After an inspection of the manufacturing facility in Texas, the FDA recently notified Cyberonics there were problems with their production of vagus nerve stimulators (VNS). They raised concerns about the methods, the facilities and or controls used for their manufacturing, packing, storage, or installation stating, “in that the methods used in, or the facilities or controls used for their manufacturing, packing, storage, or installation are not in conformance with the Current Good Manufacturing Practice (CGMP) requirements of the Quality System (QS) Regulation for medical devices, as specified in Title 21, Code of Federal Regulation (CFR). Part 820.”

It is difficult to assess the seriousness of this notification. The issues raised by the FDA could reflect failure on the part of Cyberonics to provide complete documentation and investigation of potential or definite problems with the vagus nerve stimulator. In other words, the VNS implanted does not work properly in everyone due to technical problems with the leads, unexpected short battery life, or other problems. It is therefore important to investigate and document the causes of why the implantation was unsuccessful.

One main concern cited in the warning letter by the FDA was the fact that Cyberonics did not account for how and why the vagus nerve stimulator failed to continue working or was replaced. Questions raised by the FDA included, but were not limited to, issues pertaining to the VNS battery. If the VNS device required reimplantation -- is it a) that the battery is near the end of its life (and if so, based on the usage and program settings, should it be near the end of its life?), b) the battery did run out (and if so, did it run out too quickly?), c) were wires or their contacts broken?, or d) was the impedance (a measure of the total opposition to current flow) too high?

The FDA is concerned that among the thousands of patients who have been reimplanted with the VNS, that there is insufficient documentation regarding battery usage including programming history, which is defined as how long the battery lasted in relation to the amount of use. Furthermore, cases of high lead impedance have been demonstrated and the FDA is concerned that Cyberonics has not done more to define the cause in all cases, and when the cause was identified, to work to reduce the problem.

Although a recent press release was issued, we look forward to hearing Cyberonics’ complete and in-depth response to this letter. They have promised to work in a timely manner to address all of these issues. It would be helpful to patients and professionals to know more about the reasons the devices stop working and the timing of their "end of service" relative to their programming history and use. There is also the concern that some surgeons may be less technically skilled in implanting the devices that lead to great wire or contact breaks, high impedances, or even failure to directly stimulate the vagus nerve itself. There can also be considerable variability in the cosmetic results.

The FDA letter concerns only the issues related to manufacture, packing, storage, installation, and length of service. However, all of these issues and those related to its safety and effectiveness are all critical to people with epilepsy who receive, or are considering, this treatment. More data will be very helpful.

For more information regarding Cyberonics please go to:

• cyberonics.com