Electroceuticals—devices that treat ailments with electrical impulses—have a long history in medicine. Think pacemakers for the heart, cochlear implants for the ears and deep-brain stimulation for Parkinson’s disease. One of these approaches is poised to become more versatile, dramatically improving care for a host of conditions. It involves delivering signals to the vagus nerve, which sends impulses from the brain stem to most organs and back again.
New uses of vagal nerve stimulation (VNS) have become possible in part because of research by Kevin Tracey of the Feinstein Institute for Medical Research and others showing that the vagus nerve emits chemicals that help to regulate the immune system. The release of a specific neurotransmitter in the spleen, for instance, quiets immune cells involved in inflammation throughout the body. These findings indicated that VNS might be beneficial for disorders beyond ones marked by disturbed electrical signaling, such as autoimmune and inflammatory conditions. It could be a boon for patients with those conditions because existing drugs often fail or cause serious side effects. VNS may be easier to tolerate because it acts on a specific nerve, whereas drugs generally travel throughout the body, potentially disrupting tissues beyond those targeted for treatment.
So far studies of inflammation-related applications are encouraging. VNS devices developed by SetPoint Medical (co-founded by Tracey) have proved safe in early human trials for rheumatoid arthritis, which causes painful, disfiguring inflammation of joints, and for Crohn’s disease, which involves inflammation of the intestines. Additional trials for both are currently under way. The electroceutical approach is also being considered for other maladies that have an inflammatory component, such as cardiovascular disease, metabolic dysregulation and dementia, as well as for autoimmune disorders such as lupus, in which the vagal nerve itself becomes underactive. Preventing immune rejection of transplanted tissues is yet another potential application.
Most vagal nerve stimulators, including SetPoint’s devices and those already in use for treating epilepsy and depression, are implants. Physicians usually place the device under the skin below the clavicle. Wires from the implant wrap around one branch of the vagus nerve and deliver electrical impulses to it at preset intervals; the frequency and other properties are programmed via an external magnetic wand. Today’s implants measure about an inch and a half in diameter but are expected to become smaller and more finely programmable over time.
Noninvasive, handheld vagal nerve stimulators meant to ease cluster headaches and migraine have recently also gained FDA approval, although exactly how vagal nerve stimulation helps those conditions is unclear. The handheld devices deliver mild electrical stimulation to the nerve through skin on the neck or through the ear.
The vagus nerve is not the only one to be targeted by new electroceutical approaches. In late 2017 the FDA approved a nonimplanted device that eases opioid withdrawal by sending signals to branches of the cranial and occipital nerves through skin behind the ear. The device gained the FDA’s nod after 73 patients suffering from opioid withdrawal saw a 31 percent or higher reduction in symptom severity.
The cost of implants and surgery could hamper widespread adoption of VNS therapy, although that problem should ease as the technology becomes less invasive. But cost is not the only challenge. Researchers still need to know more about how VNS produces its effects in each condition and how best to determine the optimal patterns of stimulation for individual patients. It is also possible that impulses targeted at the vagus nerve may affect surrounding nerves in undesirable ways.
Nevertheless, as more studies and trials examine the mechanisms and effects, VNS and other electroceuticals may ultimately be able to better manage a wide range of chronic conditions, potentially reducing the need to take medicine for millions of patients.