Vagus nerve stimulation

Vagus nerve stimulation (VNS) is an invasive medical procedure used as an adjunctive treatment for intractable epilepsy and treatment-resistant clinical depression. It is indicated for use as a last chance method, when other treatments have failed to work. VNS has been used to treat epilepsy since 1997. The depression indication was approved by the Food and Drug Administration (FDA) in 2005.

VNS uses an implant that sends tiny electric shocks to the vagus nerve. A connecting wire is run under the skin from the device to the vagus nerve in the left side of the neck. Three small leads are then carefully attached to the nerve. Implantation is usually accomplished within 1 to 2 hours. The mechanism of therapeutic action is unknown. [1][2]

The FDA's approval of VNS for treatment-resistant depression in 2005 remains controversial. According to Dr. A. John Rush, vice chairman for research in the Department of Psychiatry at UT Southwestern Medical Center at Dallas, results of the VNS pilot study showed that 40 percent of the treated patients displayed at least a 50 percent or greater improvement in their condition, according to the Hamilton Depression Rating Scale.[1] This finding does not take into account improvements over time in patients without the device. In the only randomized controlled trial VNS failed to perform any better when turned on than in otherwise similar implanted patients whose device was not turned on.[3] An investigation by the Senate Finance Committee revealed that FDA medical device chief Dr. Daniel Schultz, in his decision to approve VNS, overruled the evaluation of more than 20 FDA scientists who determined that the safety and efficacy of the device had not been demonstrated.[4]

The VNS device is made by Cyberonics Inc..