Epilepsy is a neurological disorder with abnormal brain activity. It causes convulsions or periods of unusual behavior, sensations, and sometimes loss of awareness. Drug-resistant epilepsy (DRE) affects an estimated 15%-20% of patients with epilepsy. Vagus nerve stimulation (VNS) is a type of neuromodulation. VNS therapy is an adjunctive neurostimulation treatment for DRE patients who are unsuitable for respective surgery or have experienced unsuccessful surgery. VNS involves the use of a device to stimulate the vagus nerve with electrical impulses. VNS is not a cure for epilepsy, and most epilepsy patients can still experience seizures or use epilepsy medication after the procedure. However, 60%-70% of patients can have over 50% reduction in seizures 5 years after the VNS procedure. Seizure intensity may also reduce. VNS is safe with tolerable side effects in most cases. The mechanism of VNS action against epilepsy is still not accurately verified. Some people believe that VNS therapy improves their mood, memory, or alertness and may also help reduce depression. VNS therapy is also expected to work in other indications, including psychiatric, gastrointestinal, endocrinological, and immunological disorders.