PNS Implants and MRI: What Patients Need to Know

People living with chronic joint pain are also, frequently, people who need ongoing medical imaging. Evaluating disease progression, checking for infection, assessing soft tissue or bone health — these are routine clinical needs that rely on MRI. For a patient with an implanted device, the question of MRI access is a practical, important one.

Historically, this was a significant limitation of implanted neurostimulation systems. Older devices were often classified as MRI-unsafe, or required such restrictive conditions that MRI access was effectively unavailable. This created real clinical problems: patients with spinal cord stimulators or early-generation neurostimulators were cut off from a critical diagnostic tool.

The concern with implanted electronic devices and MRI is not unfounded. MRI uses powerful magnetic fields and radiofrequency energy to produce images. These can interact with implanted metals and electronics in several ways: heating of leads, unintended movement of ferromagnetic components, induced currents through electrode wires, or interference with device function.

For older neurostimulation systems, these risks were serious enough that MRI was contraindicated. The physical design of early systems — with large pulse generators containing batteries and metallic housing — made MRI interaction a genuine safety hazard.

Modern peripheral nerve stimulation systems have been designed with MRI access as a priority. Several current-generation PNS devices have received FDA labeling designating them as MRI-conditional — meaning they can be safely used in MRI environments under specific, defined conditions.

A key factor enabling better MRI compatibility in some newer devices is the separation of the power source from the implant. Systems that place the battery or power source externally — rather than implanting it with the leads — eliminate one of the primary sources of MRI concern. A small, passive implanted component with no internal battery interacts very differently with MRI fields than a large active pulse generator.

'MRI-safe' means a device poses no known MRI-related hazards under any conditions. This designation is rare for implanted electronics. 'MRI-conditional' — the more common and more relevant designation — means the device can be safely used in MRI under specific, documented conditions: typically a defined magnetic field strength (e.g., 1.5 Tesla or 3 Tesla), specific scanning parameters, and lead/implant positioning requirements.

Patients and physicians should not interpret 'MRI-conditional' as 'MRI-unrestricted.' Each scan must be evaluated against the device's specific labeling, and the radiologist and MRI technician must be informed of the implant before scanning begins. This is not optional — it's a patient safety requirement.

Any patient with an implanted PNS system must inform their ordering physician, radiologist, and MRI facility about the implant before scheduling. The MRI team will review the device's manufacturer labeling — typically accessible through the manufacturer's website or via your implanting physician — and determine whether the requested scan is compatible.

Your implanting physician or their clinic should have documentation of the specific device model and its MRI labeling. Keeping a copy of this information readily accessible is strongly recommended. In urgent imaging situations, the ability to quickly communicate your implant details can be critical.

One meaningful advantage of modular PNS designs — where the external wearable component can be upgraded independently of the implanted components — is that improvements in MRI compatibility at the system level may become accessible without requiring additional surgery to replace the implanted portion.

As manufacturers continue to refine both device design and MRI safety testing, the landscape for implanted neurostimulation and MRI access is improving. Patients should discuss current MRI compatibility of any device they're considering with their physician during the evaluation process.