Medtronic: Overtightening screw can damage wire that delivers therapy to brain

  • Article by: JAMES WALSH , Star Tribune
  • Updated: May 7, 2013 - 5:14 PM

Two surgeons agree with manufacturer that damage to a deep brain stimulation device wouldn’t be life-threatening.

A deep brain stimulation device used to treat conditions like Parkinson’s disease was classified Thursday by the U.S. Food and Drug Administration as a Class I recall — meaning the FDA believes there is a “reasonable probability” that a device will cause “serious adverse health consequences or death.”

But on Friday, Medtronic and two doctors said they were baffled by the seriousness of the FDA recall, noting that patients are not in imminent danger. “No one’s going to die,”said Dr. Bryan Klassen, a Mayo Clinic neurologist who specializes in movement disorders and Parkinson’s.

Said Dr. Ali Rezai, a neurosurgeon and director of neuromodulation at Ohio State University: “It’s definitely not life-threatening. That is really incorrect. … I was very surprised by this.”

FDA officials on Friday did not respond to a request for an explanation about the recall classification. On Tuesday, an FDA spokesperson sent an e-mail to the Star Tribune, saying: “In making this risk-based assessment, the agency may consider factors about which local practitioners are unaware.” The agency did not elaborate on what those factors may have been.

Deep brain stimulation is used to treat symptoms of Parkinson’s and other conditions. It connects a pacemaker-like device to the brain with wires, called leads, and sends electrical pulses into the brain to ease tremors and relax muscles. Doctors implant the device in two phases. In the first phase, the leads are connected to areas of the brain to be treated. In the second phase, often a week or two later, those wires are connected to the pulse generator that sends the electrical signal.

Medtronic includes something called a “lead cap” that some doctors use to cover and protect the end of the wire that extends from the brain until it is connected to the generator, said Justin Ihle, a Medtronic spokesman. The lead cap is affixed to the end of the wire by turning a small screw. The problem is, Medtronic discovered that overtightening the screw or twisting the lead cap can damage the lead — and possibly affect the therapy a patient receives. Medtronic alerted doctors to the problem in February and sent them a revised list of instructions for fastening the lead cap.

Ihle said Medtronic has proposed a manufacturing change to fix the problem. That is under FDA review. He said it is difficult to determine how many leads may have been damaged with the lead cap, since not all doctors who use the device use the lead cap and not all leads would have been damaged.

In fact, Ihle said, Medtronic so far has found that only about 0.25 percent of the deep brain stimulation leads it has distributed have been found to be damaged.

Rezai said he has been doing the procedure for 16 years. He never uses the lead cap, he said. Few other neurosurgeons do. Only when the lead cap is used can there be damage, he said.

If wires have been damaged, the likely result is that the patient is not receiving the full extent of the therapy. Klassen said doctors also would likely discover that at the time of the second surgery to connect the wire to the generator.

That, in itself, would not harm a patient, he said. Whereas a failure to deliver therapy for cardiac arrest from a defibrillator can be fatal, failure to deliver this therapy would mainly result in a patient’s symptoms returning. Damaged wires may need to be replaced and Klassen said there might be a heightened risk to patients needing surgery to remove damaged leads.

Medtronic said that if patients receive therapy as expected after the device is implanted, they aren’t likely to be affected. No one, Ihle said, has been reported to be harmed as a result of the problem.

Why, then, did the FDA ­classify this as a Class I recall? “We certainly can’t speak on behalf of the FDA, or their reasoning behind the classification,” he said.

Medtronic is still shipping the product, but for scheduled procedures only.

Ihle would not say how many patients have been implanted with Medtronic deep brain stimulation devices. Nor would he provide sales figures. Deep brain stimulation is part of Medtronic’s neuromodulation business, which includes spinal cord stimulation for the treatment of chronic pain and other treatments. In February, Medtronic reported fiscal third-quarter neuromodulation revenue of $447 million, 7 percent higher than the same quarter the year before.

Fiscal second-quarter neuromodulation revenue was $454 million, a 10 percent increase over the previous year, and fiscal first-quarter neuromodulation revenue of $419 million was 8 percent higher than the first quarter a year before, according to Medtronic reports.

Piper Jaffray & Co. senior analyst Thom Gunderson on Friday called neuromodulation “a nice strong business” for Medtronic, but that spinal cord stimulation for pain management makes up a bigger share than deep brain stimulation. Gunderson was asked if the recall is a wrench in the spokes for Medtronic’s neurostimulation business.

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