There are two main types of vagus nerve disorders. One is caused by an under-active or inactive vagus nerve, while the other is caused by a vagus nerve that overreacts to ordinary stimuli. Patients with under-active vagus nerves often experience severe gastrointestinal problems requiring longterm treatment. Those with overactive vagus nerves may faint frequently. This condition is not considered harmful, though patients can be accidentally injured as a result of sudden fainting.
Vagus nerve disorders that stem from an under-active vagus nerve often lead to a condition known as gastroparesis. Patients suffering from this disorder may experience pain in the stomach, nausea, heartburn, stomach spasms, and weight loss. These symptoms occur because the vagus nerve is unable to direct enough blood to the stomach to complete digestion properly. In most cases, patients with gastroparesis will need to manage the condition medically for the rest of their lives.
In some patients, problems with the vagus nerve may be seen in other systems as well. This nerve is partially responsible for maintaining the heart rate and blood pressure, and if it doesn't function properly, patients may need a range of medical interventions in order to live. Pacemakers may be used to keep the heart rate from dropping and medication may be needed to increase the blood pressure to within an acceptable range. Vagus nerve disorders that are this severe are rare and often either congenital or the result of a serious illness or injury to the nerve.
Patients may also suffer from vagus nerve issues that are caused by an overactive vagus nerve. The main symptom of these disorders is fainting. In most cases, patients who have overactive vagus nerves will begin fainting at the onset of puberty. Once doctors have determined that the vagus nerve is responsible for the fainting, no further medical intervention is needed. Though it is possible for patients to injure themselves in a fall, there is no risk from the activity of the vagus nerve itself.
Overactive vagus nerve disorders can be triggered by a number of different causes. The vagus nerve diverts blood to the stomach and may divert too much away from the brain when a patient is vomiting, digesting a large meal, or having a bowel movement. Stress and emotional stimuli can also cause the vagus nerve to divert too much blood away from the brain.