Active Implants Other Than Cardiac Devices in MRI — Deep Brain, Spinal Cord, Vagus and Sacral Stimulators, Cochlear and Other Auditory Implants, Drug Infusion Pumps and Glucose Monitors: What the Evidence Shows and Where It Stops

Active Implants Other Than Cardiac Devices in MRI — Deep Brain, Spinal Cord, Vagus and Sacral Stimulators, Cochlear and Other Auditory Implants, Drug Infusion Pumps and Glucose Monitors: What the Evidence Shows and Where It Stops

MRIninja Knowledge Base | Child Page — MRI Safety (deep dive S7) Version 1.0 — October 2026

Parent page: MRI Safety — Master Page (hazard table in Section 3). Builds on: Implant and Device MR Safety Framework (test methods, label content, matching a label to the scanner) · Cardiac Implantable Electronic Devices in MRI (cardiac devices) · RF Heating and Burns (RF heating of leads)

1. Scope, Status and Boundaries

This page gathers the evidence on active implanted devices that are not cardiac: neurostimulators (deep brain, spinal cord, peripheral nerve, vagus and sacral nerve), cochlear and other active auditory implants, implanted drug infusion pumps, and body-worn or implanted glucose monitors and insulin delivery devices. It states what the sources read report about adverse events and about the conditions under which scanning has been done, and where those sources stop. Three neighbouring topics are held elsewhere and are not repeated: how a label is read and matched to the scanner, and the test standards behind it (Implant and Device MR Safety Framework); pacemakers, defibrillators and other cardiac devices (Cardiac Implantable Electronic Devices in MRI); and the mechanism of heating of leads and conductors (RF Heating and Burns). Passive implants and foreign bodies are the subject of Passive Implants and Retained Foreign Bodies in MRI.

Reading status. The page rests on the fifth edition (July 2026) of the UK MHRA guidelines (general sections read verbatim; Section 5.5 on implanted devices was not available in the text read), one national guideline module on hearing implants (Netherlands, 2024, read in Dutch), one systematic review and one overview on auditory implants (abstract level), a narrative review of neuromodulation, and clinical studies, case reports, a phantom study and manufacturer or institutional documents, nearly all at abstract level. No systematic review of MRI in deep brain, spinal cord or vagus nerve stimulation was read; a systematic review of MRI in vagus nerve stimulation appeared in search results but could not be accessed. No current manufacturer conditions are reproduced: they are specific to each model, they change, and they are held on the label and the manufacturer’s MRI guidance for the device in front of the operator.

What this page does not do. It gives no scanning conditions to be applied to a patient, because the label of the exact implanted system is the authority (Implant and Device MR Safety Framework). Statements that are the page’s own inference are marked Reasoning; where a source needed to complete a statement was not found they are marked (to be sourced).

2. Sources Read and What They State

Table 1. Documents used and how they were read.

3. Hazards Common to Active Implants

The MHRA guidelines state that the effects of the MR environment can adversely affect medical equipment, including passive and active implantable medical devices, and name stimulation systems (deep brain, sacral nerve or vagus nerve stimulation) as examples; the effects listed are device malfunction (possible effects include device reset, battery drain and permanent damage, with serious consequences for patients who are dependent on the device), movement of the implant within the body with possible tissue damage, heating (gradient-induced eddy currents in implants), and unintended stimulation from voltages induced in leads or circuitry [1]. For devices with leads or electrodes the guidelines state that there is an increased potential for localised burns or SAR hot spots, and that the B1+rms limit is most often found in the labelling of MR Conditional implants [1]. They also state that the operating modes do not in isolation consider the risk from implants, and that for MR Conditional implants exposure risks are minimised by adhering to the manufacturer’s instructions [1]. The standard behind such labelling and the meaning of the label content are in Implant and Device MR Safety Framework.

Table 2. Hazard by device group and where the evidence is reviewed below.

