Worst best, best awful, best worst…the point is that Deep Brain Stimulation (DBS) is the best that we have but it isn’t that great. There are many reasons why DBS is not the panacea for brain disorders–I only picked four. If you don’t already know what DBS is you can probably figure it out from the name…neurophysiologists and neurosurgeons take a wire, hook it up to a battery, and stick it into a dysfunctional region of a patient’s brain. It is surprisingly barbaric, though measurably more humane than its parent method, electroshock therapy–which is only a hop, skip, and a jump away from death by electric chair. The main problem with this type of criticism is that, in spite of whatever ethical breaches have led to the discovery of DBS as a therapy, it seems to work.
DBS has been used with meaningful success to treat a variety of conditions with some of the most notable including Parkinson’s disease, types of Dystonia and other special neuromuscular disorders, Epilepsy, and even severe depression. DBS stimulators are typically implanted in the chest (similar to a cardiac pacemaker) with a wire electrode fed up the neck, through the base of the skull, and directly into the focal point of the dysfunctioning tissue.
Such a simple device that can and does work wonders can’t be without its flaws.
Some Of The Serious Problems
Brain tissue is more like paste than the spongy, sort of bouncy looking thing you see floating in formaldehyde–aside from neurons there are billions of other cells too. Supportive cells called glial cells are there for structure and to play several support functions; but there are also loads of immune system cells there to protect against infection and disease. When any foreign object is stuck into the brain these cells all congregate around it and stick to it in layers…this insulates the object from the vulnerable neurons in the area. Stimulating electrodes have a really short effective life in the brain because of the gunk that the body throws at them. Not only do the DBS devices stop working so well but this means that a DBS patient has to go under the knife every six-twelve months to have the electrode replaced.
2. Unintended Side-effects
With the current technology, it is impossible to activate a few neurons without also stimulating other neurons nearby. This makes sense…If you are hit by lightning and you are holding hands with your buddy, your buddy is hit by lightning too. Well, those other neurons are connected to other circuits that do other things…things you didn’t intend to do. Just to leave you with no excuses for getting my meaning, it just so happens that a strip of your brain that is responsible for helping you make sense of what you see is right next to a strip of your brain that is responsible for helping you coordinate your movements…if I were to electrically shock the one in an attempt to get you to see something, I could be unintentionally shocking the other, perhaps causing you to move spasmodically. It turns out that many brain circuits are interconnected and share real world functionality…this is especially true in the neocortex, where your decision making centers associate with your emotion centers, your sensory regions, as well as your motor regions.
Anyone who has seen The Green Mile, or been talked into licking a nine volt battery knows that electricity burns. What you might not know is that it is enormously easy to kill a few cells with a little bit of electricity. You might be thinking, “a few cells…no big deal.” Stop and consider the fact that once you reach a few years old, most of your brain has already stopped making new cells. Add to that an understanding that for most patients DBS is constantly delivering electrical current to the brain. While scientists have a pretty good idea of how strong of a shock it takes to kill a neuron quickly, they don’t have as clear of an idea what might kill neurons slowly. With the presumed safe usage of DBS already posing some potential risks to the patient, let’s not imagine what could happen if a surgeon slips up on the settings.
4. One-Size Fits All
The title of this section is a little bit misleading…the physical size of the device isn’t really a concern anymore…they have shrunk considerably since the devices first arrived in the clinic. It has more to do with the “Unintended Side-effects” problem than anything. It turns out that we don’t do a very good job of diagnosing brain disorders. Even the ones we have studied for years like Alzheimer’s have several different stages, degrees, and forms that call into question the wisdom of using a single type of therapy that is pre-programmed to deliver an out of the box protocol. While it is intuitive to calibrate the device to the needs of an individual patient’s condition, there is little to no understanding of what is optimal. It is typical that the surgeon is instructed to root around and “turn-up” the stimulation until the pathological tissue behaves more “normally”. With the special set of conditions every patient presents, it is unlikely that this degree of customization is enough.
But, Deep Brain Stimulation Is Still The Best We Have
Despite these looming concerns, DBS does amazing things for those who have no other recourse. The internet is full of testimonies of the increased quality of life that DBS brings…many couldn’t control their tremors or seizures long enough to even look where they wanted to. Walking, writing, feeding yourself, or speaking…are all activities that we take for granted but are restored (albeit temporarily and possibly at a cost) to those who are lucky enough to qualify for a DBS device. You might expect the best therapy to be a little less awful than what I have described. As worst as it is, it is still the best–and for many, it is the only cure working and we can’t take that away, even if it is just a placeholder for something better.
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Clayton S. Bingham is a Biomedical Engineer working at the Center for Neural Engineering at University of Southern California. Under the direction of Drs. Theodore Berger and Dong Song, Clayton builds large-scale computational models of neurological systems. Currently, the emphasis is on the modeling of Hippocampal tissue in response to electrical stimulation with the goal of optimizing the placement of stimulating electrodes in regions of the brain that are dysfunctional. These therapies can be used for a broad range of pathologies including Alzheimer’s, various motor disorders, depression, and Epilepsy.
If you would like to hear more about the work done by Clayton, and his colleagues, in the USC Center for Neural Engineering he can be reached at: csbingha-at-usc-dot-edu.