Technical challenges and safety of magnetic resonance imaging with in situ neuromodulation from spine to brain

Functional Connectivity Magnetic Resonance Imaging Sequences in Patients With Postsurgical Persistent Spinal Pain Syndrome Type 2 With Implanted Spinal Cord Stimulation Systems: A Safety, Feasibility, and Validity Study

BACKGROUND

Chronic pain has been associated with alterations in brain connectivity, both within networks (regional) and between networks (cross-network connectivity). Functional connectivity (FC) data on chronic back pain are limited and based on heterogeneous pain populations. Patients with postsurgical persistent spinal pain syndrome (PSPS) type 2 are good candidates for spinal cord stimulation (SCS) therapy. We hypothesize that 1) FC magnetic resonance imaging (fcMRI) scans can be safely obtained in patients with PSPS type 2 with implanted therapeutic SCS devices and that 2) their cross-network connectivity patterns are altered and involve emotion and reward/aversion functions.

MATERIALS AND METHODS

Resting-state (RS) fcMRI (rsfcMRI) scans were obtained from nine patients with PSPS type 2 implanted with therapeutic SCS systems and 13 age-matched controls. Seven RS networks were analyzed, including the striatum.

RESULTS

Cross-network FC sequences were safely obtained on a 3T MRI scanner in all nine patients with PSPS type 2 with implanted SCS systems. FC patterns involving emotion/reward brain circuitry were altered as compared with controls. Patients with a history of constant neuropathic pain, experiencing longer therapeutic effects of SCS, had fewer alterations in their connectivity patterns.

CONCLUSIONS

To our knowledge, this is the first report of altered cross-network FC involving emotion/reward brain circuitry in a homogeneous population of patients with chronic pain with fully implanted SCS systems, on a 3T MRI scanner. All rsfcMRI studies were safe and well tolerated by all nine patients, with no detectable effects on the implanted devices.

Case report: The promising application of dynamic functional connectivity analysis on an individual with failed back surgery syndrome

Failed back surgery syndrome (FBSS), a chronic neuropathic pain condition, is a common indication for spinal cord stimulation (SCS). However, the mechanisms of SCS, especially its effects on supraspinal/brain functional connectivity, are still not fully understood. Resting state functional magnetic resonance imaging (rsfMRI) studies have shown characteristics in patients with chronic low back pain (cLBP). In this case study, we performed rsfMRI scanning (3.0 T) on an FBSS patient, who presented with chronic low back and leg pain following her previous lumbar microdiscectomy and had undergone permanent SCS. Appropriate MRI safety measures were undertaken to scan this subject. Seed-based functional connectivity (FC) was performed on the rsfMRI data acquired from the FBSS subject, and then compared to a group of 17 healthy controls. Seeds were identified by an atlas of resting state networks (RSNs), which is composed of 32 regions grouped into 8 networks. Sliding-window method and k-means clustering were used in dynamic FC analysis, which resulted in 4 brain states for each group. Our results demonstrated the safety and feasibility of 3T MRI scanning in a patient with implanted SCS system. Compared to the brain states of healthy controls, the FBSS subject presented very different FC patterns in less frequent brain states. The mean dwell time of brain states showed distinct distributions: the FBSS subject seemed to prefer a single state over the others. Although future studies with large sample sizes are needed to make statistical conclusions, our findings demonstrated the promising application of dynamic FC to provide more granularity with FC changes associated with different brain states in chronic pain.

The clinical value of using magnetic resonance contrast-enhanced three-dimensional nerve view in the diagnosis and management of sacral fracture accompanied by sacral plexus injury

BACKGROUND

The treatment of sacral fractures accompanied by nerve injury is complex and often leads to an unsatisfactory prognosis and poor quality of life in patients.

OBJECTIVE

The present study aimed to investigate the clinical value of using 3.0T magnetic resonance contrast-enhanced three-dimensional (MR CE-3D) nerve view magnetic resonance neurography (MRN) in the diagnosis and management of a sacral fracture accompanied by a sacral plexus injury.

METHODS

Thirty-two patients with a sacral fracture accompanied by a sacral plexus injury, including 24 cases of Denis spinal trauma type II and 8 cases of type III, were enrolled in the study. All patients had symptoms or signs of lumbosacral nerve injury, and an MRN examination was performed to clarify the location and severity of the sacral nerve injury. Segmental localization of the sacral plexus was done to indicate the site of the injury as being intra-spinal (IS), intra-foraminal (IF), or extra-foraminal (EF), and the severity of the nerve injury was determined as being mild, moderate, or severe. Surgical nerve exploration was then conducted in six patients with severe nerve injury. The location and severity of the nerve injury were recorded using intra-operative direct vision, and the results were statistically compared with the MRN examination results.

