Vagus nerve stimulation (VNS) devices deliver controlled electrical impulses to the vagus nerve, modulating its activity to treat specific medical conditions. What began as an implantable epilepsy treatment in the 1990s has expanded into a diverse device landscape spanning implantable, non-invasive, and experimental platforms. This guide covers every major category of VNS device, what each is approved for, and how the technology actually works.
Implantable VNS: The Original Platform
Implantable VNS was the first form of vagus nerve stimulation to reach clinical use. The system consists of a pulse generator (similar in size to a cardiac pacemaker) implanted under the skin of the left chest, connected via a lead wire to the left cervical vagus nerve in the neck. The generator delivers intermittent electrical pulses — typically 30 seconds on, 5 minutes off — throughout the day.
LivaNova (formerly Cyberonics) VNS Therapy: The dominant implantable VNS platform. FDA-approved for drug-resistant epilepsy in 1997 and treatment-resistant depression in 2005. The current generation includes the SenTiva and AspireSR models. AspireSR introduced a responsive (closed-loop) feature: an integrated cardiac sensor detects ictal tachycardia (the heart rate spike that often accompanies a seizure) and automatically delivers an extra burst of stimulation. This responsive VNS reduces seizure severity by intervening during the seizure itself, rather than relying solely on scheduled stimulation. In clinical use, roughly 50-60% of epilepsy patients experience a meaningful reduction in seizure frequency (more than 50% reduction) after 1-2 years of therapy, though fewer than 10% become seizure-free.
For treatment-resistant depression, implantable VNS is typically reserved for patients who have failed multiple antidepressants and psychotherapy. Response rates in depression trials have been modest — roughly 30-35% response at one year — but the therapy is notable for sustained improvement over time, with some patients continuing to improve at 2-5 years post-implant.
Surgical procedure: Implantation requires general anaesthesia and takes approximately 1-2 hours. The surgeon makes two small incisions — one in the neck to wrap the electrode around the left vagus nerve, and one in the chest to place the generator. Risks include infection (2-3%), vocal cord paresis from nerve manipulation (1-2%, usually temporary), and the general risks of anaesthesia. The most common side effect of stimulation itself is hoarseness or voice alteration during the “on” periods, which occurs in roughly 60% of patients initially but often diminishes over months as the nerve adapts.
Non-Invasive VNS: gammaCore and Auricular Devices
gammaCore (electroCore): A handheld non-invasive VNS (nVNS) device applied to the skin over the cervical vagus nerve in the neck. The device delivers a proprietary waveform through two stainless steel contact surfaces. FDA-cleared for acute treatment of episodic cluster headache (2017), acute treatment of migraine (2018), and prevention of cluster headache. gammaCore is used on-demand — the patient holds the device against the neck for 2-minute stimulation sessions, typically 2-3 times during an attack. In the ACT1 trial for cluster headache, gammaCore achieved a response rate (pain freedom at 15 minutes) significantly higher than sham in episodic cluster headache, though results in chronic cluster headache were less robust. For migraine, the PRESTO trial showed that gammaCore reduced pain at 30 and 60 minutes compared to sham, though effect sizes were modest.
Transcutaneous auricular VNS (taVNS): These devices stimulate Arnold’s nerve (the auricular branch of the vagus) via electrodes placed on the ear — typically at the cymba conchae or tragus. Unlike gammaCore (which targets the cervical vagus trunk), taVNS works through the ear’s vagal afferent pathway. Several devices are available:
The Nemos system (tVNS Technologies/cerbomed) was one of the first taVNS devices, CE-marked in Europe for epilepsy and depression. Parasym (now Nurosym) is a consumer-oriented taVNS device marketed for autonomic regulation and well-being, with ongoing clinical trials. Multiple research-grade and consumer taVNS devices are now available, varying in electrode design, stimulation parameters, and clinical evidence.
The evidence base for taVNS is growing rapidly. A JAMA Network Open RCT (December 2024) demonstrated that taVNS significantly improved insomnia severity versus sham stimulation over 4 weeks. Additional trials have explored taVNS for post-stroke motor recovery, tinnitus, depression, and inflammatory conditions. However, most taVNS trials are still small (30-100 participants), and optimal stimulation parameters (frequency, pulse width, current intensity, duration, ear location) are not yet standardised.
