Auricular Vagus Nerve Stimulation (auriStim) Against Alcohol-craving Measured by Pupillary Reaction - Pilotstudy

The chronic consumption of alcohol leads to a pathophysiological adaptation of the nervous system, by an increase in glutamatergic receptors and a decrease in GABAergic receptor functions. Autonomic and psychomotor hyperactive disorders, such as nausea, tremor, diaphoresis, hypersensitive reflexes, hypertension, and tachycardia, as well as negative emotional states, characterized by restlessness, anxiety, dysphoria, and irritability occur 6 to 24 hours after cessation of alcohol consumption. The cause of the vegetative symptoms is a sympathetic driven misbalance of the autonomous nervous system. The negative state of health can last for a very long time and is the main reason for relapses.

Pharmacological treatment of alcohol withdrawal syndrome consists of ether Benzodiazepines or GHB is an endogenous metabolite of γ-aminobutyric acid (GABA).

The rate of successful treatment is lowest for alcohol dependence among all psychiatric disorders. Therefore, it seems important to carry out further interdisciplinary investigations in the direction of new and effective treatment methods. To restore vegetative balance in alcohol-withdrawal syndrome novel neuromodulatory approaches, such percutaneous auricular vagal stimulation (pVNS) could be beneficial.

The pupil size changes, like other physiological markers, e.g., hyperventilation, blood pressure and heart rate, serves as psychophysiological marker of the autonomic nervous system (ANS). Beside the fact that pupil size is determined by balance between the parasympathetic ANS (PANS) and the sympathetic ANS (SANS), measuring the static and dynamic pupillary diameters are suitable parameters measuring imbalances or dysfunction of the vegetative regulation. The pupil diameter oscillates spontaneously at low frequencies, which is an almost constant oscillatory change in the pupil size. Like pupil size, it is generally assumed that pupil oscillation is regulated by a dynamic interaction between parasympathetic (cholinergic) and sympathetic (noradrenergic) activity.

In this study, the investigator assessed the pupil reaction to the cholinergic antagonist tropicamide in alcohol withdrawal syndrome as a biomarker of the vegetative balance before and after pVNS. The Investigator hypothesized that pVNS will enhance the parasympathomimetic tone represented by a reduction of pupillary diameter in a parasympatholytic pharmacological challenge with tropicamide after vagal stimulation.