RESULTS

MRN showed that 81 segments had mild sacral plexus injuries (8 segments of IS, 20 segments of IF, 53 segments of EF), 78 segments had moderate sacral plexus injuries (8 segments of IS, 37 segments of IF, and 33 segments of EF), and 19 segments had severe sacral plexus injuries (7 segments of IS, 9 segments of IF, and 3 segments of EF). The six patients who underwent surgery had the following intra-operative direct vision results: 3 segments of moderate injury (IF) and 20 segments of severe injury (7 segments of IS, 10 segments of IF, 3 segments of EF). There was no statistically significant difference in the results between the intra-operative direct vision and those of the MRN examination (p> 0.05).

CONCLUSION

MR CE-3D nerve view can clearly and accurately demonstrate the location and severity of sacral nerve injury accompanied by a sacral fracture, and has the potential for being the first choice of examination method for this kind of injury, which would be of important clinical value.

Safety of Magnetic Resonance Imaging in patients under Sacral Neuromodulation with an InterStim Neuromodulator

OBJECTIVE

To retrospectively investigate the safety of magnetic resonance imaging (MRI) in patients under sacral neuromodulation (InterStim II).

METHODS

Data of patients who received a sacral neuromodulator at the urological department of a Swiss center of tertiary care from 2007 to 2018 and subsequently received at least 1 MRI with implanted device were retrospectively analyzed. Patient characteristics, data on implantation, MRI characteristics and complications potentially related to the MRI were analyzed. In addition, patient interviews were performed to verify the data gathered from patient records.

RESULTS

A total of 55 consecutive patients with a median age of 48 years (range 16 - 80 years) and a total of 191 MRIs (median 3, range 1 - 13) were included to the study. The majority of MRIs (92%) were performed with 1.5 Tesla. The majority of the 1.5 Tesla (58%) as well as 3 Tesla (56%) MRIs assessed body regions other than the head. Complication possibly related to the MRI were only found in 2 (1%) MRI scans in two patients who reported on transient electrifying pain and heat sensation at the implantation site of the neuromodulator during MRI.

CONCLUSION

MRI scans in patients with an implanted InterStim II sacral neuromodulator and with the device being turned off seem to be safe, even if they involve body regions other than the head, at least with 1.5 Tesla.

Multiple magnetic resonance imaging in patients with implanted sacral nerve stimulator

AIM

The aim of this study was to assess possible impacts of multiple magnetic resonance imaging (MRI) scans on the function of InterStim™ sacral neurostimulator systems (SNS; Medtronic Inc.) devices and on patient's safety.

METHODS

Over the course of 17 years, a total of 16 patients required 72 MRI examinations in various parts of the body. Each time an MRI was performed, the implanting urologist evaluated the SNS device function and deactivated the implant before the scan. Patients were monitored continuously during and after the procedure. After the MRI session, the site of the implanted device was examined, and the SNS device was reactivated.

RESULTS

None of the patients experienced pain or discomfort during or after the MRI scan. Impedances and stimulation amplitudes were recorded before and after MRI and showed no statistically significant changes regarding implant function. Micturition-time charts after MRI procedures were compared with previous records and showed no deviations either. No negative consequences of multiple MRIs have been observed.

CONCLUSION

This is the first report of patients successfully undergoing multiple MRI scans despite a previously implanted SNS. Sixteen patients underwent more than one MRI scan, with no negative effect on the functional outcome of SNS or negative side effects for the patients.

A Comprehensive Practice Guideline for Magnetic Resonance Imaging Compatibility in Implanted Neuromodulation Devices

OBJECTIVES

The evolution of neuromodulation devices in order to enter magnetic resonance imaging (MRI) scanners has been one of understanding limitations, engineering modifications, and the development of a consensus within the community in which the FDA could safely administer labeling for the devices. In the initial decades of neuromodulation, it has been contraindicated for MRI use with implanted devices. In this review, we take a comprehensive approach to address all the major products currently on the market in order to provide physicians with the ability to determine when an MRI can be performed for each type of device implant.

MATERIALS AND METHODS

We have prepared a narrative review of MRI guidelines for currently marketed implanted neuromodulation devices including spinal cord stimulators, intrathecal drug delivery systems, peripheral nerve stimulators, deep brain stimulators, vagal nerve stimulators, and sacral nerve stimulators. Data sources included relevant literature identified through searches of PubMed, MEDLINE/OVID, SCOPUS, and manual searches of the bibliographies of known primary and review articles, as well as manufacturer-provided information.

