Vagus nerve and spinal cord stimulators

A chest neurostimulator is not a pacemaker. For a VNS the magnet is the thing to know: hold it on to switch stimulation off, swipe it to give an extra dose.

Adult & paediatricNeurologicalGuideline

Also called: VNS, vagus nerve stimulator, vagal nerve stimulator, SCS, spinal cord stimulator, neurostimulator, neuromodulation device, LivaNova

What it is

These are neurostimulators, not cardiac devices, but they end up here because a vagus nerve stimulator (VNS) generator sits in the upper chest and looks like a pacemaker. The UK cardiac-device guidance warns directly that because neurostimulators are similar in outward appearance to a pacemaker this means that they may be mistaken for pacemakers.

A VNS treats drug-resistant epilepsy (and some depression) by intermittently stimulating the left vagus nerve via a lead in the neck. A spinal cord stimulator (SCS) treats chronic neuropathic pain via a lead in the epidural space and a generator usually in the buttock, flank or lower abdomen. SCS behaviour is device-dependent and is not covered by the VNS guidance below: most modern systems are switched with a patient handset, but some have a magnet-sensitive switch - so do not assume a magnet behaves the way it does for a VNS. The main ED issues for an SCS are MRI and diathermy compatibility; check the card and the pain / neuromodulation service.

VNS is used across ages - it is common in children with refractory epilepsy - so this entry is written for adults and children; SCS is essentially an adult device.

How to recognise it

VNS: a pacemaker-like generator in the upper left chest, with a lead running up to the left side of the neck; the patient has epilepsy (or less often depression) and usually carries a doughnut-shaped magnet or wristband magnet.
The patient or carer may describe using the magnet to abort a seizure, and may have hoarseness, cough or throat discomfort that comes in bursts - the Association of Anaesthetists guideline attributes these to recurrent laryngeal nerve stimulation and left vocal cord adduction during each stimulation.
SCS: a generator in the buttock, flank or lower abdomen with an epidural lead, in a patient with chronic pain, usually controlled by a handheld programmer (some systems also have a magnet switch - check, do not assume).
A device identification card naming a neurostimulator and the manufacturer (e.g. LivaNova for VNS) - which confirms it is not a cardiac device.

What it gets confused with

A pacemaker or ICD manages the heart rhythm; a VNS or SCS does not. A chest neurostimulator can look identical to a pacemaker, and the UK guidance flags exactly this trap. The giveaway is the lead going to the neck (VNS) rather than into the heart, and the patient's indication (epilepsy or chronic pain, not a cardiac rhythm problem). Do not apply cardiac magnet or pacing logic to it.

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What goes wrong

VNS stimulation causing airway or voice symptoms

Hoarseness, cough, throat tightness or breathlessness occurring in bursts with each stimulation cycle. Rarely, with a supraglottic airway in place, vocal cord adduction can obstruct the airway.

Red flag
The guideline notes VNS can cause unilateral vocal cord adduction with consequent airway obstruction in the presence of a supraglottic airway device. If stimulation is driving the symptoms, it can be stopped by holding the magnet over the generator (below); significant airway compromise needs a definitive airway.

VNS-associated bradyarrhythmia or hypotension

Uncommon, but bradycardia, hypotension, syncope and - rarely - asystole have been reported with left vagal stimulation.

Red flag
If the device is suspected of driving haemodynamic instability, deactivate it (hold the magnet on) and treat the bradycardia/hypotension conventionally. The guideline advises, in critical illness, cessation of vagus nerve stimulation and early consultation with neurology services.

Mistaken for a cardiac device

A chest generator is assumed to be a pacemaker or ICD, and cardiac magnet/pacing logic is applied to it.

Red flag
It has no effect on the heart rhythm. A cardiac magnet does the pacemaker/ICD things to a pacemaker/ICD; on a VNS a magnet does the VNS things below. Identify the device before acting.

The first ten minutes

Confirm what the device is from the card and the lead course (neck = VNS). If it is a VNS or SCS, it is not managing the heart.
For VNS symptoms driven by stimulation, use the magnet. The guideline states that continuous application of the magnet to the generator will deactivate the device, e.g. taping the magnet over the generator, whereas the magnet can be used to deliver an additional period of vagal stimulation to help terminate a seizure if swiped across the generator. Hold-on to switch off; swipe to dose.
If the patient's own VNS magnet is not to hand, the guideline notes that in an emergency situation, if a VNS magnet is unavailable, any magnet with a strength over 50 gauss can be used to deactivate the device - a standard pacemaker ring magnet will do.
Protect the airway if stimulation is obstructing it - deactivate with the magnet and intubate if there is significant compromise rather than relying on a supraglottic device.
Going to MRI? The device must be dealt with first: Vagus nerve stimulation devices must be deactivated in the MRI suite. That deactivation is programmed by the device / neurology service - a ring magnet must never be taken into the MRI suite (it is a projectile, and holding a magnet is not an MRI protocol). The same applies to an SCS, which is MRI-conditional at best; involve neurology / radiology and the device service.
Treat the actual emergency (the seizure, the pain crisis, the unrelated illness) conventionally, and involve neurology for the device.

Do not

Do not manage a chest neurostimulator as a pacemaker or ICD.

It does not touch the heart rhythm. The outward resemblance to a pacemaker is a known trap; applying cardiac magnet or pacing logic to it is meaningless and distracting.

Do not swipe a VNS magnet when you mean to switch stimulation off.

The two actions are opposite. Swiping the magnet across the generator delivers an extra burst of stimulation (to abort a seizure); only holding the magnet in place over the generator - taping it on - deactivates the device while it stays there.

