Evaluation of Electromagnetic Incompatibility Concerns for Deep Brain Stimulators

Kelly Dustin


J Neurosci Nurs. 2008;40(5):299-303. 

In This Article

Literature Review

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. Stimulation-related 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, neuro-psychological 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).

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 stimu-lation 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, phrenic-nerve, 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, walk-through 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.


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