tVNS for Prader-Willi syndrome

The short version

If you live with someone who has Prader-Willi syndrome, you know that the hardest part of the day is often not the food. It is the outbursts: explosive, exhausting, and able to decide where a person can live and what they can do. There are no approved drugs that target them, and most families have heard more promises than they can count.

tVNS is a small device with an electrode worn in the ear that delivers gentle electrical pulses to a branch of the vagus nerve. In the one published study of tVNS for PWS, four of the five adults who took part had significantly fewer and less severe outbursts after about nine months of daily use. Small study, not blinded, and we say so plainly. It is also the most encouraging evidence there is for a problem with very few answers, and the device is one of very few with a certified indication for PWS.

This page is written for families and carers, because in practice you are the ones who will run it. It says what the evidence shows, what twelve months of daily use looks like in a PWS household, and how we support you through them.

Who this is for

Prader-Willi syndrome affects roughly one in every 15,000 to 25,000 births. In the UK that is about 1,500 to 2,000 people, and the Prader-Willi Syndrome Association UK is in touch with most of the families. If you are one of them, PWSA UK is the right first place to ask about anything on this page; they know the condition, and they know us.

tVNS fits best when:

the person has genetically confirmed PWS and is aged 18 or over
temper outbursts are a major part of daily life
a carer or family member can run the device every day
a specialist team is involved, or can be
the household can commit to twelve months before judging

The device is intended for adults. The published study was in adults aged 22 to 41.

What we are trying to solve

PWS is caused by the absence of certain genes on chromosome 15. In infancy the picture is low muscle tone and feeding difficulty. From childhood on it shifts to hyperphagia, a relentless hunger that has to be managed through locked kitchens, meal plans and supervision, and to the emotional dysregulation that families describe as the most distressing feature of all.

Temper outbursts in PWS are not ordinary tantrums. They are intense episodes that can involve shouting, aggression, distress and self-injury, triggered by a change in routine, a thwarted expectation, or sometimes nothing anyone can name. They are a leading cause of placement breakdown and of a life lived smaller than it needs to be.

There is no approved treatment for them. Some clinicians use antidepressants or antipsychotics with variable results, but those were not designed for this. The toolbox is close to empty, which is why there is real interest in neuromodulation: the vagus nerve is wired into the brain circuits that regulate emotion and arousal, and those circuits are disrupted in PWS.

How it works, in plain English

A small branch of the vagus nerve surfaces in the outer ear, on a ridge called the cymba conchae. The tVNS electrode sits there and sends gentle pulses up the nerve to the brainstem, and on to the regions that handle arousal and emotional regulation.

Over months, stimulating the nerve appears to shift the nervous system toward a calmer, more regulated state. In the PWS study that showed up as fewer and milder outbursts. The researchers also measured heart rate variability, a marker of vagal tone, and found the device raised it, confirming a real physiological effect.

What tVNS has not been shown to do in PWS is reduce the hunger. An earlier study using an implanted stimulator did not achieve clear improvements in hyperphagia, and the tVNS study was designed around outbursts. There is a biological reason to hope, but the evidence is not there yet. We would rather you knew that now.

What the evidence shows

The published research on tVNS for PWS comes from a single group at the University of Cambridge, and the total sample is five adults. That is the honest picture.

Five adults with PWS, all with the paternal deletion subtype, used tVNS at home for twelve months, four hours a day.
Four of the five had statistically significant reductions in how often outbursts happened and how severe they were.
The improvement emerged after about nine months. That number matters more than any other on this page.
When the daily dose was cut from four hours to two, the outbursts came back in the people who had responded. That is one reason to think the effect was real and not just the attention of being in a study, and it is why we will remind you about the four hours at month six.
All four responders chose to continue after the study, and at informal follow-up years later reported continuing benefit.
Side effects in the study were mild: one person had skin irritation at the electrode site, which resolved.

What it does not show. There is no blinded, controlled trial yet. All five had the paternal deletion subtype, so we do not know about the other subtypes. All were adults.

A larger trial is under way. The VNS4PWS Phase 3 trial is randomised, double blind, and recruiting people aged 10 to 40 with genetically confirmed PWS. When it reports, it will be the first controlled evidence in this population.

The full evidence, for clinicians

The twelve months: what happens

Nine months is a long time to keep going without knowing. So we do not sell the device on its own; we sell twelve months of support with a checkpoint at month nine and a decision at month twelve, and we say from the start, repeatedly and without apology, that nine months is normal.

