Further to my recent post on DBS (deep brain stimulation), it has been pointed out to me that the brain can be stimulated without surgery to implant a stimulation device. Naturally, the effects of external stimulation are less – and, I imagine, are rather awkward to administer – but at least there is no brain surgery involved.
How effective are these procedures?
(And if you want to skip the academic science-y bit, I’ve included the following options:
- Click here to go straight to my answer to the above question
- Click here to go straight to the fun, “Wow, tDCS is cool!” bit)
I found a pair of articles that seem to address precisely this question. They are both from the same team; the first (from 2005), is a review of existing literature and is available in full. The second (from 2007) is another review, this time with an emphasis on the therapeutic potential. Only the abstract of this second paper is free to view. Both articles look at forms of magnetic and electrical stimulation.
The first article sets out its stall in the abstract:
A systematic review and meta-analysis were conducted to quantify the efficacy of transcranial magnetic stimulation (TMS) and electroconvulsive therapy (ECT) for the treatment of motor dysfunction in patients with Parkinson’s disease (PD).
and summarises its conclusions:
[…] TMS, across applied stimulation sites and parameters, can exert a significant, albeit modest, positive effect on the motor function of patients with PD. ECT also may exert a significant effect on motor function in PD patients.
F Fregni, D K Simon, A Wu, A Pascual-Leone,
“Non-invasive brain stimulation for Parkinson’s disease: a systematic review and meta-analysis of the literature”
J Neurol Neurosurg Psychiatry 2005;76:1614-1623 doi:10.1136/jnnp.2005.069849
Maybe it’s just me, but the idea of ECT is not terribly appealing. Even without the potential for convulsions, there is an association with the involuntary treatment of institutionalised psychiatric patients. Maybe my brain is deficient, but my mind is still working… but it has to be said that if the treatment were proven to have long term beneficial effects on my condition, I would consider it; after all, Wikipedia implies that it might not be that bad (although literary types seem not to be very keen – maybe that explains the negative portrayal I have encountered in novels).
So far as Fregni’s review is concerned, however, the evidence of beneficial effect on Parkinson’s is shaky, not least because of a lack of relevant acceptable studies.
The initial part of the paper itself describes how the researchers located, extracted and compared the data from the various studies. Their criteria for inclusion seems to have been satisfyingly thorough; for example, many of the articles they found were case studies and were deemed inadmissible (because too few patients were included). In the latter part of the paper, they discuss their findings and note:
The result of this meta-analysis opens up an avenue for the exploration of electrical stimulation. For example, studies are needed to assess the efficacy of new methods of brain stimulation in PD patients. Transcranial direct current stimulation is one of these therapies which might be valuable in PD. Recent studies have shown that this therapy can induce modulatory effects in the brain cortex similar to those induced by rTMS.
They also talk about “Cortical (epidural) stimulation” as being another promising therapy for PD:
A case report and animal study showed that epidural motor cortex stimulation may be a good approach to improve symptoms of PD and the benefits may be longer lasting than those following rTMS.
This is something that I haven’t spotted elsewhere. However, I’m not following it up right now because this blog post is getting rather too long already…
The 2005 paper concludes by stating that:
[…] our findings encourage further larger and carefully designed clinical trials to assess the potential clinical value of rTMS for PD patients.
Two years later, the group had shifted their focus from ECT to tDCS, but were still interested in rTMS. The abstract of the 2007 paper doesn’t give much away. It states that:
[…] brain stimulation techniques tailored to modulate individual plastic changes associated with neurological diseases might enhance clinical benefits and minimize adverse effects.
and goes on to say:
In this Review, we discuss the use of two noninvasive brain stimulation techniques — repetitive transcranial magnetic stimulation and transcranial direct current stimulation […] We review randomized controlled studies, in focal epilepsy, Parkinson’s disease, recovery from stroke, and chronic pain, to illustrate these principles, and we present evidence for the clinical effects of these two techniques.
Felipe Fregni & Alvaro Pascual-Leone,
“Technology Insight: noninvasive brain stimulation in neurology—perspectives on the therapeutic potential of rTMS and tDCS”
Nature Reviews Neurology 3, 383-393 (July 2007) | doi:10.1038/ncpneuro0530
I don’t want to take that “evidence for the clinical effects” to mean “positive evidence for the clinical effects”, but the previous paper had suggested that there were modest benefits. I found a number of other interesting articles that cited the work of Fregni et al, the most pithily pertinent being the editorial comment from 2010 whose title possibly says it all:
Transcranial direct current stimulation as a treatment for Parkinson’s disease—interesting, but not ready for prime time
J Neurol Neurosurg Psychiatry 2010;81:1061 doi:10.1136/jnnp.2010.205112
The editorial refers to a paper in the same issue that investigated the use of tDCS in Parkinson’s. The results are summarised in the abstract:
Twenty-five PD patients were investigated, 13 receiving tDCS and 12 sham stimulation. tDCS improved gait by some measures for a short time and improved bradykinesia in both the on and off states for longer than 3 months. Changes in UPDRS, reaction time, physical and mental well being, and self-assessed mobility did not differ between the tDCS and sham interventions.
