VNS device implantation involves an incision made on the upper left side of the chest where the pulse generator is implanted, and another small incision made horizontally on the left side of the lower neck (where wires that connect the pulse generator to the vagus nerve)[17].

Vagus nerve stimulation (VNS) usually consists of an implantable device with a pulse generator, lead wire, and external remote components to control the device. There is a programming software which remotely controls the transcutaneous magnetic control accessory. The software can trigger a pulse or stop the stimulation in case it is painful or not working properly [18]. Stimulation of the left cervical is preferred to the right cervical because it is the side where the heart is. There could be complications or adverse effects when the right cervical is stimulated. Therefore, it is safer to stimulate the left cervical.

VNS works for focal and generalized epilepsy However, it is used more for focal epilepsy because they tend to be drug-resistant and VNS is the alternative treatment plan in that case. “In the study of Kahlow et al.,focal epilepsy represented 71 % of the 143 adult patients implanted”[18].

“The typical stimulation method involves two helical electrodes wrapped around the cervical branch of the (vagus) nerve” [15]. However, non-invasive methods are being explored to eliminate the damage caused by the treatment. Two non-invasive methods of VNS include: transcutaneous cervical VNS (tcVNS) and transcutaneous auricular VNS (taVNS). Each type of VNS causes a unique response to stimulation. The tcVNS uses a surface electrode placed on the neck (skin) to target the cervical branch of the vagus nerve which is activated by the implanted VNS (under the skin).

Recent studies found that an average seizure was reduced by “64.4% in 16 out of 17 of their patients after 6 months of treatment with tVNS” [16]. In this study, 20 min of tVNS stimulation with a 10Hz frequency was conducted 3 time a day for 6 months to the left concha. The concha is a region of the ear where there are cutaneous afferent vagus nerve distributions. Therefore, stimulation in the concha will stimulate the cutaneous afferent vagus nerve. The stimulation of the auricular branch of the vagus nerve is non-invasive and easily accessible because it is outside and is a visible part of the ear. So, stimulation of the concha is the simplest method for tVNS stimulation. Currently, the exact reason for seizure reductions with the use of taVNS is not found. Though it is successful in reducing seizures, it is not complete treatment for epilepsy. Our design plan is to conduct more experiments to solidify the success rate of taVNS. Based on the experiment procedure, it can be understood that regular stimulation of the auricular vagus nerve sets a new pace for sending electrical signals which allows the body to return to a homeostatic state.

In a study using the Hering-Breuer (HB) reflex as a biomarker for vagus nerve stimulation, it was found that tcVNS can activate the HB reflex while taVNS could not [15]. Therefore, tcVNS is more responsive to stimulation and will be better for treatment purposes. There is a visual representation of the medical devices used for non-invasive VNS.