Do not send a VNS or SCS patient to MRI without clearing the device first.

A VNS must be deactivated for MRI, and neurostimulators are at best MRI-conditional. Proceeding without checking risks device damage and patient harm. Involve neurology/radiology and the device service.

Who owns it

Neurology / neurosurgery (and the manufacturer's representative) own a VNS; the chronic pain / neuromodulation service owns an SCS. For acute haemodynamic or airway effects, involve critical care and anaesthesia. Tell them which device it is, the symptoms, whether you have applied a magnet, and whether MRI is planned.

What a magnet does to each device

This is the single most-confused fact in the whole tool, and it is dangerous because the same magnet does opposite things depending on the device. The rule beneath the table: a magnet suspends shocks on anything that can shock (ICD, CRT-D, S-ICD) and does nothing to stop pacing on anything that only paces - on a pacemaker it forces fast, asynchronous pacing. Always identify the device from its card before reaching for a magnet. Two caveats: the magnet response is not universal - a leadless pacemaker (Micra/Aveir) has no magnet sensor and the response can be programmed off, so no magnet response does not prove the device is inactive; and these rules apply to a child with one of these devices too (paediatric pad size, energy and specialist advice are not covered here).

ICD (including CRT-D, S-ICD): A magnet suspends shock therapy only while it is held in place - the guidance: Placing a strong magnet on the skin over the ICD generator will suspend tachyarrhythmia detection (and thereby suspend shock delivery). It does not stop pacing. Tape it on and check it stays: removal or displacement of the magnet will immediately restore the ability of the ICD to deliver a shock. One manufacturer (Biotronik) restores shocks after only 8 hours, so with that or an unknown device lift and replace the magnet periodically. Before applying the magnet for a shock storm, put external defibrillator pads on and get a rhythm strip - the magnet removes the safety net, so if the shocks are appropriate (VT/VF) you must be ready to defibrillate externally at once.
Pacemaker (and CRT-P): A magnet does NOT switch it off. It will not deactivate it but will cause the pacemaker to fire at a faster than usual rate and stops it being inhibited by the patient's own beats (asynchronous pacing). The guidance adds that magnets should not be used in a misguided attempt to deactivate a pacemaker. The one time a pacemaker magnet helps: if the pacemaker is being wrongly inhibited by oversensing (surgical diathermy, myopotentials, lead noise) and the patient is bradycardic or pausing, holding a magnet on forces asynchronous pacing and restores a reliable rate.
On a device that both paces and shocks: The magnet suspends the shock function only; pacing continues. The appendix states plainly: Magnet application does NOT affect the programmed pacemaker function of the device. So a magnet makes a pacing-dependent ICD patient no less paced - it only stops shocks.
Vagus nerve stimulator (VNS): Opposite logic to a cardiac magnet. Holding the magnet over the generator deactivates stimulation (continuous application of the magnet to the generator will deactivate the device); swiping it delivers an extra burst to abort a seizure. In an emergency without the patient's VNS magnet, any magnet with a strength over 50 gauss can be used to deactivate the device.
Loop recorder: Nothing to suspend - it delivers no therapy. A magnet is irrelevant to it.
After death with an active ICD: A magnet is only a temporary hold, not deactivation: Temporary deactivation using a magnet is not adequate before autopsy, device removal or cremation. A physiologist must deactivate the ICD, and if the patient has died with the magnet suspending shocks it must stay taped in place until they do. Note a brand that auto-reverts (e.g. Biotronik at 8 h) - after that the magnet protects no one, so tell the mortuary and device service.

Who to call

The team and the criteria are national. The phone number is local, and this tool does not know it. Find it once, now, and write it on the department's own card — that is the part no website can do for you.

Say the device name first: Open with laryngectomy, LVAD, shunt — the single word changes who comes and what they bring. Do not bury it in the history.
Say what you have already established: Whether the device is patent, whether it has been removed or disturbed, and what you have already tried. The specialist is deciding whether to walk or run.
Ask who owns it out of hours: Device ownership and the on-call route often differ from the implanting specialty, and it is frequently a regional centre rather than your own hospital.
The patient's own team is a resource, not an afterthought: Named nurse specialists, home-care companies and device helplines answer questions nobody else can, and the patient usually has the number.

When the device is not the problem

A patient with a device gets pneumonia, sepsis, pulmonary oedema and myocardial infarction at the same rate as everybody else. The device is the most visible thing about them and it attracts the whole assessment.

The NTSP says it out loud: The project's own manual warns that patients with tracheostomies can become unwell with all the problems that other patients get too. It is easy to become fixated with the tracheostomy. The same sentence applies to every device in this tool.
Clear the device, then leave it: Establish that the device is doing its job — the stoma is patent, the line draws back, the pump is running — and then assess the patient as you would anyone else.
The anchoring runs both ways: The opposite error is treating a device complication as a medical illness: a blocked gastrostomy read as vomiting, a baclofen pump failure read as sepsis.

NTSP manual — Red flags · read in full

What the patient will be carrying

VNS patients usually carry their own magnet (a doughnut on a wristband or watch) and a device card naming the manufacturer and settings. SCS patients carry a handheld programmer and a card. The card confirms the device is a neurostimulator, not a cardiac device.

Scope of this page

This page covers recognising a neurostimulator (especially a chest VNS that mimics a pacemaker) and the ED-relevant actions: using the VNS magnet correctly (hold to deactivate, swipe to dose), handling stimulation-driven airway/voice and haemodynamic effects, and the MRI caution. It does not cover programming, titration, or the management of epilepsy or chronic pain themselves, which belong to neurology and the pain service. VNS is used in adults and children; SCS is an adult device.