Benninger et al persisted in their investigations of non-invasive brain stimulation; in 2011, they published on a magnetic version:
Conclusion: iTBS of the motor and prefrontal cortices appears safe and improves mood, but failed to improve motor performance and functional status in PD.
“Intermittent theta-burst transcranial magnetic stimulation for treatment of Parkinson disease”,
D.H. Benninger, MD, B.D. Berman, MD, E. Houdayer, PhD, N. Pal, D.A. Luckenbaugh, L. Schneider, S. Miranda, MD and M. Hallett, MD
Neurology February 15, 2011 vol. 76 no. 7 601-609
Which seems to indicate that the electrical version (tDCS) is slightly superior to the magnetic one.
So… I asked “How effective are these procedures?” From the evidence that I found online, the answer seems to be “a bit”. The electrical version (represented chiefly by tDCS) seems to be the frontrunner over the magnetic one (represented by TMS), and it does sound promising, although in need of some refinement. All things considered (including the following bit about what tDCS is actually like), I’d be more than happy to volunteer for a trial.
But what’s it like to have tDCS?
February 2012’s New Scientist has an article about tDCS. The author – and guinea pig – of the article (Sally Adee) has also written a blog piece about the experience – which, it seems is rather fabulous:
[…] the thing I wanted most acutely for the weeks following my experience was to go back and strap on those electrodes.
Sally Adee, “Better Living Through Electrochemistry“
Why is that, then, Sally?
I only remember feeling like I had just had an excellent cup of coffee, but without the caffeine jitters. I felt clear-headed and like myself, just sharper. Calmer. Without fear and without doubt. From there on, I just spent the time waiting for a problem to appear so that I could solve it.
Basically, Sally reports that the background “voices” of fear and doubt had disappeared – and that, clear-headed, she found herself highly capable, moreso than she could have ever dreamt.
In the New Scientist article (which seems, atypically, to be available in full at no charge), the drive behind the use of tDCS is the investigation of something called flow.
[…] that feeling of effortless concentration that characterises outstanding performance in all kinds of skills.
Flow has been maddeningly difficult to pin down, let alone harness, but a wealth of new technologies could soon allow us all to conjure up this state. The plan is to provide a short cut to virtuosity, slashing the amount of time it takes to master a new skill – be it tennis, playing the piano or marksmanship.
Despite its potentially crucial role in the development of talent, many researchers had deemed the flow state too slippery a concept to tackle – tainted as it was with mystical, meditative connotations. In the late 1970s, Csikszentmihalyi, then a psychologist at the University of Chicago, helped change that view by showing that the state could be defined and studied empirically. In one groundbreaking study, he interviewed a few hundred talented people, including athletes, artists, chess players, rock climbers and surgeons, enabling him to pin down four key features that characterise flow.
The first is an intense and focused absorption that makes you lose all sense of time. The second is what is known as autotelicity, the sense that the activity you are engaged in is rewarding for its own sake. The third is finding the “sweet spot”, a feeling that your skills are perfectly matched to the task at hand, leaving you neither frustrated nor bored. And finally, flow is characterised by automaticity, the sense that “the piano is playing itself”, for example.
I found the discussion of “flow” rather interesting. It sounds a bit like getting stuck into a painting, or some other absorbing task; usually something that I’m good at. The relationship between tDCS and talent reminds me of the suggestion that creative pursuits – one of the absorbing tasks that I, personally, can think of – can be therapeutic for Parkinson’s Disease. (You can read my blog post on the subject here.) I rather suspect that, should a Parkie manage to achieve a sense of flow in an activity, their symptoms would lessen and they would feel better about themselves.
Finally, it’s worth asking how tDCS works.
The mild electrical shock is meant to depolarise the neuronal membranes in the region, making the cells more excitable and responsive to inputs. Like many other neuroscientists working with tDCS, Weisend thinks this accelerates formation of new neural pathways during the time that someone practises a skill.
Which sounds pretty good. No new neurons – but new way of using the ones that you do have. Which makes me think of various suggestions that alternate ways of doing things are of use in coping with Parkinson’s. It’s a shame that there doesn’t seem to be any real therapeutic effect found for tDCS (yet).