News Column

Patent Issued for Parylene-Based Microelectrode Array Implant for Spinal Cord Stimulation

August 25, 2014



By a News Reporter-Staff News Editor at Pain & Central Nervous System Week -- According to news reporting originating from Alexandria, Virginia, by NewsRx journalists, a patent by the inventors Tai, Yu-Chong (Pasadena, CA); Nandra, Mandheerej S. (Pasadena, CA); Burdick, Joel W. (Pasadena, CA); Rodger, Damien Craig (South Pasadena, CA); Fong, Andy (Los Angeles, CA); Edgerton, Victor Reggie (Los Angeles, CA); Roy, Roland R. (Playa Vista, CA); Gerasimenko, Yury (Los Angeles, CA); Lavrov, Igor (Rancho Palos Verdes, CA); Harkema, Susan J. (Louisville, KY); Angeli, Claudia A. (Louisville, KY), filed on July 19, 2013, was published online on August 12, 2014 (see also California Institute of Technology).

The assignee for this patent, patent number 8805542, is California Institute of Technology (Pasadena, CA).

Reporters obtained the following quote from the background information supplied by the inventors: "The present invention is directed generally to implantable electrode arrays, and more particularly to implantable electrode arrays used to deliver electrical stimulation to the spinal cord.

"Spinal cord injuries are estimated to afflict over 1.3 million individuals in the United States alone, and paralysis is estimated to affect over 5 million individuals. See 'One Degree of Separation: Paralysis and Spinal Cord Injury in the United States,' Christopher and Dana Reeve Foundation (2009). The debilitating nature of paralysis has a profound effect on quality of life, making even partially effective treatments highly desirable goals for the scientific community.

"Fortunately, experimental research on animals has shown that some level of recovery of locomotion is possible. In particular, epidural spinal cord stimulation has been shown to induce stepping in rats. See R. M. Ichiyama, G. Courtine, Y. P. Gerasimenko, G. J. Yang, R. Brand, I. Lavrov, H. Zhong, R. Roy, V. R. Edgerton, 'Step Training Reinforces Specific Spinal Locomotor Circuitry in Adult Spinal Rats', J. Neuroscience, vol. 29, pp. 7370-7375 (2008); and R. M. Ichiyama, Y. P. Gerasimenko, H. Zhong, R. R. Roy, V. R. Edgerton, 'Hindlimb stepping movements in complete spinal rats induced by epidural spinal cord stimulation,' Neuroscience Letters, vol. 383, issue 3, pp. 339-344 (2005). In these studies, rats were implanted with up to eight wire electrodes. The implanted wire electrodes each extended from a headplug down the neck and to the spinal cord of the rat. During testing, each of the rats was suspended in a jacket such that its hind limbs were positioned on a treadmill. About two weeks after the spinal cord injury, clear stepping patterns were evident when the spinal cord was stimulated. This suggested that the electrical stimulation activated a central pattern generator in the spinal cord.

"The following publications provide examples of work related to electrode arrays used to apply electrical stimulation to the spinal cord: D. C. Rodger, W. Li, A. J. Fong, H. Ameri, E. Meng, J. W. Burdick, R. R. Roy, V. Reggie Edgerton, J. D. Weiland, M. S. Humayun, Y. C. Tai, 'Flexible microfabricated parylene multielectrode arrays for retinal stimulation and spinal cord field modulation,' Proc. 4th International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine and Biology, Okinawa, Japan, pp. 31-34 (2006); K. W. Meacham, R. J. Giuly, L. Guo, S. Hochman, S. P. DeWeerth, 'A lithographically-patterned, elastic multi-electrode array for surface stimulation of the spinal cord', Biomedical Microdevices, vol. 10, no. 2, pp 259-269 (2008); and D. C. Rodger, Wen Li, H. Ameri, A. Ray, J. D. Weiland, M. S. Humayun, Y. C. Tai, 'Flexible Parylene-based Microelectrode Technology for Intraocular Retinal Prostheses,' Proc. IEEE-NEMS 2006, pp 743-746 (2006).

"The publications cited above and other work has led to various designs for high-density electrode arrays to further research, but unfortunately none of these designs has been successfully implanted chronically. A need exists for a chronic implant because chronic implantation is necessary for many applications, such as conducting research, helping a patient move (e.g., step, stand, grip, and the like), improving control of voluntary functions (e.g., voiding the bladder), improving functionality of autonomic processes (e.g., temperature control), and the like. A need also exists for an electrode array assembly configured to more accurately deliver electrical signals to selected locations along the spinal cord. The present application provides these and other advantages as will be apparent from the following detailed description and accompanying figures."

In addition to obtaining background information on this patent, NewsRx editors also obtained the inventors' summary information for this patent: "Embodiments of the invention include an implantable device configured to apply electrical stimulation to a spinal cord of a subject (e.g., a human being or other mammal, such as a rat). The device includes a body portion and a first layer. The body portion has a peripheral portion. Optionally, the peripheral portion includes a frame positioned adjacent the first layer. The frame may be constructed from one or more layers of a substantially electrically nonconductive material (e.g., parylene-A, parylene-C, parylene-AM, parylene-F, parylene-N, parylene-D, and the like). The first layer is constructed from a substantially electrically nonconductive material. In some embodiments, the first layer is constructed from at least one of parylene-A, parylene-C, parylene-AM, parylene-F, parylene-N, and parylene-D. The first layer has a first portion and a second portion. The first portion is positionable alongside the spinal cord and includes a first plurality of openings. For example, the first portion of the first layer may be positioned against a dura of the spinal cord and the device configured to provide electrical stimulation to the dura. The second portion includes a second plurality of openings.