Reasoning. The hazards are the same four for every device in this page; what differs is which one dominates in the published reports. For stimulators with leads the evidence is mostly about heating and about whether a device can be put into its MR-conditional state; for cochlear implants it is about the internal magnet; for pumps it is about the mechanism of the motor; for glucose monitors it is about classification. This is the page’s own summary of the sections that follow.

4. Deep Brain Stimulation

A narrative review describes the labelling history: in 2002 the manufacturer required head-only transmit and a SAR of 0.4 W/kg, revised in 2005 to 0.1 W/kg, with extended labelling in 2015 for eligible devices that allows a B1+rms-based condition with body-coil transmit [5]. The same review reports that patient series described few or no adverse incidents attributable to the MR environment, and cites two published cases of harm when scanning was outside the prescribed conditions: a permanent neurological deficit and a transient dystonia [5]; the original reports were not read. An earlier review stated that manufacturer restrictions had been little tested and that very few detailed investigations of heating had been published [9].

Table 3. Evidence on deep brain stimulation read for this page.

Reasoning. Zero events in 102 participants is compatible with a true event rate of up to about 3 per cent (rule of three applied by this page to participants, not to scans; the abstract gives neither the number of scans nor the devices). The series show that events were not seen under local safety testing; they do not show that scanning outside the labelled conditions is safe, and the phantom study shows that heating depends on field strength and transmit mode.

5. Spinal Cord and Peripheral Nerve Stimulation

A compilation of data collected by direct communication with ten neurostimulation companies up to December 2024 reports that full-body 1.5 T is standard across most spinal cord stimulation systems, that some systems permit 3 T, and that limits vary by manufacturer: spatial gradient limits of 1,000 to 4,000 gauss/cm, SAR limits and active scan times of 15 to 60 minutes; peripheral nerve stimulation systems show similar patterns [11]. The authors note that no central source of this information existed and that it will need continued updating [11]. The narrative review of about 2016 described several systems as labelled for head-transmit only at 1.5 T and others for whole-body transmit at 1.5 T, and reported safe MRI in two patient series of spinal cord stimulation [5]; the difference from the later compilation illustrates how fast labelling changes.

A label can be unusable in an individual patient. In a case series of three patients the spinal cord stimulator could not be placed in its MRI-conditional mode because of high impedance; all three needed alternative imaging (including CT) and two had the system explanted [12]. The authors state that the cause of high impedance is incompletely understood and that impedance changes can have device-related and physiological causes [12].

Reasoning. Because the conditional mode has to be enabled in the device before the scan, the label cannot be applied by the scanner operator alone: the check that the device can reach its MRI mode belongs to the pathway before the examination. The sources read do not describe who performs this check or how it is documented (to be sourced).

6. Vagus and Sacral Nerve Stimulation

The only source read that covers these devices is the narrative review of about 2016: vagus nerve stimulation labelled for 1.5 T or 3 T with a head-only transmit coil, an early report of 25 patients at 1.5 T without permanent adverse effects, and a sacral nerve system permitting head-only transmit at 1.5 T [5]. No counts or rates for sacral nerve stimulation are reported in that source, and the labelling is a snapshot that may have changed [5]. The evidence on these devices in the sources read is therefore limited to a labelling description and a single early series (to be sourced: a current review or the manufacturer conditions).

7. Cochlear and Other Auditory Implants

7.1 Pooled and Single-Centre Evidence

A systematic review of 14 observational studies (10 retrospective, 4 prospective; searches to March 2024) reports 814 MRIs in 668 implanted ears with 167 adverse events (20 per cent); pain accounted for 51 per cent of the events, magnet displacement for 22 per cent and polarity reversal for 2 per cent; no adverse events were reported with diametric magnets, events were more frequent with axial magnets, and most occurred at 1.5 T, a bias of the literature that limits comparison [3]. The abstract does not itemise the remaining quarter of events. Mitigating measures (head wrapping, anaesthesia, anxiolytics) were common and not uniformly effective, and paediatric patients were under-represented [3]. Figure 1 shows the composition.

