Lee Fisher, PhD, Publishes Research in the Journal of Neural Engineering and Journal of Surgical Case Reports

January 6, 2022

Lee Fisher, PhD, assistant professor, UPMC Department of Physical Medicine and Rehabilitation, and colleagues published “Stimulation of the dorsal root ganglion using an Injectrode®” in the Journal of Neural Engineering and “Surgical placement of customized abdominal vagus nerve stimulating and gastrointestinal serosal surface recording electrodes” in the Journal of Surgical Case Reports in fall 2021.

Stimulation of the Dorsal Root Ganglion Using an Injectrode®

The goal of this study was to compare afferent fiber recruitment by dorsal root ganglion (DRG) stimulation using an injectable polymer electrode (Injectrode®) and a more traditional cylindrical metal electrode. The team exposed the L6 and L7 DRG in four cats via a partial laminectomy or burr hole. They stimulated the DRG using an Injectrode or a stainless steel (SS) electrode using biphasic pulses at three different pulse widths (80, 150, 300 μs) and pulse amplitudes spanning the range used for clinical DRG stimulation.

The research team recorded antidromic evoked compound action potentials (ECAPs) in the sciatic, tibial, and common peroneal nerves using nerve cuffs. They calculated the conduction velocity of the ECAPs and determined the charge-thresholds and recruitment rates for ECAPs from Aα, Aβ, and Aδ fibers. They also performed electrochemical impedance spectroscopy measurements for both electrode types.

The ECAP thresholds for the Injectrode did not differ from the SS electrode across all primary afferents (Aα, Aβ, Aδ) and pulse widths; charge-thresholds increased with wider pulse widths. Thresholds for generating ECAPs from Aβ fibers were 100.0 ± 32.3 nC using the SS electrode, and 90.9 ± 42.9 nC using the Injectrode. The ECAP thresholds from the Injectrode were consistent over several hours of stimulation. The rate of recruitment was similar between the Injectrodes and SS electrode and decreased with wider pulse widths.

Results showed that the Injectrode can effectively excite primary afferents when used for DRG stimulation within the range of parameters used for clinical DRG stimulation. The Injectrode can be implanted through minimally invasive techniques while achieving similar neural activation to conventional electrodes, making it an excellent candidate for future DRG stimulation and neuroprosthetic applications.

Learn more here.

Surgical Placement of Customized Abdominal Vagus Nerve Stimulating and Gastrointestinal Serosal Surface Recording Electrodes

Bioelectronic medical approaches to control vagus nerve-to-organ signaling have the potential to treat cardiac, respiratory, gastrointestinal (GI) and metabolic diseases, such as obesity. Unlike cervical vagus nerve stimulation (VNS), abdominal VNS could provide specific therapeutic control of the GI tract without off-target effects on thoracic organs; however, surgical approaches for abdominal VNS electrode placement are not well established.

Moreover, optimal device configurations and additional placement of GI recording electrodes for closed-loop control are largely unknown. The research team designed VNS cuff and GI planar serosal electrodes and tested placement of these devices in laparoscopic surgery in two cadavers. They determined that electrode positioning on the ventral abdominal vagus nerve and gastric antrum was feasible but other sites, such as the duodenum and proximal stomach, were more difficult. The current investigation can guide potential placement and design of VNS cuff and GI electrodes for development of closed-loop GI therapeutic devices.

Learn more here.

Other Contributors to Study #1

Ashley Dalrymple
Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA

Jordyn Ting
Rehab Neural Engineering Labs, University of Pittsburgh, Pittsburgh, PA

Rohit Bose
Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA

James Trevathan
Departments of Biomedical Engineering and Neurological Surgery, University of Wisconsin-Madison, Madison, WI

Stephan Nieuwoudt
Neuronoff Inc., Cleveland, OH

Scott Lempka
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI

Manfred Franke
Neuronoff Inc., Cleveland, OH

Kip Ludwig
Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI

Andrew Shoffstall
Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH

Douglas Weber
Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA

Other Contributors to Study #2

Charles Horn
Department of Medicine, University of Pittsburgh, Pittsburgh, PA

Liane Wong
Micro-Leads Inc., Somerville, MA

Brook Shepard
Department of Medicine, University of Pittsburgh, Pittsburgh, PA

William Gourash
Department of Surgery, University of Pittsburgh, Pittsburgh, PA

Bryan McLaughlin
Micro-Leads Inc., Somerville, MA

Bestoun Ahmed
Department of Surgery, University of Pittsburgh, Pittsburgh, PA