Inserting a “pacemaker” into the brain to emit regular pulses of electricity and quell disordered neural activity may sound like a therapy of last resort, but if current experiments show beneficial results the brain surgery may one day be commonplace. But some scientists are cautioning that research on so-called deep brain stimulation may be pressing ahead too quickly, and warn that long-term effects of the surgery are not yet clear.
A growing number of psychiatric researchers are testing the method’s effectiveness on a host of psychiatric disorders. Until recently, deep brain stimulation was approved in the U.S. only to treat certain movement disorders, primarily those of Parkinson’s disease, for which it diminishes tremors and rigidity and improves mobility. To date, more than 60,000 patients worldwide have had the devices implanted [Los Angeles Times]. But now large clinical trials are in the works that will test the use of deep brain stimulation for obsessive compulsive disorder, epilepsy, and depression. Smaller experiments are beginning to assess the therapy’s effectiveness on a wide range of disorders including anorexia, drug addiction, obesity, traumatic brain injury, and Alzheimer’s.
One of the unresolved questions is exactly which brain area to target for each of these disorders, says Thomas Schlaepfer, a psychiatrist who works on deep brain stimulation. Schlaepfer says the two large clinical trials being conducted on deep brain stimulation for depression may be premature. In a trial, he says, one needs to keep the area of stimulation constant in every patient. But only about 50 depressed patients so far have been treated with deep brain stimulation, and “it’s just not enough to make an informed decision on what the right target [in the brain] is,” he says. “This research is mainly driven by industry and not by public funding, [and] it’s going a little bit too fast for my taste” [Los Angeles Times].
Deep brain stimulation has proven to be more effective than medication in the treatment of Parkinson’s, but whether it will provide striking benefits for other patients remains to be seen. In Parkinson’s, the electrodes are implanted in a part of the brain that is thought to relay movement commands to the body; the electrodes’ pulses are thought to reduce extraneous commands. But in other parts of the brain, deep brain stimulation may cause more activity, researchers say. “Right now it’s not only not known which cells are the target, but also if they turn [their activity] up or down” in response to the stimulation, says Dr. Karl Deisseroth of Stanford University. “It’s that level of confusion” [Los Angeles Times].
Related Content:
80beats: Taming Parkinson’s With Electric Pulses Through the Spine
80beats: Obsessive Compulsive Sufferers May Find Relief With a “Brain Pacemaker”
80beats: For Treating Parkinson’s, A “Brain Pacemaker” Beats Out Medication
Image: Wikimedia Commons. Electrodes are transplanted in a Parkinson’s patient.
June 1st, 2009 at 8:02 pm
Why don’t they just MRI scan the patients to see if the cells are turning up or turning down… blood flow should show that. Scan before and after.
Also, I mean, we may not know the long term effects of the treatment, but we damned sure know the long term effects of suffering with these diseases. If it’s bad enough you ask someone to drill some wires in your brain, crazy cancers or whatever else may be the least of your concern at that point.
Heck, if this therapy could get my mom off the 13 or 14 prescriptions she takes every day, I’d say send her in tomorrow – the drugs are destroying her life bit by bit, and it’s heartbreaking to watch. Cancer after ten or twenty good years of life would beat this slow downward spiral.
June 1st, 2009 at 8:51 pm
Nick, if only it were so simple!
Here are just a handful of issues to think about:
1. We have both excitatory and inhibitory neurons in our brains. When inhibitory neurons fire, they turn off other neurons (or reduce their rate of firing). So an increase in blood flow in one area does not tell us if net activity from that area goes up or down, not with the level of precision you need for the kind of experiment you envision.
2. Electrodes produce artifacts on MRI, because they are metal and conduct electricity, reducing image precision, sometimes severely, anywhere near them.
3. The magnetic field of the MRI can potentially do two things to implanted electrodes. A) they may induce a current to flow through them, which would in turn stimulate the targeted brain area in a completely uncontrolled manner. This would be bad for the person in question, or B) they may actually cause the electrode to move, possibly with considerable force, which essentially turns the electrode into a little scalpel careening through the person’s brain. This would be VERY bad for the person in question. You might get around B by making an electrode out of a non-ferromagnetic metal, but I’m not so sure that the laws of physics allow you to get around A. Your electrode has to be a conductor, or else it won’t work.
(Note that having an implanted ferromagnetic object in any soft part of your body (eg pacemaker) is a contraindication for MRI scanning. One exception is orthopedic hardware because those are fixed firmly into bones)
4. The resolution of functional MRI also isn’t quite good enough for the kind of detail you need for this kind of experiment, at least not yet.
June 1st, 2009 at 9:40 pm
Unfortunately, with any type of medical treatment, the first patients are necessarily the ones taking the greatest risks. Most of us with family members who have brain disorders would opt to wait until the “beta” version has been thoroughly tested and proven safe, but…knowing the suffering that mental illness can cause to the one with the condition and to his/her care givers as well, I can only extend the sincerest sympathy to those who find themselves needing to make this sort of choice.
June 2nd, 2009 at 8:38 am
Terminal Man!
June 2nd, 2009 at 2:28 pm
Beg to differ, MRI’s are routinely used post-op to check electrode placement, however they are specialized equipment that do not cause the fatal superheating of electrodes produced by MRI’s found in most hospitals.
Consequently on our med alert pendants we engrave “No MRI’s” subject to review by the surgical team that performed the implant.
Dr Roger Morris, Moderator
DBS Surgery, Yahoo Healh Group
June 2nd, 2009 at 11:38 pm
Dear Dr. Morris,
It is refreshing to me to read of a medical professional moderating the comment section of any forum.
All too often from my many years of reading and/or participating in any of these forum settings the dissemination of misinformation is rampant whether inadvertently or otherwise.
While I am not experienced or knowledgeable in the area of DBS, as a very long time support person, caregiver and as I refer to myself as a lay-depression expert to my spouse, I can also state the same holds true for the dissemination of misinformation as it relates to VNS Therapy (Vagus Nerve Stimulation) and the use of MRI.
The bigger issue being as you duly noted the potential to detrimentally heat the electrodes. As with VNS patients they too are capable of having MRI with precautionary information noted, proper equipment and trained medical professionals.
Once again, thanks for taking the time to share your professional knowledge in the hope that others may learn in order to also prevent alarmism and fear mongering.
Warmly,
Herb
VNSdepression.com
June 3rd, 2009 at 3:44 pm
Thanks Herb,
My degree is in psychology and I’m many years retired, but due to DBS surgery I remain a very active patient.
Roger