title: A histological analysis of human median and ulnar nerves following implantation of Utah slanted electrode arrays.
abstract: For decades, epineurial electrodes have been used in clinical therapies involving the stimulation of peripheral nerves. However, next generation peripheral nerve interfaces for applications such as neuroprosthetics would benefit from an increased ability to selectively stimulate and record from nerve tissue. This increased selectivity may require the use of more invasive devices, such as the Utah Slanted Electrode Array (USEA). Previous research with USEAs has described the histological response to the implantation of these devices in cats and rats; however, no such data has been presented in humans. Therefore, we describe here the degree of penetration and foreign body reaction to USEAs after a four-week implantation period in human median and ulnar nerves. We found that current array designs penetrate a relatively small percentage of the available endoneurial tissue in these large nerves. When electrode tips were located within the endoneurial tissue, labels for axons and myelin were found in close proximity to electrodes. Consistent with other reports, we found activated macrophages attached to explanted devices, as well as within the tissue surrounding the implantation site. Despite this inflammatory response, devices were able to successfully record single- or multi-unit action potentials and elicit sensory percepts. However, modifying device design to allow for greater nerve penetration, as well as mitigating the inflammatory response to such devices, would likely increase device performance and should be investigated in future research.
authors.affiliation: Department of Bioengineering, College of Engineering, University of Utah, 36 S Wasatch Dr, Rm 3100, Salt Lake City, UT 84112, USA. Electronic address: Ben.christensen@utah.edu.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Christensen
authors.affiliation: Department of Bioengineering, College of Engineering, University of Utah, 36 S Wasatch Dr, Rm 3100, Salt Lake City, UT 84112, USA.
authors.forename: Heather A C
authors.initials: HA
authors.lastname: Wark
authors.affiliation: Department of Orthopaedics, School of Medicine, University of Utah, 30 N 1900 E, Salt Lake City, UT 84132, USA.
authors.forename: Douglas T
authors.initials: DT
authors.lastname: Hutchinson
mesh_terms: D000200:Action Potentials; D000672:Amputation Stumps / Q000473:pathology; D000893:Anti-Inflammatory Agents / Q000494:pharmacology / Q000627:therapeutic use; D019072:Antibiotic Prophylaxis; D001369:Axons / Q000648:ultrastructure; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods; D004567:Electrodes, Implanted / Q000009:adverse effects; D005542:Forearm / Q000601:surgery; D005549:Foreign-Body Reaction / Q000209:etiology / Q000473:pathology; D006801:Humans; D008262:Macrophage Activation; D008475:Median Nerve / Q000293:injuries / Q000473:pathology / Q000648:ultrastructure*; D008839:Microelectrodes / Q000009:adverse effects; D008855:Microscopy, Electron, Scanning; D009186:Myelin Sheath / Q000648:ultrastructure; D010525:Peripheral Nerves / Q000648:ultrastructure; D010591:Phantom Limb / Q000503:physiopathology*; D012677:Sensation; D014459:Ulnar Nerve / Q000293:injuries / Q000473:pathology / Q000648:ultrastructure*
chemical_list: D000893:Anti-Inflammatory Agents
keywords: Foreign body response; Human; Microelectrode; Neural prosthesis; Peripheral nerve