Is there a safety issue with deep brain stimulators (DBS) and electromagnetic surveillance systems? Surgical placement of DBS has become more widely available as a therapy for a variety of movement disorders. Advanced security systems and other technologies that may affect the function of implanted neurostimulators present a growing concern. Specifically, individuals with movement disorders who have DBS may encounter alterations in device effects through everyday exposure to electromagnetic impulses. This article explores the implications of electromagnetic interference (EMI) for patients with DBS through supportive background information and a literature review.
Early surgical techniques for treating movement disorders that remain in use today include thalamotomy for tremor and pallidotomy for dystonia and for signs and symptoms of Parkinson disease. Prior to deep brain stimulation, stereotactic surgical ablation techniques were used to treat dyskinesia, dystonia, tremor, and Parkinsonian signs. Although effective, treating these disorders with surgical ablation of affected regions of the brain does not allow for postoperative adjustments following improved therapeutic response. Implanting a DBS device at specific sites allows for individualized programming of stimulator impulse amplitude and frequency for optimal symptom management. For example, a DBS may be placed in the thalamic region for tremor control, in the pallidal region for dystonia, and in the pallidal or subthalamic regions for Parkinsonian signs (Reynolds, Terry, Mark, Prieto, & Mueller, 2000).
Deep brain stimulation offers a system that is both reversible and programmable to control many signs and symptoms of movement disorder. As those are controlled, DBS afford an opportunity for lowering the medication dose and can consequently reduce or eliminate dyskinesias. DBS do not improve cognitive or psychiatric symptoms, on‐period freezing, swallowing difficulties, speech problems, or poor balance.
Therapeutic benefit is directly related to electrode placement precision. The subthalamic nucleus appears to be the most effective site for electrode contact in Parkinson disease (Hamel et al., 2003). The optimal electrode placement for symptom control for essential tremor, or possibly for tremor‐predominant Parkinson disease, is a specific site in the thalamus known as the ventral intermediate nucleus (Chen, Hua, Smith, & Shadmehr, 2006). Dystonia is most responsive to stimulation of the globus pallidus (Vidailhet el al., 2005). Brain mapping, scanning, and placement of electrodes in an awake patient allow for intraoperative confirmation of appropriate microelectrode placement for maximum benefit (Reynolds et al., 2000).
Despite its benefits, placement of DBS is not without risks (Medtronic, Inc., 2000). The Summary of Safety and Effectiveness Data for Supplemental Premarket Approval Application to the U.S. Food and Drug Administration (FDA) summarized DBS‐identified adverse effects as follows: Potential postoperative adverse effects include hemorrhage, infection, paresis/asthenia, and hemiplegia/hemiparesis. Stimulationrelated adverse effects may include dyskinesia, pain, speech problems, worsening of motor fluctuations, sensory impairment, visual disturbances, cognitive changes, respiratory changes, postural changes, vomiting, urinary incontinence, weight loss, sweating, accidental injury, sleep disturbances, neuropsychological disturbances, general paresis/asthenia, internal sensation of shock/jolt, cardiovascular events, hemiplegia/hemiparesis, and depression. Although these adverse events were listed by the manufacturer in the device application, the FDA concluded that, for a population of patients with Parkinson disease who have advanced levodopa‐responsive symptoms that are not adequately controlled with medication, the benefits of DBS outweigh the risks (U.S. Food and Drug Administration [FDA], 2002).
To avoid device damage or functional interference, neurological implanted electronic devices such as the deep brain stimulator should be turned off if exposure to an electromagnetic field is anticipated.
The following are specific examples of clinical data evaluations and numerous device improvements that have resulted in ongoing amendments to the DBS device approval. On July 31, 1997, the FDA granted a conditional approval for deep brain stimulation (i.e., implanted electrical thalamic stimulation system) for research, and on March 27, 1998, granted approval of the device contingent on further research safety and efficacy data. Final approval for commercial distribution of the device was filed by the FDA on September 30, 1999. On March 31, 2000, an expert FDA panel met regarding the Medtronic Activa Deep Brain Stimulator Parkinson's Control System. Upon consideration of safety concerns and expert opinion from medical professionals involved in the treatment of Parkinson disease, the panel concluded that the DBS had great promise and recommended that the FDA approve the device for patients with advanced Parkinson disease (Center for Devices and Radiological Health, 2000).
Further revisions due to safety concerns continue, following FDA approval. A DBS device instruction revision was prompted by a manufacturer recall on November 30, 2005, prompted by safety concerns with magnetic resonance imaging (MRI) of patients with the DBS (FDA, 2006b). Also relevant to other implantable devices, appropriate MRI safety screening and accommodations for imaging of persons with a device have been added to device guidelines referenced by MRI technicians.
