AUA 2018: Lumbosacral 1.5 Tesla MRI Compatibility with Sacral Neuromodulation

San Francisco, CA (UroToday.com) The use of sacral neuromodulation (SNM) devices is currently limited in patients who require magnetic resonance imaging (MRI) of sites other than the head, due to concerns about patient safety and device malfunction. Current product guidelines recommend explantation of all stimulation components if an MRI scan is required of sites other than the head, as the device contains ferromagnetic material that can be affected by the MRI magnet. However, the use of MRI has not been fully evaluated in patients with a SNM device. Currently, the InterStim II model (Medtronic, Minneapolis, MN) has FDA approval only for 1.5 Tesla (T) MRI head scans.

In the presentation on the Lumbosacral 1.5 Tesla MRI compatibility with Sacral Neuromodulation,” Juan M. Guzman-Negron, MD, of the Cleveland Clinic, reported results of an in-vivo study demonstrating the safety of InterStim systems during 1.5 T lumbar/pelvic MRIs. In this observational pilot study, his group demonstrated insignificant heating of InterStim systems during MRIs, with no impact on subsequent device function or therapeutic efficacy. 

Inclusion criteria for the observational study included patients aged 18 years and older with the model 3058 lead and a functional Interstim II implantable pulse generator in place, who required a lumbar/spine or pelvis 1.5 T MRI. Prior to the study, device interrogation was performed before and after the MRI study to evaluate impedances and battery life. Patients were required to complete validated questionnaires and a survey regarding their usual SNM sensation before and 1 month after the MRI scan. Prior to the MRI, all SNM devices were turned off and monitored during the MRI. After imaging, a survey containing 5-point Likert scales for sensations of heating, movement, and stimulation during the imaging was administered to participants.

Eleven patients were enrolled in the study, all of whom underwent lumbar/spine MRI for which the most common indication was lower back pain (6/11), as well as lower extremity weakness, pelvic pain, and buttock and leg pain. In all subjects, the SNM had been placed due to urinary urgency incontinence.

Interrogation of the SNM device pre and post-MRI revealed no change in threshold amplitude for neuro-stimulation, and no change in battery life. During the study, no patients revealed any sensation during the MRI scan. However, upon prompting after the MRI, one patient reported transient discomfort at the IPG site, and two patients recalled temporary warmth of the IPG site during the scan. There were no reports of any shock-like sensation, device movement, stimulation, or paresthesia during the MRIs. Furthermore, immediately after the MRI, no subjects reported pain at the IPG or lead sites. 1 month following the MRI, no participants recalled any pain or discomfort, movement, or abnormal stimulus sensation during the MRI, and only one of the two patients could recall temporary warmth of the IPG site during the scan. Significantly, there was no worsening of LUTS severity scores based on questionnaires before and 1 month after the scan. 

Based on the study’s findings, the authors posited that patients implanted with an InterStim II device could potentially undergo 1.5 T non-head MRI scans with minimal discomfort and no change in therapeutic efficacy. Although MRI-safe SNM devices is currently undergoing development, the study holds that for patients with currently available SNM devices, 1.5T non-contrast MRIs should not be contraindicated, and that device removal may not be necessary prior to a non-head MRI. 

Presented by: Juan M. Guzman-Negron*, Cleveland Clinic, Cleveland, OH
Co-Authors: Javier Pizarro-Berdichevsky, Pontifical Catholic University of Chile, Santiago, Chile, Bradley Gill, Cleveland Clinic, Cleveland, OH, Howard B. Goldman, Cleveland Clinic, Cleveland, OH

Written by: Judy Choi, MD, Assistant Professor, Department of Urology, University of California, Irvine @judymchoi at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA
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