Spinal Cord Stimulation Devices Can Pose Safety Concerns for Spine Surgery
The use of spinal cord stimulators (SCS), also referred to as neurostimulation, has increased in patients with spine-related chronic pain. In select patients, SCS is an effective treatment to manage various types of chronic pain such as post-laminectomy syndrome. Implantation of a SCS changes aspects of a patient’s structural anatomy that may pose challenges during spine surgery. Walsh pointed out that there currently is no accepted guideline that addresses safety issues related to perioperative assessment of patients who have a spinal cord stimulator. The purpose of their study is to improve surgical planning to reduce surgical risks.
There are three companies that presently market SCS devices in the United States. These three companies offer 16 types of pulse generators, 16 percutaneous SCS lead models, and 12 paddle lead models. Multiple combinations of these devices are often used to create many potential configurations for spinal cord patients.
The companies that market in the US recommend consulting their latest MRI guidelines for their neuromodulation systems before MRI is performed.
Medtronic (Medtronic, Inc., Minneapolis, MN): Certain models, lead/implant configurations, and MRI-conditional labeling may not be eligible for whole body scans.
Boston Scientific (Marlborough, MA): Certain lead/implant configuration is provided for head only conditional labeling; whole body MRI is pending.St. Jude Medical (St. Paul, MN): Whole body scans are pending.
About the Study
The authors performed an extensive literature review of FDA-approved spinal cord stimulation systems approved by the US Food and Drug Administration (FDA) on PubMed and on the FDA’s website. Articles were evaluated as to the safety concerns related to SCS devices in relation to preoperative evaluation (eg, MRI) and surgical management of patients with spinal cord stimulator implants.
Potential complications include:
- Risk of thermal injury during MRI
- Device dysfunction following MRI
- High dose radiation during CT scanning may shock the patient (rare)
- Monopolar electrocautery-related tissue damage
- Quality of intra-operative imaging (eg, fluoroscopy) may be limited by the neuromodulation device components
Magnetic Resonance Imaging (MRI)
With spinal cord stimulators, there is a risk of thermal injury due to induction of current by the magnetic fields during an MRI. No reports specifically show this type of injury in patients with SCS. However, one study reports the death of a patient secondary to the heating of a deep brain stimulator.
MRI safety recommendations vary between the models available. Only one of the three companies that market SCS systems in the United States allows for MRI imaging with a spinal cord stimulator implant. In fact, manufacturer recommendations for most SCS systems contraindicate the use of MRI.
Monopolar electrocautery is not recommended in patients with a spinal cord stimulator. However, in certain circumstances a surgeon may deem electrocautery as necessary. In these cases, it is important to make sure the SCS system has normal impedances and is turned off.
Bipolar electrocautery is recommended and may present with less risk. Bipolar delivery does not require a dispersive return electrode pad because both the active and return electrodes are integrated in the energy delivery forceps to a smaller, focused area.
The Aquamantys® System (Medtronic, Minneapolis, MN) is becoming more popular among spine surgeons. Studies have shown the system’s efficacy in reducing surgical blood loss and transfusion rates. This device uses Transcollation® technology that combines radiofrequency (RF) energy with saline irrigation to hemostatically seal tissue during spine surgery.
As spinal cord stimulation is increasingly utilized in patients with spine-related chronic pain, thorough preoperative evaluation may reduce risk of complications and improve surgical planning. The risks of MRI or electrocautery in patients with spinal cord stimulators should be carefully weighed against potential benefits.