About Vagus Nerve Stimulation Therapy

I wrote The Patient's Guide to Vagus Nerve Stimulation and Depression as a patient (who has been implanted with the device) for patients, to help you make an informed decision about the implant procedure.

A VNS Therapy^TM web site would be incomplete without the details of the vagus nerve stimulator implant procedure. This article will sound very intricate and will unfairly cloud the procedure as a dangerous operation. Further complicating the issue is that the medical community is not familiar with the vagus nerve stimulator. However, it is important to note that medical device chest implants have been done safely for decades. This exact operation has been safely done on over 27,000 epilepsy patients.

You need to rely upon the experts (neurosurgeons) to assess the risk of implanting the vagus nerve stimulator.

The VNS Therapy^TM System ("VNS Therapy System") includes the following:

• A generator to provide the appropriate stimulation to the vagus nerve;
• A lead that is attached to both the generator and the vagus nerve;
• Associated equipment to assist with necessary implantation surgery;
• Equipment to assist with setting the stimulation parameters particular to the patient;
• Appropriate instruction manuals; and
• Magnets to suspend or induce stimulation manually

The implantation of the generator and lead into patients is generally performed on an outpatient basis. The battery contained in this generator has a finite life, which varies according to the model, the stimulation parameters and settings used for each patient. At or near the end of the useful life of a battery, a patient may, with the advice of a physician, choose to implant a new generator, with or without replacing the original lead.

Source: Cyberonics, Inc.

Pulse Generator. The pulse generator is an implantable, programmable signal generator designed to be coupled with the bipolar lead to deliver electrical signals to the vagus nerve. The pulse generator is a battery powered device. Shortly before or upon depletion of the battery, the pulse generator may be removed and a new generator implanted in a short, outpatient procedure.

The Model 102, 102R, DemiPulse^TM and DemiPulse^TM Duo VNS Therapy pulse generators, the only pulse generators we currently offer in the U.S., are similar in design and manufacture to a cardiac pacemaker. The generators are comprised of one printed circuit board and a battery hermetically sealed in a titanium case. Standard components are assembled on printed circuit boards using surface-mount technology. The assembled circuit boards are then tested and mounted with the battery in the titanium case, which is laser welded. A header to which the bipolar lead connects is added and each unit is subject to final release testing prior to being sterilized.

Bipolar Lead. The bipolar lead conveys the electrical signal from the pulse generator to the vagus nerve. The lead incorporates electrodes, which are self-sizing and flexible, minimizing mechanical trauma to the nerve and allowing body fluid interchange within the nerve structure. The lead’s two electrodes and anchor tether wrap around the vagus nerve and the connector end is tunneled subcutaneously to the chest where it attaches to the pulse generator. The leads are available in two sizes of inner spiral diameter to ensure optimal electrode placement on different size nerves.

Programming Wand and Software. Our programming wand and proprietary software are used to interrogate the device and to transmit programming information from a handheld computer to the pulse generator via electromagnetic signals. Programming capabilities include modification of the pulse generator’s programmable parameters (pulse width, amplitude, frequency and ON and OFF intervals) and storage and retrieval of telemetry data.

Tunneling Tool. The tunneling tool is a single use, sterile, disposable surgical tool designed to be used during surgical placement of the bipolar lead. The tool is used for subcutaneous tunneling of the lead assembly between the nerve site in the neck and the pulse generator site in the chest.

Accessory Pack. The accessory pack includes two resistor assemblies used to test the function of the device prior to implantation, the bipolar lead tie-downs and one hex screwdriver.

Source: Cyberonics Inc., 10-K, filed 6/24/2008