VNS: Device

• The Cyberonics NeuroCybernetic Prosthesis (NCP) Pulse Generator is an implantable, multiprogrammable, bipolar pulse generator that delivers electrical signals to the vagus nerve for the purpose of reducing the frequency of partial onset seizures. The Model 100 is shaped like a disk, 55 mm in diameter and 13.2 mm thick. (That is about the same size as a small pocket watch.) The device is housed in a hermetically sealed titanium case and is powered by a single lithium thionyl chloride battery. The battery generally lasts from 36 to 60 months. When the battery is depleted the generator has to be removed and replaced with a new one.

• The Model 100 NCP Pulse Generator is an implantable, multiprogrammable Pulse Generator that delivers electrical signals to the vagus nerve. Constant current, capacitively coupled, charge-balanced signals are transmitted from the Generator to the vagus nerve via the NCP Lead (Model 300 Series).
• The Model 100 NCP Pulse Generator is housed in a hermetically sealed titanium case. Feedthrough capacitors are used to filter electromagnetic interference from the Pulse Generator circuitry. The major components and functions of the Generator are as follows: a microprocessor, a voltage regulator, a 76.8 kHz crystal oscillator, one antenna to transmit information and another antenna to receive information, communication circuitry, DC-DC voltage generation and control circuitry, constant current control circuitry, a dual pole magnetic reed switch for manual activation of the Generator and for inhibition of the output pulses, and a lithium thionyl chloride cell to provide power for stimulation and circuit operation. The lithium thionyl chloride battery chemistry has the low impedance and high energy density characteristics required for the rapid pulsing needed in peripheral nerve stimulation, and similar batteries have been previously used in cardiac pacemakers, implantable spinal cord stimulators, and implantable drug pumps.
• The implantable lead delivers electrical signals from the Generator to the vagus nerve. The Lead has two helical electrodes with a helical anchor tether for placement around the nerve and two 5-millimeter (mm) connectors for attachment to the generator. The helix of the Lead is available in two sizes of inner diameter (2.0-mm and 3.0-mm) to allow for appropriate fit on different sized nerves. The helical design is soft, pliable, and expands or contracts with changes in nerve diameter, which may occur immediately post implant. These design features allow the 2-mm inside diameter helical electrode to fit most vagus nerves. The Model 300 NCP Bipolar Lead is insulated with silicone rubber and is bifurcated at each end. The Lead wire is quadrifilar MP-35N, and the electrode is a platinum ribbon.

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