RESULTS

Guidelines and recommendations for each device and their respective guidelines for use in and around MR environments are presented.

CONCLUSIONS

This is the first comprehensive guideline with regards to various devices in the market and MRI compatibility from the American Society of Pain and Neuroscience.

Assessment of a Novel 3T MRI Compatible Cochlear Implant Magnet: Torque, Forces, Demagnetization, and Imaging

HYPOTHESIS

A novel cochlea implant (CI) device magnet providing alignment to the static field of a magnetic resonance imaging (MRI) will lead to reduced torque, longitudinal forces, and demagnetization effects. The image void and distortion will be comparable to those obtained with standard CI magnets.

BACKGROUND

MRI investigations of CI users pose several challenges such as magnet dislocation, demagnetization, and may cause pain. The presence of a CI magnet within MRI field causes image distortions and may diminish the diagnostic value of an MRI procedure. Objective of this work is to evaluate magnetic forces and imaging properties of the novel CI magnet within 1.5 and 3T MRI.

METHODS

Forces and torque of the novel CI magnet were measured in both 1.5 and 3T MRI and compared with the standard magnet in 1.5T. One cadaver head was implanted with the CI devices containing the novel and standard magnets in different configurations reflecting clinical scenarios and imaging properties were assessed and compared.

RESULTS

In particular the torque has been reduced with the novel CI magnet in comparison to the standard one. Both CI magnets have not shown any signs of demagnetization. The image void and distortion was comparable between the two magnets for the main MRI clinical scanning protocols in 1.5T MRI.

CONCLUSIONS

The novel CI magnet is safe to use for MRI investigations of CI users in 3T MRI without a need for bandaging and has acceptable level of image artefacts.

Special Considerations in Patients with Cranial Neurostimulatory Implants

Over the past 50 years, incredible progress has been made with implantable devices. Management can become complex, as unique issues arise with interaction of these devices with other devices and technologies. The cochlear implant (CI) is the most commonly implanted device in the head and neck. Because of its internal magnet, CIs can interfere with MRI, causing imaging artifacts, pain, and device complications. Other implants demonstrate similar issues with imaging and co-implantation. This article provides an overview of special considerations regarding neurostimulation devices within the head and neck. We focus on interactions between implantable devices and other technologies or devices.

[Cochlear implantation with deep brain or occipital nerve stimulation : Case studies for parallel application]

We were able to demonstrate that simultaneous treatment of a patient with a neuromodulation device for deep brain stimulation (DBS) or occipital nerve stimulation (ONS) plus a cochlear implant is a possible treatment option, and that both systems are able to work within their specifications without interference from each other. A large patient population with indications for both systems could profit from this in the future.

It's the little things: On the complexity of planar electrode heating in MRI

Neurological disorders are increasingly analysed and treated with implantable electrodes, and patients with such electrodes are studied with MRI despite the risk of radio-frequency (RF) induced heating during the MRI exam. Recent clinical research suggests that electrodes with smaller diameters of the electrical interface between implant and tissue are beneficial; however, the influence of this electrode contact diameter on RF-induced heating has not been investigated. In this work, electrode contact diameters between 0.3 and 4 mm of implantable electrodes appropriate for stimulation and electrocorticography were evaluated in a 1.5 T MRI system. In situ temperature measurements adapted from the ASTM standard test method were performed and complemented by simulations of the specific absorption rate (SAR) to assess local SAR values, temperature increase and the distribution of dissipated power. Measurements showed temperature changes between 0.8 K and 53 K for different electrode contact diameters, which is well above the legal limit of 1 K. Systematic errors in the temperature measurements are to be expected, as the temperature sensors may disturb the heating pattern near small electrodes. Compared to large electrodes, simulations suggest that small electrodes are subject to less dissipated power, but more localized power density. Thus, smaller electrodes might be classified as safe in current certification procedures but may be more likely to burn adjacent tissue. To assess these local heating phenomena, smaller temperature sensors or new non-invasive temperature sensing methods are needed.

Removal of Sacral Nerve Stimulation Devices for Magnetic Resonance Imaging: What Happens Next?

INTRODUCTION

Sacral neuromodulation (SNM) devices (Medtronic, Minneapolis, MN, USA) are not approved to undergo magnetic resonance imaging (MRI) of sites other than the head. When MRIs are required, devices are often removed prior to imaging. We reviewed the prevalence of device removal for MRI at a large academic institution and the subsequent clinical course of these patients.

