Professor Helen Mayberg discusses how deep brain stimulation (DBS) is applied to the subcallosal cingulate, a structure deep in the brain's white matter.

To do the procedure, the patients are first fitted with a frame that allows the surgeon to both take a picture of very high resolution MRI, structural picture of the brain, so in fact one can see precisely in 3 dimension where one wants to place this very, very small wire. We are talking about placing a wire that’s a centimeter long and a millimeter wide; that’s the active area of the electrode and it’s attached to a long wire. So we want to implant it and it turns out where we want to implant it is very deep in the brain, so we need a guidance system to get there. That guidance system is called a stereotactic frame. So the frame is attached to the skull, the patient is put into an MRI scanner and a 3 dimensional picture of the brain is taken. The patient is then taken to the operating room, is placed on a bed and is attached in their frame to the frame of the operating room table. That becomes a conduit for us to look at a computer and know exactly where that patient’s brain is relative to that frame, and actually to plan in 3 dimensional space where that wire will be placed in the brain. The way it’s placed is that a small hole needs to be made in the skull because this wire is placed inside the brain; this is not done externally, isn’t done in the neck, it’s actually implanted in the brain itself. So about the size of a quarter at biggest, a burr hole, a small opening in the skull is made with a special drill under local anesthesia so the patient doesn’t feel anything because their scalp and their skull is numbed up with medication, but they are awake in the operating room. Two holes (one on each side) are placed right off the center line of the skull, and then a guide wire is placed and we can actually listen to the cells in the brain as we watch the MRI and know precisely where the position of the wire is as it’s advanced slowly through the substance of the brain, deep into our target, which is the subcallosal cingulate. It’s around an area of the brain in the anatomy book that’s called brodmann area 25, so for short hand we call it area 25, but it is actually the subcallosal cingulate white matter; we can see it on the MRI. We can then guide with the stereotactic frame and the coordinates precisely to put the tip of the electrode, which contains the active contacts, at that precise spot (one on each side). Once it’s in place, the wire comes up through the rest of the brain, comes out through the little hole in the top of the skull, we can hook it up to a pulse generator and we can tune in what amount of current with any parameter we want and direct the current precisely to one of the four contacts that’s implanted. Then we can systematically test what happens when you stimulate contact 1, which is separated by contact 2 by a millimeter and a half and actually test at different frequencies, at different currents, what happens when you stimulated each one of those targets? Now we pick that target because that is an area that needs to turn down its activity in our various other experiments with other treatments. That area turns out to be overactive in these intractably ill patients who haven’t responded [to other treatments]. We can define that white matter, because if we stimulate in those white matter tracts right next to area 25, we will not only affect area 25’s activity locally, but we will get current affecting everywhere along the white matter cable that goes to the frontal lobe, that goes to the hypothalamus, that goes to the amygdala. Because we’ve mapped out the entire circuit that’s important for depression, turns out that area 25 in this particular track is centered in a location where if you stimulate there, you affect the entire network, and so that’s how we do it and once we test it and make sure there’s not any problems, we secure the wire at the skull, the wire is attached to a small cable that then can be tunneled under the skin, under the scalp, under the neck and everything can be put inside the body; nothing is exposed to the outside, and that the end of the connector cable is then attached to a battery that goes in the chest just like a pacemaker for a heart pacemaker. We can actually control the current to the electrodes in the brain by putting a little magnetic paddle on the outside of the skin and tuning any of those four contacts on either side of the brain (so 8 total contacts) with a little battery on the outside of the skin there. Once the electrodes are secured and we’ve tested, the patient is taken out of the frame, they are put to sleep and this part of the procedure is done under general anesthesia. This takes a good part of the day because we do testing in the operating room; at it’s fastest we could do it in about four hours and it takes about an hour to implant the final battery. Patients wake up in about 20 - 30 minutes. They tolerate the procedure incredibly well, and generally can go home the next day or the day after, and then we go through a process of testing and tuning and determining which is the optimal contact. We’re finding that our imaging is probably the best way to determine which is the optimal contact, and now we’re getting much fancier by trying to define what are the networks that we can see with our imaging so that we know precisely in advance which is the best contact and then we’re testing that experimentally.

deep brain stimulation, dbs, subcallosal cingulate, depression, treatment, helen, mayberg