Peripheral Nerve Stimulation (PNS) uses mild electrical impulses to manage chronic pain and certain neurological conditions. This therapy offers an alternative for individuals seeking relief. Magnetic Resonance Imaging (MRI) provides detailed images of the body’s internal structures. Understanding the interaction between implanted medical devices, like PNS systems, and MRI’s strong magnetic fields is important for patient safety.
Understanding Peripheral Nerve Stimulation
PNS precisely delivers mild electrical pulses to specific peripheral nerves. These nerves extend throughout the body, outside the brain and spinal cord, acting as communication pathways for sensation and movement. A small electrical device, often with a wire-like electrode, is placed near the target nerve and sends controlled electrical impulses when activated.
PNS operates on neuromodulation, altering nerve activity to influence how the brain perceives signals. These electrical pulses interfere with pain signals traveling to the brain, effectively “scrambling” or masking the pain message. This stimulation may also promote the release of endorphins, the body’s natural pain-relieving chemicals. PNS treats chronic pain conditions, including neuropathic pain, persistent back pain, certain headaches, Complex Regional Pain Syndrome (CRPS), diabetic neuropathy, and post-surgical pain. Depending on the device, the stimulator’s battery may be external or implanted under the skin.
Ensuring MRI Safety with PNS Devices
Magnetic Resonance Imaging presents unique considerations for individuals with implanted medical devices like Peripheral Nerve Stimulators. MRI scanners use powerful static magnetic fields, rapidly changing gradient magnetic fields, and radiofrequency (RF) energy to generate detailed images. These forces can interact with metallic implants, potentially causing issues such as device heating, unintended movement or dislodgement, or device malfunction. Overheating of the leads, specifically at the lead-tissue interface, is a significant concern due to tissue damage risk.
To address safety concerns, medical devices are categorized with specific MRI compatibility labels. An “MRI Safe” designation indicates an item poses no known hazards in any MRI environment, typically because it contains no metallic or conductive components. “MRI Unsafe” items pose definite hazards and should not enter the MRI environment.
Most modern Peripheral Nerve Stimulation devices are classified as “MRI Conditional.” This means the device can be safely scanned under specific manufacturer-outlined conditions. These conditions include restrictions on the MRI scanner’s static magnetic field strength (e.g., 1.5 Tesla, 3.0 Tesla), maximum spatial gradient magnetic field, specific absorption rates (SAR), and allowed scan duration. Manufacturers conduct extensive testing, evaluating magnetic field interactions, potential heating, and induced electrical currents, to ensure devices meet safety standards.
Patient Guidance for MRI Scans
Patients with a Peripheral Nerve Stimulation device requiring an MRI scan must take specific steps to ensure safety. Inform all medical staff, including the MRI technologist and the ordering physician, about the implanted device. Provide the Patient Implant Card, which contains the device model number and manufacturer information.
Consult with the pain specialist or neurosurgeon managing the PNS device to confirm MRI compatibility and obtain specific manufacturer guidelines. The device will need to be programmed into an “MRI Mode” or have its stimulation turned off before the scan, done by a qualified clinician. In some cases, if the device is a temporary trial system or has non-functional leads, an MRI may be contraindicated due to increased risks.
During the MRI scan, patients might experience mild sensations such as tingling, vibration, or slight warming in the stimulator area. Immediately inform the MRI technologist if any discomfort occurs. After the MRI, the device will need to be checked, and therapy settings re-enabled or reprogrammed by a clinician to restore function.