By Martha Nance, M.D., Struthers Parkinson’s Center
We learned late last week of a recall on the Medtronic deep brain stimulator devices that are used for Parkinson’s disease. Although the recall has been classified by the FDA as a Level 1 recall, meaning that the device could cause “serious adverse health consequences or death”, the surgeons and neurologists who use the devices are confident that our patients are not at any substantial risk of harm.
The problem that was identified has to do with a temporary cap that is used by some surgeons at the time that the stimulator devices are implanted in the brain. Most neurosurgeons place the leads into the brain (the subthalamic nucleus or the globus pallidus) during one procedure. Then, in a second procedure a couple of weeks later, they place the impulse generator, or battery, under the collarbone and connect the brain leads to the battery by means of some flexible wires tunneled under the skin. At the time of the first procedure, the surgeons often place a temporary cap under the skin over the top of the leads, which is removed when the device is connected to the battery during the second procedure.
The cap is fixed in place by a small set screw. If the set screw is tightened too forcefully, it can damage one of the leads within the device. Neither the surgeon nor the patient would be aware of that at the time, because the device is not connected to a battery yet and is not turned on. When the battery is connected to the leads a couple of weeks later, it would be immediately obvious even in the operating room, and certainly at the time of initial programming, if one of the leads was damaged, because the electrical properties of that lead (the impedance) would not be in the expected range.
The DBS device has four leads, and the one that is most likely to be impacted by an over tightening of the screw is the shallowest lead, which is often not used in programming anyway (think of the subthalamic nucleus as a baseball and the DBS electrode as a bat; ordinarily, the middle two of the four contact points would most likely represent the “sweet spot” for stimulation, just as the batter would prefer to hit the ball in the middle with the middle of the bat rather than either end!) If a particular lead is damaged, one would either make a note not to use that lead for programming, or replace the device. Replacing the device obviously carries with it the risk of an additional surgical procedure.
Some surgeons do not use the cap in the first place; like wearing a hat when you go outside in early May, it is an optional thing, not necessary for the proper placement of the DBS device. Many surgeons have used the caps successfully, without over tightening the screw. The cap itself is not dangerous, and does not remain in the body after the brain leads are connected to the battery. One report that I read indicated that 0.25 percent (1 out of every 400) of the DBS devices implanted are affected by this problem, which means that 99.75 percent of people who have had DBS devices implanted are not having a problem related to this recall.
I am trying to be as reassuring as possible to anyone who has had a DBS device implanted, without making light of a problem viewed by the FDA as serious. At Struthers Parkinson’s Center, we will work closely with Medtronic in the coming days to ensure that patients are notified of the recall, that we review our records for any evidence of DBS leads that were nonfunctional at the time of initial programming, and that any of our patients who have concerns are able to speak with the doctor or nurse, or to be seen, if necessary, in a timely fashion.
People with Parkinson’s disease should feel free to contact their treating physician or clinic with any concerns. Please do not worry unhelpfully about this issue without contacting someone about your concerns. And for those who are anticipating DBS surgery in the future, do not worry about the safety of the procedure; surgeons have been instructed not to over tighten the screw, and Medtronic is working on a more fool-proof solution to this problem.
I do not receive any personal financial compensation of any type from Medtronic; the opinions expressed in the blog are my own and do not represent an official statement from Medtronic, Park Nicollet Health Services, or Struthers Parkinson’s Center.