Vagus nerve stimulation

VNS implantation devices consist of a titanium-encased generator about the size of a pocket watch with a lithium battery to fuel the generator, a lead wire system with electrodes, and an anchor tether to secure leads to the vagus nerve. The battery life for the pulse generator is "between 1 [and] 16 years, depending on the settings [ie how strong the signal being sent is, the length of time the device stimulates the nerve each time, and how frequently the device stimulates the nerve]."[1] The device is currently only made by Cyberonics, Inc. However, other "wearable" devices are being tested and developed by other companies that involve transcutaneous stimulation and do not require surgery. These devices are similar to TENS (Transcutaneous Electrical Nerve Stimulation) devices that are often used for pain management. The electrical impulses are targeted at the left aurical (ear), at points where branches of the vagus nerve have cutaneous representation, specifically the inner left tragus, but the meatus and concha have also been targets. To date, there have been no studies conducted on the effectiveness of such devices, though several patents have already been filed. US Patent #20070067004, #20080249594, #20090287035, #20100057154. Implantation of the Cyberonics VNS device is usually done as an out-patient procedure. The procedure goes as follows: an incision is made in the upper left chest and the generator is implanted into a little "pouch" on the left chest under the clavicle. A second incision is made in the neck, so that the surgeon can access the vagus nerve. The surgeon then wraps the leads around the left branch of the vagus nerve, and connects the electrodes to the generator. Once successfully implanted, the generator sends electric impulses to the vagus nerve at regular intervals.[2] The left vagus nerve is stimulated rather than the right because the right plays a role in cardiac function such that stimulating it could have negative cardiac effects. [3]