machine that is easy to use and can be moved by one person in the trunk of their car!
It’s got a camera in the stimulator that makes it easy to target and an extremely well-designed cap with targets marked to make it easy to deploy with limited training.
Ampa dropped this email in my inbox, so I’m sharing a sneak peek with you:
It’s a triumph of design. I hope better-designed devices that are easier to bring to patients will make a real difference—not just in depression, but especially in disorders where mobility is a serious barrier, like Parkinson’s Disease.
I’m thrilled to announce Ampa Health will be joining us at RAMHT ‘25 on May 18th in Los Angeles, right alongside the APA Annual Meeting.
Thank you for reading! If you are a health professional interested in the Ampa technology, you can book a demo here. The Ampa device isn’t cleared for the treatment of PD yet—no TMS treatment is. In order to get to that level of evidence, we will need design thinking—both for our devices and for our studies.
Giustiniani, A., Maistrello, L., Mologni, V., Danesin, L., & Burgio, F. (2025). TMS and tDCS as potential tools for the treatment of cognitive deficits in Parkinson’s disease: A meta-analysis. Neurological Sciences, 46(2), 579-592.
Zhang, L., Jiang, Y., Fan, W., & Xue, H. (2025). Unveiling the efficacy of repetitive transcranial magnetic stimulation in Parkinson’s disease: A comprehensive review of systematic analyses. PloS one, 20(1), e0313420.
Chen, J., He, P., Zhang, Y., Gao, Y., Qiu, Y., Li, Y., ... & Wang, L. (2021). Non-pharmacological treatment for Parkinson disease patients with depression: a meta-analysis of repetitive transcranial magnetic stimulation and cognitive-behavioral treatment. International Journal of Neuroscience, 131(4), 411-424.