Deep brain stimulation

Professor Helen Mayberg describes the dramatic changes observed in depressed patients treated with deep brain stimulation, discussing how this has impacted how we view the brain and treatment.

Deep brain stimulation is a technology that was really developed for treating movement disorder. It is the implantation of small wires that can deliver very focal stimulation to a particular area in the brain, and can do it continuously using an implanted battery pack, just like a pacemaker. So while we don’t classify it as a brain pacemaker, it in essence is. By knowing a circuit in the brain that we believe is dysfunctional, by having a particular node in the circuit board that we think is at the center of the problem, we can implant, very precisely, a device that can modulate that circuit on demand. We piloted this hypothesis, now going back about 5 years, in a group of patients who had depression that could just not be treated. They had failed multiple drugs, failed therapy, failed electroconvulsive shock therapy. Pretty much, they were trapped and enslaved by their brain with no chance to be better or not. These people didn’t work, they didn’t leave their house, basically all they could think about was how can I ever be any other way than I am now, this is absolute purgatory. Because of what we believed we knew from our other experiments, we felt as though in this circuit there was an offending node in the brain, that if we could modulate its activity very directly that we could change the state of the network and perhaps help these patients. We used the technology that had been well established in Parkinson’s [disease] and we applied it to the network model that we had for depression. We piloted this and much to our delight, the patients came out of their depression. Not only does it hold with chronically stimulating or modulating or pacing this system over time, but actually we could watch patients lift out of the depression in the operating room on the table, because they were awake when we did the implantation. So it also taught us something about the way in which this network functions. We’ve always thought about depression and the treatment of depression as taking a very long time, that there need to be plastic changes in the brain, the chemistry needs to change and that that process takes many weeks. What we saw in the operating room was that part of this pervasive state could actually change immediately. Not that they were well, but that the part of the pervasive psychic pain, that block, that heaviness, that ‘just can’t get outside myself to pay attention to anybody else because I’m getting this terrible negative signal’, that suddenly just stopped immediately when we stimulated one of the four contacts, and we’ve been trying to study which is the absolute most precise contact that’s best for each person. It’s as if you suddenly are back to a state where other things are possible, but that there’s something wrong with the network in these patients because you then pace them over a long period of time, and if you turn it off over several weeks their depression will come back. But if the stimulation stays on, and we have patients that are now out five years, they are well; they haven’t relapsed. So we’ve done something fundamental to this circuit. We’ve allowed it to go back to functioning much more normally, so it isn’t just that we got them out of their depression, we’re keeping them from going back to a depressed state. One of the things about depression is, usually no matter what you do, people’s illness will return. So, we are on to something that’s teaching us something much more fundamental about the nature of this circuit and what may be wrong with it in different groups of depressed patients that I think will lead to new advances in what’s special about that chemistry – why that brain area? How can you apply small amounts of current all the time and not have side effects? Why does it keep the depression from coming back? What does that mean about the rhythms of the brain? Suddenly, an experiment that just should have worked based on our imaging has opened up a whole avenue of research about the nature of emotional circuits in the brain and how they work.