Transcutaneous vagus nerve stimulation (t-VNS) is used to treat drug-resistant epilepsy and depression. It involves activating a branch of the vagus nerve through the skin in the pinna area with electrical impulses, without the need for surgery.
What is transcutaneous vagus nerve stimulation?
Transcutaneous vagus nerve stimulation is an alternative to conventional VNS that involves surgery in the chest area. It involves implantation of a pacemaker-like stimulation device that connects to the vagus nerve via an electrode. The stimulation device is connected to the ear electrode by a thin cable. It periodically sends electrical impulses to the brain, which then releases anticonvulsant and antidepressant agents. The device signals are usually emitted every five minutes for 30 seconds each. When the pacemaker device battery is depleted, it must be replaced in a repeat neurosurgical procedure. This method has reduced the frequency of epileptic seizures by three quarters in over two years of use. However, side effects such as coughing, hoarseness and voice disorders (dysphonia) occur. They are noticeable when the device is working, but subside over time. The not insignificant side effects are due to the stimuli to which the efferent nerve fibers leading to the internal organs are exposed. Various studies have shown that patients tolerate transcutaneous VNS well, that it fits relatively smoothly into their daily lives, and that it contributes to an improved general life situation. However, it has not yet reached the therapeutic effectiveness of invasive VNS. For use, t-VNS can be used for all forms and severities of the impairments to be treated.
Function, effect, and goals
The vagus nerve is one of twelve cranial nerves and drives internal organs such as the heart and lungs, as well as the digestive tract. It has an exceptionally large distribution area in the human body, to which it ultimately owes its name. The Latin word vagari means to roam in German. The impulse-giving apparatus for the vagus nerve is about the size of a smartphone. Through a special ear electrode worn like a small pair of headphones, electrical stimuli are transmitted through the skin to the ramus auricularis nervi vagi (vagus nerve branch RANV). This branch can excite the vagus nerve and thus transmit signals via the brainstem to the upper areas of the brain, which are thought to have a seizure-reducing effect. A test showed that around 23 out of 100 epilepsy patients suffered fewer seizures in this way. In individual test subjects, the epileptic seizures even disappeared completely. Each patient can use such a device to carry out the therapy himself once a day in any location. The strength of the electrical stimulation can be regulated. Usually, a slight tingling or pulsating sensation is felt at the site of application of the device. Remarkable successes have also been achieved with this technique against severe migraine attacks. Initial practical studies also indicate healing potential for anxiety disorders, Alzheimer’s disease and unilateral headaches. In another method of non-invasive transcutaneous vagus nerve stimulation, an electric field is established at the level of the carotid artery. By applying a device about the size of a hand, the vagus nerve can then be stimulated for two minutes. This method is already allowed in Europe for the treatment of anxiety disorders, depression, epilepsy and primary headaches. Test experiments with functional magnetic resonance imaging have led to the proof that by means of transcutaneous vagus nerve stimulation exactly those brain areas are addressed as with a surgical procedure. Both methods act on a specific nerve bundle in the brainstem that plays an essential role in the development and frequency of epileptic seizures. About one-third of all epilepsy patients do not experience any improvement in their condition when given anticonvulsant (convulsant) medication. This situation has not changed significantly in recent years despite multiple changes in agents and research. For pharmacoresistant patients, stimulant procedures are therefore gaining in importance.Their risks are considered very low, especially compared to surgical procedures in which part of the brain tissue is removed to attenuate the epileptic seizures. Implanting electrodes in the brain is also a relatively risky procedure.
Risks, side effects, and dangers
Unlike invasive, transcutaneous vagus nerve stimulation does not involve unwanted irritation of nerve fibers. Thus, side effects such as hoarseness or temporary shortness of breath are also eliminated. Only during stimulation can an itching or slight pain occur in the area of the auricle, but this can be minimized or eliminated completely by reducing the intensity of the electrical stimulation. When the stimulation intensity of his device is optimally set, the patient feels at most only a slight tingling sensation in the ear. The sensible daily workload for stimulating the vagus nerve is four hours, which can also be spread out over the day. The strength of the electrical stimuli can be changed by the owner of the stimulation device at any time, so that it always best suits his own sense of well-being. From the display of the device, the patient regularly receives all the important information about the effectiveness and duration of the therapeutic measures. All data is continuously stored in the device so that the attending physician can follow the course of therapy at any time and effectively influence it. Discontinuation of the measure is possible at any time. Even in children suffering from epileptic seizures, t-VNS treatment can be performed in combination with medication.