A conversation first. Ask us for a call and we phone you within three working days for 20 to 30 minutes. We check the four things the device must not be used with, including skin picking at the site, ask about the specialist team, and talk honestly about the wait. If we think tVNS is unlikely to help, we say so. Nobody asks for money on that call.
A baseline. For four weeks before the device arrives, you keep a simple behaviour diary: one line per outburst with the trigger, how long it lasted, and how intense, on a scale of one to five. We post you the printed diary. This is what the Cambridge families kept. No questionnaires.
The specialist team informed. We write to the team when you start, with the protocol and the review schedule, and we offer to talk to them directly.
A fitting call. By video, we get the electrode sitting right and the intensity comfortable, starting low because sensory sensitivity is common in PWS. Then the practical part: the session goes into the person's visual schedule as a fixed daily item, paired with something they enjoy that only happens with the electrode in, and we agree a picture-and-phrase card for the days the routine has to move. Rigid by design, because that is what the household runs on.
Scheduled calls. Month 1, for fit and tolerance. Month 3 and month 6, to look at the diary together without judging it yet. Month 6 is also when we remind you about four hours, because that is when households are tempted to ease off, and the study showed what happens when they do. Month 9, the checkpoint where the study saw change.
Summary sheets for appointments. Before each review we give you a one-page summary for the specialist team: adherence, diary totals, side effects, questions.
The decision at month twelve. You, the team and we look at the diary and name the outcome: a clear response, a partial response, or no response. In a household where outbursts drive placement decisions, a partial response may well be worth continuing; that is your call and the team's. If it has not helped, we say so and help you stop. We are finalising a supported evaluation period around that decision, and the terms will be published here when they are settled.

Each stage in more detail, and what it usually feels like for a family: Twelve months, month by month.

Any adverse event can be reported to us and to the MHRA's Yellow Card scheme.

Who it is not for

The Instructions for Use state that tVNS is intended for adults aged 18 and over. It should not be used by people who:

are pregnant
have an active implant, such as a cochlear implant, an implanted vagus nerve stimulator, or a cardiac pacemaker
have a cerebral shunt (for example, for hydrocephalus)
have sore or broken skin where the electrode would sit, so watch for skin picking at the ear

If there is a heart rhythm problem, talk to a doctor first. tVNS should be used under medical supervision.

Common questions

Will tVNS reduce the food-seeking behaviour? Based on the current evidence, no. The implanted VNS study in PWS did not achieve clear improvements in hyperphagia, and the tVNS study was designed around temper outbursts. The vagus nerve is involved in appetite signalling, so there is a biological reason to hope, but the clinical evidence is not there yet.

How long before we can tell if it is working? The published study saw meaningful improvement at around nine months. We ask families to commit to twelve months of daily use, with a checkpoint at nine, before judging.

Four hours a day, every day. Really? Yes, and the study is the reason: when sessions dropped to two hours the outbursts returned. The good news is that a fixed daily routine is something many people with PWS prefer, and the sessions can sit inside things that already happen every day, such as a favourite programme after tea.

Is the evidence strong enough to try? That depends on your situation. It comes from a small, unblinded study with encouraging but preliminary results. For a problem with almost nothing else on offer, many families and clinicians consider a safe, non-invasive option with a real signal worth a supervised try. The decision is yours and the team's, and we will give you a straight answer on the call.

Can children use it? The tVNS E Instructions for Use state the device is intended for adults aged 18 and over, and the published PWS evidence is in adults (aged 22 to 41). An ongoing trial includes younger participants from age 10, but using the device in a child would fall outside its current intended use and should only be considered with a specialist who knows the condition.

Does the person need a genetic diagnosis first? Yes. The published evidence and the ongoing trial both require genetically confirmed PWS. Without a confirmed genetic diagnosis, the evidence base does not directly apply.

How much does it cost? The device is £3,046.76 including VAT, which includes the starter consumables. It comes with the calls, the letters and the decision at month twelve described above. The how to access page has the detail and will carry the evaluation terms once they are settled.

What to do next

Ask us for a call. The form takes two minutes; choose "a family member or carer" if that is who you are. We phone you within three working days, and nobody asks for money on that call.
Raise it with the specialist team, or let us write to them. The clinician page below has the evidence in their language.
Talk to PWSA UK. They know the condition, they know the families who have tried this, and they will give you an independent view.

Request a call

For clinicians: the full evidence page

How to access tVNS

This page is for information only. It is not medical advice. Any decision about tVNS should be made with your clinician, who knows your full medical history.

tVNS is a Class IIa medical device manufactured by tVNS Technologies GmbH, Germany. Distributed in the UK by Anatomical Concepts UK Ltd.