Neuromodulation : journal of the International Neuromodulation Society
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Objectives. To evaluate magnetic resonance imaging-related (MRI-related) heating for the VNS Therapy System at 1.5 and 3 tesla (T) using various device configurations and MRI conditions and to assess device function before and after MRI. Methods. The VNS Therapy System (pulse generator, Model 102; leads Models 300 and 302; Cyberonics, Inc., Houston, Tex, USA) underwent assessment of MRI-related heating at 1.5 and 3 T using different positioning configurations, leads, transmit radiofrequency (RF) coils (body and head), RF power levels, and scans on different body regions. The function of the VNS Therapy System was evaluated before and after scanning. ⋯ Conclusions. MRI-related heating was characterized for a variety of scenarios, identifying unsafe as well as safe conditions. Device function was unaffected by MRI procedures at 1.5 and 3 T. By following specific conditions, safety guidelines for the VNS Therapy System may be expanded beyond those currently indicated by the manufacturer.
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Objective. To evaluate the ability to relieve shoulder pain by implanting ceramic-case versions of radiofrequency microstimulators (RFM) in paralyzed shoulder muscles. Materials and Methods. A 66-year-old man, who had left-sided chronic hemiplegia due to a stroke five years previously, had developed shoulder subluxation resulting in pain. Two RFM devices were implanted, one next to the axillary nerve and one at the motor point of the middle deltoid muscle. ⋯ Results. During the treatment period of six months of stimulation, the patient's pain had reduced from 70 to 0 on the VAS. At six months after completion of the treatment, pain relief and effective evoked muscle contraction have remained. Conclusion. Although these results suggest that the feasibility of using RFM devices implanted both epineurally to the axillary nerve and next to the muscle motor point in this one patient, to relieve pain and elicit contraction, further investigation is needed to demonstrate the clinical feasibility of using RFMs for treating poststroke shoulder pain.
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Experienced neurosurgeons at eight spinal cord stimulation centers in the United States, Canada, and Europe participated in a study from 1997 to 2000 investigating the safety, performance, and efficacy of a Transverse Tripolar Stimulation (TTS) system invented at the University of Twente, the Netherlands. This device was proposed to improve the ability of spinal cord stimulation to adequately overlap paresthesia to perceived areas of pain. Fifty-six patients with chronic, intractable neuropathic pain of the trunk and/or limbs more than three months' duration (average 105 months) were enrolled with follow-up periods at 4, 12, 26, and 52 weeks. ⋯ The most common complication was lead migration. While the transverse stimulation system produced acceptable outcomes for overall pain relief, an analysis of individual pain patterns suggests that it behaves like spinal cord stimulation in general with the best control of extremity neuropathic pain. This transverse tripole lead and driving system introduced the concept of electrical field steering by selective recruitment of axonal nerve fiber tracts in the dorsal columns.
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Objectives. There is ample and well-established evidence that direct electrical stimulation of the vagus nerve can change heart rate in animals and humans. Since tachyarrhythmias cannot always be controlled through medication, we sought, in this pilot study, to elucidate whether a clinical implantable lead system that is used in cervical vagus nerve stimulation therapy (VNS therapy) also can be used for control of heart rate, and tachycardia in particular. Materials and Methods. Experiments were carried out in three pigs (weight 21-26 kg) under general anesthesia. ⋯ No differences were found between stimulation of the right or left vagus nerve. Conclusion. VNS can be used effectively and rapidly to decrease heart rate, in acute settings, when connected to an external pacing system. Future devices that are fully implantable may be used for nonpharmacological treatment of illnesses in which tachycardia results in deterioration of cardiac function.
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Introduction. Spinal cord stimulation (SCS) is an effective procedure for the treatment of neuropathic extremity pain, with success rates approaching 70%. However, mechanical failures, including breakage and migration, can significantly limit the long-term effectiveness of SCS. A systematic analysis of surgical techniques was undertaken by a consensus group, coupled with extensive in vivo and in vitro biomechanical testing of system components. ⋯ Based on these findings, the panel recommended a paramedian approach, abdominal pulse generator placement, maximizing bend radius by pushing the anchor through the fascia, and anchoring of the extension connector near the lead anchor. Discussion. Several factors are important in longevity of SCS systems. We discovered that technical factors can make a large difference in SCS reliability and that strict attention to these "best practices" will provide the best chance for maintaining the integrity of SCS systems over the long term.