The vagus nerve is the main nerve of the parasympathetic autonomic nervous system. Beyond its vegetative functions, the vagus nerve possesses anti-inflammatory and
analgesic properties. Initially developed in the treatment of
refractory epilepsy,
vagus nerve stimulation (VNS) is currently being evaluated in several
musculoskeletal diseases. VNS can be invasive by placing an
electrode around the cervical vagus nerve and connected to a generator implanted subcutaneously or non-invasive stimulating the cervical vagus nerve branch percutaneously (auricular or cervical). In
rheumatoid arthritis (RA) patients, VNS has been shown to dampen the inflammatory response of circulatory peripheral cells. Several open-labeled small pilot studies have demonstrated that VNS, either invasive or transcutaneous, is associated with a significant decrease of RA disease activity. As well, other studies have shown that VNS could limit
fatigue in
Sjogren's syndrome and systemic lupus, or decrease
pain in
fibromyalgia as well as in erosive hand
osteoarthritis. However, some questions remain, such as the settings of stimulation, the
duration of treatment, or the optimal stimulation route. Finally, randomized controlled trials versus
sham stimulation with large samples of patients are mandatory to definitively conclude about the efficacy of VNS.