Vagal stimulation has been shown to reduce the prevalence of seizures in patients with epilepsy and abort migraine attacks, but until recently this has involved an operation with a significant risk of side effects. In the last few years, scientists have tested a non invasive hand-held device to stimulate the vagus nerve. Results look promising. Not only is this useful for reducing headaches and seizures, but it can also reduce other functional or unexplained symptoms. The symptoms of IBS are frequently associated with multimorbidity, headaches, tiredness, somatic pain, indigestion and many other unexplained symptoms are common in IBS. So it is likely that self administered vagal stimulation may allow people to alleviate their own IBS symptoms.
Stimulation of the vagus nerve has many effects on the body; it slows heart rate, stimulates digestive secretions and motility and reduces blood pressure, but 80% of the fibres of the vagus nerve travel from the body to the brain, where they transmit a never-ending stream of information about the state of the viscera, reduce activity in the sympathetic nervous system, and have a calming effect on the emotions. There are other ways of stimulating the vagus nerve, though these may not be so reliable. They include breathing out (pranayama) during the practice of yoga and also mindful meditation. It is through stimulation of the vagus that meals can make you feel calm and sleepy. Some probiotics are through to have a calming effect through stimulating the afferent vagal terminals in the gut.
Commercially available hand-held stimulators are specially configured so that they stimulate the afferent vagus to the brain rather than the efferent vagus from the brain to the body. They do not slow the heart rate directly nor stimulate acid secretion or gut motility. Early results indicate that non invasive vagal nerve stimulation improves the quality of life of patients with multiple unexplained bodily symptoms including headache and reduces health care costs. Trials are currently underway to investigate the effects on IBS specifically either through a device held over the vagus nerve in the neck or by a ear clip that stimulates the auricular vagal nerve terminal.