Figure 1 — Adverse events after MRI in cochlear implant recipients: composition reported by a systematic review

A prospective review of 14.5 years at one centre (97 patients, 428 sessions at 1.5 T) reports that magnets were removed in 28 sessions (6.5 per cent), that there were 15 complications (3.5 per cent of sessions), mostly discomfort, with five magnet dislocations and no implant failure or excessive demagnetisation, and the authors conclude that MRI was generally safe and well tolerated without magnet removal [14]. An earlier retrospective record review of 18 patients and 30 examinations reported that five patients with head bandages could not finish their scans because of pain, that one of them had magnet displacement, that another needed surgery to remove and reinsert the magnet, and that one patient had a polarity reversal [13]. An overview of the topic states that adverse events still occur although more MRI-conditional active hearing implants are available, and that older devices often have more restrictive labelling, which can cause confusion [4].

7.2 The Dutch National Guideline

The Dutch module (2024) recommends following the manufacturer’s MR conditions; for cochlear implants it distinguishes devices that can be scanned without a bandage (scheduled at 1.5 T or 3 T according to the question and the manufacturer’s conditions) from those that are scanned after a bandage and splint (local procedure), refers to the implanting centre when the magnet must be removed and no alternative imaging is possible, and recommends staff training and a written local procedure before bandaging; for auditory brainstem implants it refers fixed-magnet devices to the implanting centre; for percutaneous bone conduction implants it allows scanning at 1.5 T and 3 T without further conditions; for transcutaneous bone conduction and active middle ear implants it requires identification of supplier and model and adherence to the supplier’s conditions; and for passive middle ear implants it allows 1.5 T or 3 T without restrictions [2]. The guideline states that it found no comparative patient studies, so GRADE could not be applied; that the evidence is expert consensus, a systematic review of 38 studies (pain the most frequent adverse event, magnet dislocation the most frequently reported device problem) and four small non-comparative studies in which dislocation rates varied strongly by implant type (about 30 per cent with one implant series in two studies, none in about 40 procedures in a third); that the incidence of risks cannot be estimated because the number of MRIs performed is unknown; and that the bandage recommendations rest on expert experience [2].

Table 4. Cochlear implant evidence side by side.

Reasoning. The sources do not agree on a single rate because they count differently (events per implanted ear, complications per session, patients unable to finish), cover different devices and eras, and differ in whether a bandage was used. What they agree on is the ranking: pain and magnet displacement dominate, axial magnets are involved more than diametric ones in the pooled data, and harm to hearing was not reported in the series read. The review of single-centre series cannot say how many displacements went unreported.

8. Implanted Drug Infusion Pumps

A manufacturer guide for one family of programmable intrathecal pumps states conditions for 1.5 T and 3 T cylindrical scanners, a maximum spatial field gradient of 19 T/m, a slew rate of 200 T/m/s or less per axis, the First Level Controlled Operating Mode, and that the risk of heating increases for active torso scanning over 30 minutes [15]. The guide describes motor stall during the scan, with recovery typically detected within 20 minutes of the end of the scan and, for pumps delivering at least 0.048 mL/day, restart of infusion possibly delayed by up to 24 hours; states that a pump aligned 90° to the scanner’s z-axis carries a risk of permanent motor stall; advises deciding before the scan whether the patient can go without drug delivery during it, that stopping the pump is not recommended, and that the current infusion parameters be recorded; requires that all pumps be interrogated after the scan, with a second interrogation possibly needed to detect stall recovery; and warns that baclofen withdrawal can be life-threatening [15].

A case report adds a patient with several MRIs and a pump of the same family who had two memory failures with withdrawal symptoms (one resolved by a memory reset, the second needing pump replacement 29 months later); the authors state that MRI can temporarily stop the rotor and that every patient with an implantable drug delivery system should have the pump interrogated after MRI, with particular attention to baclofen [16].

Reasoning. The guide applies only to the models it names; other pumps (including those used for other drugs or with other mechanisms) have their own conditions. The consequence of a stalled or reset pump depends on the drug, which is why the same label-based pathway needs a drug-specific step. No independent study of pump function after MRI was read (to be sourced), and the case report cannot show how common memory errors are.