METHODS

A retrospective review of all SNM explants from 2009-2015 was performed. Cases explanted for MRI were analyzed to collect demographics, clinical characteristics, and postremoval management. Descriptive statistics were calculated.

RESULTS

Ninety patients underwent SNM device removal, with 21 (23%) occurring for MRI. At explant, 20 patients (95%) were female and median age was 66 years. Suboptimal symptom control from SNM was noted in seven (33%) of these patients preoperatively. Of those explanted, six (29%) required MRI for neurologic and 10 (48%) for orthopedic concerns. The remaining MRI indications included abdominal masses (10%), genitourinary disease (5%), surveillance for prior malignancy (5%), and cardiac disease (5%). Only 16 (76%) patients explanted ultimately underwent MRI. MRI results impacted clinical management in 9/16 (56%) of the imaged patients. Only two (10%) of explanted patients underwent device replacement.

CONCLUSIONS

In patients receiving SNM therapy, device removal for MRI is most commonly due to orthopedic and neurologic pathologies. About half of the MRIs performed impacted non-GU clinical management. It is of paramount importance to confirm the necessity of MRI before removing a functional SNM device. Since SNM replacement was rare in this cohort, research is needed on the safety of various MRI types with SNM devices in vivo.

Bilateral globus pallidus internus deep brain stimulation for dyskinetic cerebral palsy supports success of cochlear implantation in a 5-year old ex-24 week preterm twin with absent cerebellar hemispheres

BACKGROUND

Early onset dystonia (dyskinesia) and deafness in childhood pose significant challenges for children and carers and are the cause of multiple disability. It is particularly tragic when the child cannot make use of early cochlear implantation (CI) technology to relieve deafness and improve language and communication, because severe cervical and truncal dystonia brushes off the magnetic amplifier behind the ears. Bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) neuromodulation can reduce dyskinesia, thus supporting CI neuromodulation success.

METHODS

We describe the importance of the order of dual neuromodulation surgery for dystonia and deafness. First with bilateral GPi DBS using a rechargeable ACTIVA-RC neurostimulator followed 5 months later by unilateral CI with a Harmony (BTE) Advanced Bionics Hi Res 90 K cochlear device. This double neuromodulation was performed in series in a 12.5 kg 5 year-old ex-24 week gestation-born twin without a cerebellum.

RESULTS

Relief of dyskinesia enabled continuous use of the CI amplifier. Language understanding and communication improved. Dystonic storms abated. Tolerance of sitting increased with emergence of manual function. Status dystonicus ensued 10 days after ACTIVA-RC removal for infection-erosion at 3 years and 10 months. He required intensive care and DBS re-implantation 3 weeks later together with 8 months of hospital care. Today he is virtually back to the level of functioning before the DBS removal in 2012 and background medication continues to be slowly weaned.

CONCLUSION

This case illustrates that early neuromodulation with DBS for dystonic cerebral palsy followed by CI for deafness is beneficial. Both should be considered early i.e. under the age of five years. The DBS should precede the CI to maximise dystonia reduction and thus benefits from CI. This requires close working between the paediatric DBS and CI services.

Recognizing the Common Origins of Dystonia and the Development of Human Movement: A Manifesto of Unmet Needs in Isolated Childhood Dystonias

Dystonia in childhood may be severely disabling and often unremitting and unrecognized. Considered a rare disorder, dystonic symptoms in childhood are pervasive in many conditions including disorders of developmental delay, cerebral palsy (CP), autism, neurometabolic, neuroinflammatory, and neurogenetic disorders. Collectively, there is a need to recognize the role of early postures and movements which characterize phases of normal fetal, infant, and child development as a backdrop to the many facets of dystonia in early childhood neurological disorders and to be aware of the developmental context of dystonic symptoms. The role of cocontraction is explored throughout infancy, childhood, young adulthood, and in the elderly. Under-recognition of pervasive dystonic disorders of childhood, including within CP is reviewed. Original descriptions of CP by Gowers are reviewed and contemporary physiological demonstrations are used to illustrate support for an interpretation of the tonic labyrinthine response as a manifestation of dystonia. Early recognition and molecular diagnosis of childhood dystonia where possible are desirable for appropriate clinical stratification and future precision medicine and functional neurosurgery where appropriate. A developmental neurobiological perspective could also be useful in exploring new clinical strategies for adult-onset dystonia disorders focusing on environmental and molecular interactions and systems behaviors.