The term electromagnetic impulses broadly refers to electrical, magnetic, and electromagnetic energy that surges from electronic or electromagnetic devices and is more prevalent near the generating machinery. Electromagnetic impulse interactions are most often noted when they cause interference with other electronic devices. Many incidents of suspected electromagnetic interference (EMI) with medical devices have been documented (Silberberg, 1993). As with all electronic devices, EMI can occur with a DBS device. Continued FDA device monitoring has resulted in fewer reports of EMI with the DBS than for spinal stimulators (SS).
Although the product label information from Medtronic includes internal sensation of shock/jolt as a potential adverse effect, the company does not specifically address electromagnetic effects on the stimulator. Clinician reports support a focus on patient education. Reynolds and colleagues (2000) recommended that patients be warned that electromagnetic fields emanating from machinery or metal detectors can turn off the stimulator. Although DBS were not mentioned specifically, a 1999 FDA consumer report indicated that security systems disrupt electronic devices; electronic medical devices may also be affected.
Kainz, Neubauer, Alesch, Schmid, and Jahn (2001) reported that metal detector gates at airports may switch neurostimulators, such as bladder, phrenicnerve, and upper‐ and lower‐extremity stimulators, into an asynchronous safety mode. However, effects of metal detectors on DBS have not been thoroughly investigated. The authors recommend further research on electromagnetic compatibility.
Increasing numbers of implantable electronic devices, coupled with the increasing prevalence of electromagnetic sources of interaction, support the assertion that the theoretical risk of interaction should not be excluded, and doctors and patients should be updated on potential interactions (Kainz et al., 2001). To avoid device damage or function interference, neurological implanted electronic devices such as the DBS should be turned off if exposure to an electromagnetic field is anticipated (Association of periOperative Registered Nurses, 2005). Electromagnetic fields may be encountered most commonly near security systems.
Boivin, Coletta, and Kerr (2003) noted that because of the higher‐pulse nature of magnetic fields, walkthrough metal detectors (WTMDs) pose a higher risk than handheld metal detectors (HHMDs). The standards set forth by the National Institute of Standards and Technology (NIST) for HHMDs and WTMDs state that electronic medical devices may have biological and interference effects caused by the magnetic fields generated by metal detectors (Paulter, 2002). According to NIST reports, HHMD and WTMD exposure limits are well within the standards of human exposure set by the National Institute of Justice. Even so, the effect of magnetic fields on implanted medical devices has not been studied extensively, so the safety precautions previously mentioned should remain in place until the FDA determines that exposure to magnetic fields from HHMDs and WTMDs is not unsafe (FDA, 2002).
Medtronic recently posted updated safety information on its Web site regarding SS and their potential for electromagnetic interaction with the neurostimulation system that can result in serious patient injury or death (Medtronic, Inc., 2006a). Warning information on the Medtronic Web site specific to the DBS device includes the fact that theft detectors and security screening devices may cause stimulation to turn on or off and may cause some patients to experience momentary increases in perceived stimulation (Medtronic, Inc., 2006b). This information supports the rationale for practitioners to recommend that patients with DBS turn off their device when anticipating exposure to electromagnetic interference. The FDA perspective on EMI and medical devices is that much work remains to be done to ensure electromagnetic compatibility and safety for persons with implanted electronic medical devices (Witters, 1995). Rapidly advancing technology complicates the potential for EMI and reinforces the necessity of cooperation from all parties (Witters).
Overstimulation and shock to patients with SS continue to be reported when patients are exposed to electromagnetic impulses emitted by security systems, metal detectors, and antitheft devices. Nine such adverse events have been reported to the FDA (Table 1); during the same period, 67 EMI events related to spinal stimulation were reported (Table 2). This disparity may be related to the broader applications for spinal stimulation along with the more recent SS coupled with the adoption of DBS as a therapeutic option for advanced Parkinson disease. Because the DBS and SS systems are essentially mechanically identical, the disparity is of significance. Although setting indications and implantation sites differ, the FDA (as well as device manufacturers and healthcare practitioners) recommends caution regarding electromagnetic impulse interference for patients with either device.
Safety reports and warnings about the electromagnetic effects on DBS are limited. Reasons include the fact that DBS are a relatively new therapy with a growing population of use and ongoing safety monitoring. In addition, because patients are taught how to turn their devices on or off as required, having it suddenly turned off by an electromagnetic impulse may seem serious to the patient. Lastly, a shock or jolt to the brain may not be perceived by the patient and consequently may not be viewed as an event that warrants reporting.