9. Glucose Monitors and Insulin Delivery Devices

The only source read on these devices is a web page of one UK department: one implanted-sensor system is classified as MR Conditional in the UK with its external transmitter MR Unsafe and to be removed; a second sensor system is not MR Conditional in the UK but may stay in place off-label under a local risk assessment and signed consent, citing the manufacturer’s US conditions; all other glucose monitors are classified MR Unsafe and are to be removed before scanning [17]. The page states that the risk of keeping the second system in place “has been demonstrated to be low” without giving the data, cites no published evidence, and does not mention insulin pumps [17].

No published study, guideline or manufacturer document on insulin pumps was read for this page (to be sourced). The MHRA text read does not mention them [1]. Because these devices are worn on the body and are normally removable, the usual question is whether and how they are removed and reapplied, which the sources read do not settle.

10. Practice: the Pathway the Sources Support

Reasoning. The following arrangement is the page’s synthesis of statements in the sources and is not itself a recommendation of any one source. (1) Identify every implanted component and its model, including leads, extensions and any abandoned parts, and read the label for the complete system rather than for the generator alone (Implant and Device MR Safety Framework; the MHRA states that the manufacturer’s instructions are the basis of risk minimisation [1]). (2) Confirm that the device can be put into its MRI mode and that the conditions of the label can be met for the intended anatomy; the label may be unusable in the individual patient [12]. (3) Apply the device-specific steps required before and after the scan: for drug pumps the recording of infusion settings and the interrogation afterwards [15]; for cochlear implants the local bandaging procedure and the patient information on discomfort [2]. (4) Treat any scan outside the label as an exceptional, documented risk-benefit decision, noting that published off-label scanning without harm exists but cannot establish safety for others [7, 10]. The sources read do not say who performs each step or how it is recorded (to be sourced).

11. Where the Documents Differ and Open Questions

Table 5. Differences and unresolved questions.

12. Limits of the Evidence and What Was Not Read

The evidence is mostly single-centre series, case reports, phantom studies and manufacturer documents; one systematic review (cochlear implants) was read at abstract level, and no systematic review for the other device groups was read. MHRA Section 5.5, the ACR Manual on MR Safety, ISO/TS 10974 and the manufacturers’ current conditions were not read. Events in small series cannot establish the absence of risk, passive reports and unreported displacements are not captured, and the evidence is concentrated at 1.5 T. The statements on labelling are snapshots and must not be applied without the current label of the exact system.

13. Topics Not Covered

Label content, test standards and matching a label to the scanner (Implant and Device MR Safety Framework); cardiac devices (Cardiac Implantable Electronic Devices in MRI); heating of conductors and burns (RF Heating and Burns); passive implants, aneurysm clips and foreign bodies (Passive Implants and Retained Foreign Bodies in MRI); pregnancy and staff exposure (MRI in Pregnancy and the Pregnant Worker); sedation, monitoring and the care of a patient with an implant during the scan (Claustrophobia, Sedation, Monitoring, Equipment and Emergencies in the MR Environment); deep brain stimulation research at ultra-high field; programming and stimulation-related effects of the scan on symptoms; and the rules of individual jurisdictions (Incident Learning, Governance, Quality and Jurisdictions in MR Safety).

14. Evidence-Based References

One systematic review (cochlear implants) and one overview were read at abstract level; no systematic review of MRI in deep brain, spinal cord or vagus nerve stimulation was read. The sections below follow the hierarchy of the sources actually read.

A. Guidelines, Consensus, Standards and Regulation

B. Systematic Reviews, Overviews and Narrative Reviews

C. Clinical Studies, Case Series and Case Reports (read at abstract level)

D. Technical Studies and Manufacturer or Institutional Documents

End of document — Active Implants Other Than Cardiac Devices (S7) — MRIninja v1.0 — October 2026. Parent: MRI Safety master.