"A plurality of electrodes is positioned inside the peripheral portion and alongside the first portion of the first layer. At least one of the first plurality of openings is adjacent each of the electrodes to provide a pathway through which the electrode may provide electrical stimulation to the spinal cord when the first portion is positioned alongside the spinal cord. In some embodiments, more than one of the first plurality of openings is adjacent each of the plurality of electrodes. In embodiments in which the first portion of the first layer is to be positioned against the dura of the spinal cord, the plurality of electrodes is configured to provide electrical stimulation to the dura.

"A plurality of traces is positioned inside the peripheral portion and alongside the first layer with at least one of the second plurality of openings being adjacent each of the traces to provide a pathway through which the trace may receive electrical stimulation. One or more of the traces is/are connected to each of the electrodes and configured to conduct electrical stimulation received by the one or more of the traces to the electrode. In some embodiments, two of the traces are connected to each of the electrodes. In particular embodiments, the plurality of traces are configured to conduct different electrical stimulation to different ones of the plurality of electrodes. Further, the plurality of traces may be configured to conduct electrical stimulation to fewer than all of the plurality of electrodes.

"In some embodiments, the first layer includes a plurality of grid structures with a different one of the grid structures adjacent each of the plurality of electrodes. Each grid structure defines a plurality of cells. For each of the plurality of electrodes, each of the at least one of the first plurality of openings adjacent the electrode is positioned inside a different one of the cells of the grid structure adjacent the electrode.

"In some embodiments, the body portion includes a second layer. In such embodiments, the plurality of electrodes and the plurality of traces may be positioned between the first and second layers. The first and second layers may each be constructed from at least one of parylene-A, parylene-C, parylene-AM, parylene-F, parylene-N, and parylene-D. Optionally, a flexible outer coating may coat at least a portion of the second layer of the body portion and a portion of the first layer between the first portion of the first layer and the second portion of the first layer. The outer coating may include at least one of a biomedical grade epoxy and a silicone elastomer.

"Embodiments also include a method of constructing an implantable electrode array assembly configured to apply electrical stimulation to the spinal cord of a subject (e.g., a human being or other mammal, such as a rat). The method includes forming a patterned layer of electrically conductive material defining a plurality of electrodes and a plurality of traces, at least one trace being connected to each of the plurality of electrodes. The method also includes forming a first layer of a substantially electrically nonconductive material adjacent the patterned layer. The method also includes forming (e.g., etching) a plurality of first openings and a plurality of second openings in the first layer. The first openings provide access to the plurality of electrodes through the first layer. A different grid defining portion of the first openings is adjacent each of the electrodes. Each grid defining portion exposes a plurality of contacts of the electrode to which the grid defining portion is adjacent. The plurality of second openings provide access to the plurality of traces through the first layer.

"In particular embodiments, the method further includes positioning a sacrificial layer (e.g., a layer of photoresist material) on a substrate (e.g., a silicon wafer), forming a second layer of a substantially electrically nonconductive material on the sacrificial layer, and removing the sacrificial layer to thereby release the second layer from the substrate. In such embodiments, the patterned layer is positioned on the second layer. The patterned layer may be formed on the second layer using a metal deposition technology (e.g., ebeam evaporation). Optionally, the method may include forming a frame layer on the substrate. In such embodiments, the frame layer is underneath the second layer and at least partially defines a frame around the patterned layer. The first and second layers may each be constructed from at least one of parylene-A, parylene-C, parylene-AM, parylene-F, parylene-N, and parylene-D. The first and second layers may be formed from the same material. Optionally, the method may include applying a coating to at least a portion of the second layer and at least a portion of the first layer.

"Another embodiment includes a system that includes a stimulation generator, an implantable electrode array assembly, a baseplate, and a plurality of wires. The stimulation generator is configured to generate electrical stimulation. The implantable electrode array assembly has a proximal end portion connectable to at least one vertebrae and a distal end portion positionable along the spinal cord. The proximal end portion has a plurality of electrical connections to a plurality of electrodes positioned on the distal end portion. The baseplate is configured to be connected to the at least one vertebrae and to connect the assembly to the at least one vertebrae. The plurality of wires is connected to the baseplate and the stimulation generator. The plurality of wires is configured to conduct electrical stimulation generated by the stimulation generator to the baseplate. The baseplate is configured to conduct the electrical stimulation to the plurality of electrical connections of the proximal end portion of the assembly. Optionally, the system may include an overhanging portion connected to the baseplate and positioned to overhang at least a portion of the proximal portion of the assembly to help protect the assembly from external moving tissue."

For more information, see this patent: Tai, Yu-Chong; Nandra, Mandheerej S.; Burdick, Joel W.; Rodger, Damien Craig; Fong, Andy; Edgerton, Victor Reggie; Roy, Roland R.; Gerasimenko, Yury; Lavrov, Igor; Harkema, Susan J.; Angeli, Claudia A.. Parylene-Based Microelectrode Array Implant for Spinal Cord Stimulation. U.S. Patent Number 8805542, filed July 19, 2013, and published online on August 12, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8805542.PN.&OS=PN/8805542RS=PN/8805542

Keywords for this news article include: Paralysis, Spinal Cord, Neuroscience, Central Nervous System, Nervous System Diseases, Neurologic Manifestations, California Institute of Technology.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Pain & Central Nervous System Week


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