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Bioelectronic Medicine: SetPoint Medical
SetPoint Medical represents a different paradigm: using VNS to treat inflammatory disease by activating the cholinergic anti-inflammatory pathway (CAP). Their implantable microregulator — a miniaturised device roughly the size of a pencil eraser — wraps around the cervical vagus nerve and delivers short daily stimulation sessions (1-5 minutes) designed to activate the splenic anti-inflammatory reflex: vagal efferents signal to the coeliac ganglion, which relays to the splenic nerve, triggering acetylcholine release from T cells in the spleen, which suppresses TNF-alpha and other pro-inflammatory cytokines.
In July 2025, SetPoint Medical received FDA approval for their bioelectronic medicine platform for rheumatoid arthritis — the first VNS device approved specifically for an inflammatory condition. The pivotal trial demonstrated significant improvements in disease activity scores compared to sham stimulation, with a favourable safety profile. This approval marked a milestone in bioelectronic medicine: proof that modulating the nervous system can treat autoimmune inflammation as effectively as some biologic drugs, with fewer systemic side effects.
How VNS Parameters Work
All VNS devices share the same basic principle — delivering electrical current to vagal nerve fibres — but differ in their parameters, which determine what fibres are activated and what physiological response is produced:
Frequency (Hz): The number of pulses per second. Implantable VNS for epilepsy typically uses 20-30 Hz. Lower frequencies (1-10 Hz) may preferentially activate large-diameter A-fibres (sensory), while higher frequencies recruit smaller C-fibres. taVNS research commonly uses 25 Hz, though this is not universally optimised.
Pulse width (microseconds): The duration of each individual electrical pulse. Typical range: 130-500 microseconds. Wider pulses recruit more nerve fibres but also increase the likelihood of side effects (particularly laryngeal stimulation causing voice changes).
Current intensity (mA): The strength of the electrical signal. Implantable VNS titrates upward over weeks from 0.25 mA to a typical therapeutic range of 1.0-2.5 mA. taVNS devices generally operate at lower currents (0.5-5 mA) because they must pass through skin, and patients self-adjust to just below pain threshold.
Duty cycle: The ratio of stimulation-on to stimulation-off time. Standard implantable VNS uses 30 seconds on / 5 minutes off (a 10% duty cycle). Closed-loop VNS devices can alter this dynamically based on physiological signals.
Closed-Loop and Next-Generation Systems
The most significant technological trend in VNS is the move from open-loop (fixed-schedule) to closed-loop (responsive) stimulation. Open-loop devices deliver the same stimulation pattern regardless of what the body is doing. Closed-loop devices monitor physiological signals — heart rate, EEG, inflammatory biomarkers, or other markers — and adjust stimulation in real time.
LivaNova’s AspireSR (cardiac-responsive VNS for epilepsy) was the first commercial closed-loop VNS system. Research is now exploring EEG-responsive VNS that detects pre-seizure brain activity patterns and intervenes before the seizure fully develops. In the inflammatory space, SetPoint Medical is developing closed-loop systems that adjust stimulation based on circulating cytokine levels or other inflammatory biomarkers. The Feinstein Institutes’ REVA project (completed July 2026) mapped the vagus nerve at fascicle-level resolution, which may enable future devices to target specific fascicles for specific organs — stimulating the gastric branch without affecting the cardiac branch, for example.
Consumer Devices vs. Medical Devices: What to Know
The consumer taVNS market has expanded significantly, with devices ranging from clinical-grade (Parasym/Nurosym, with ongoing RCTs) to generic ear-clip TENS units rebranded as “vagus nerve stimulators.” Key distinctions: FDA-cleared or CE-marked medical devices have undergone regulatory review for safety and have at least some clinical evidence. Generic TENS units applied to the ear are not designed for vagal stimulation and may not deliver appropriate parameters (frequency, pulse width, current) to effectively activate vagal afferents. The ear location matters — the cymba conchae has the densest vagal innervation; the earlobe has none (it’s used as a sham stimulation site in clinical trials for this reason).
If you’re considering a VNS device for a medical condition, discuss it with your clinician. Implantable VNS requires a neurologist’s recommendation and surgical implantation. gammaCore requires a prescription. Consumer taVNS devices are available without prescription but should still be used with informed guidance about appropriate parameters and realistic expectations.
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