Implications for Nursing Practice
If a patient's device is turned off by an EMI, the impact may be more than an inconvenience for those who are unaware of this potential phenomenon. Specifically, turning off DBS results in the return of some or all of the physical symptoms the device is intended to treat. Resulting bradykinesia, rigidity, or tremor during a period of physical activity has the potential for significant safety risks. Patients report that their DBS turn off or require resetting when exposed to electronics that create an electromagnetic field. Such anecdotal reports include a broad array of items such as security systems from automobiles, retail stores, metal detectors, or even large speakers used for public presentations. Patients who experience EMI‐device malfunction should be empowered to anticipate when their device may be inadvertently turned off so that they can compensate with additional safety measures and be able to turn their device back on.
Many neurologists and neurology nurses consider that the EMI phenomenon is to be expected, and they often teach patients with DBS how to compensate for it. The incidence of this phenomenon is variable among individuals and is related to EMI exposure both through patients' lifestyles and the sensitivity of the specific device. With that in mind, it is important to proactively educate all patients who have the device. Proactive education of persons considering implantation of a deep brain stimulator should include the potential for EMI. Follow‐up programming appointments are the ideal setting for assessing the incidence of the interference problem and providing up‐to‐date education and reassurance. Nurses should use this information to educate current and potential patients with DBS about the possibility of stimulator failure that may result from casual exposure to electromagnetic impulses in the community and how to manage an interruption in device function.
Ongoing research regarding electromagnetic interactions with medical devices is necessary, as is educating patients about potential interactions before they consent to placement of DBS. Some people with DBS experience daily problems with EMI. EMI does not appear to present an immediate safety issue or device malfunction for people with DBS. However, the absence of sound research on the effects of EMI for DBS does not permit excluding it as a potential health concern. This and the lack of long‐term data on DBS therapy warrant further research. Meanwhile, healthcare professionals who care for patients with Parkinson disease who have DBS should routinely educate these patients about potential interactions and report their findings to the manufacturer and to the FDA to help promote public health and safety.
The clinical expertise of Paul Fishman, MD PhD, and Sharon Powell, MPH RN, enhanced the development of this manuscript.
Association of periOperative Registered Nurses. (2005, July). AORN guidance statement: Care of the perioperative patient with an implanted electronic device. AORN Journal,
Boivin, W., Coletta, J., & Kerr, L. (2003). Characterization of the magnetic fields around walk-through and hand-held metal detectors. Health Physics, 84
Center for Devices and Radiological Health. (2000). Neurological Device Panel Meeting Summary. Retrieved February 17, 2006, from www.fda.gov/cdrh/ndp.html
Chen, H., Hua, S., Smith, M., & Shadmehr, F. (2006). Effects of human cerebellar thalamus disruption on adaptive control of reaching. Cerebral Cortex, 16
Hamel, W., Fietzek, U., Morsnowksi, A., Schrader, B., Herzog, J., Weinert, D., et al. (2003). Deep brain stimulation of the subthalamic nucleus in Parkinson's disease: An evaluation of active electrode contacts. Journal of Neurology, Neurosurgery, and Psychiatry, 74
Kainz, W., Neubauer, G., Alesch, F., Schmid, G., & Jahn, O. (2001). Electromagnetic compatibility of electronic implants: Review of literature. Middle European Journal of Medicine, 113
Medtronic, Inc. (2000). Summary of safety and effectiveness data for a supplemental pre-market approval application
. Minneapolis, MN: Author.
Paulter, N. G. (2002, November). The National Institute of Justice standards for hand-held and walk-through metal detectors used in concealed weapon and contraband detection
. Gaithersburg, MD: National Institute of Standards and Technology (NISTIR Publication No. 6915).
Reynolds, N. C., Terry, L. C., Mark, L. P., Prieto, T. E., & Mueller, W. R. (2000). Too many treatments for Parkinson's disease: How should they be used? Wisconsin Medical Journal, 99
Silberberg, J. L. (1993). Performance degradation of electronic medical devices due to electromagnetic interference. Compliance Engineering,
Fall 1993, 25-39.
U.S. Food and Drug Administration (1999). Consumer report: Security systems may disrupt electronic devices.
Retrieved February 17, 2006, from www.fda.gov/fdac/departs/1999
U.S. Food and Drug Administration. (2002, January). Approval letter for P960009/S007. Rockville, MD: Author. Retrieved August 13, 2008, from www.fda.gov/cdrh/pdf/p960009s7.html
Vidailhet, M., Vercueil, L., Houeto, J., Krystkowiak, P., Benabid, A., Cornu, P., et al. (2005). Bilateral deep brain stimulation of the globus pallidus in primary generalized dystonia. New England Journal of Medicine, 352
Witters, D. (1995). Medical devices and EMI: The FDA perspective
. Rockville, MD: U.S. Food and Drug Administration, Center for Devices and Radiological Health.