Surgery – Diagnostic testing – Structure of body-contacting electrode or electrode inserted...
Reexamination Certificate
1998-11-30
2001-07-17
Yu, Justine R. (Department: 3764)
Surgery
Diagnostic testing
Structure of body-contacting electrode or electrode inserted...
C600S372000, C600S373000
Reexamination Certificate
active
06263225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an apparatus and method for delivering and detecting electrical signals to/from the patient's brain.
In one embodiment, this invention also relates to an apparatus and method for performing ablative surgery on a patient. In particular the invention is concerned with an apparatus and method for performing brain surgery; and more particularly the invention is concerned with an apparatus and method for performing brain surgery by monitoring and selectively inactivating specific regions within the brain. The invention is also concerned with an apparatus and method for delivering therapeutic drugs, and more particularly is concerned with an apparatus and method for delivering therapeutic drug to a specific region within a patient's brain tissues, by monitoring and selectively delivering a drug to the target tissue.
2. Background of the Related Art
Prior to the nineteenth century, physicians and scientists believed the brain was an organ with functional properties distributed equally through its mass. Localization of specific functions within subregions of the brain was first demonstrated in the 1800s, and provided the fundamental conceptual framework for all of modern neuroscience and neurosurgery.
As it became clear that brain subregions served specific functions such as movement of the extremities, and touch sensation, it was also noted that direct electrical stimulation of the surface of these brain regions could cause partial reproduction of these functions. Morgan, J. P., “The first reported case of electrical stimulation of the human brain,”
J. History of Medicine,
January 1982:51-63, 1982; Walker, A. E., “The development of the concept of cerebral localization in the nineteenth century,”
Bull. Hist. Med.,
31:99-121, 1957.
Brain Mapping Studies
The most extensive work on electrical stimulation “mapping” of the human brain surface was carried out over several decades by Dr. Wilder Penfield, a neurosurgeon and physiologist at the Montreal Neurological Institute, mostly during the early to mid-1900s. He made precise observations during cortical stimulation of hundreds of awake patients undergoing brain surgery for intractable epilepsy. Among his many findings, he noted that stimulation of the visual and hearing areas of the brain reproducibly caused the patients to experience visual and auditory phenomena. Penfield, W. et al., “Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation,”
Brain
60:389-443, 1937; Penfield, W. et al., Epilepsy and the Functional Anatomy of the Human Brain, London: Churchill, 1954; Penfield, W. et al., “The brain's record of auditory and visual experience,”
Brain,
86:595-696, 1963. Following the results of early human brain mapping studies, electrical stimulation of sensory brain regions to restore lost function was a logical therapeutic extrapolation. Drs. Brindley and Lewin of the University of Cambridge were the first to reduce the concept to practice by implanting a patient with a visual cortex neural prosthetic device. Brindley, G. S. et al., “The sensations produced by electrical stimulation of the visual cortex,”
J. Physiol.
196:479-493, 1968. Their device consisted of an array of thin, flat electrodes placed on the surface of the visual cortex. The electrodes were remotely controlled with radio signals. A similar system was later tested at the University of Utah by Dr. Dobelle and colleagues. Dobelle, W. H. et al., “Artificial vision for the blind: stimulation of the visual cortex offers hope for a functional prosthesis,”
Science
183:440-444, 1974.
Findings from these early British and American studies were consistent. Patients reliably perceived flashes of light (phosphenes) during periods of electrical stimulation, and simple patterns of phosphenes could be generated by simultaneously activating multiple contacts. While these findings strongly suggested the eventual feasibility of a cortical visual prosthetic device, many important design problems were insurmountable at that time.
Among these were an inability to precisely stimulate very small volumes of brain, the requirement for high stimulation currents to induce phosphenes, and an inability to access the patient's full “visual space” with the large array of surface electrodes used. Additionally, there were no miniature video cameras and small, powerful computers at the time capable of converting visual images into complex electrical stimulation sequences at ultra high speed.
Penetrating Electrodes as Neural Prostheses
The University of Utah has discontinued visual cortex prostheses research. However, the concept has been pursued at NIH where significant additional advances have been made. Their most important discovery to date relates to the use of needle shaped penetrating depth electrodes instead of flat surface stimulating electrodes. Bak, M., et al., “Visual sensations produced by intracortical microstimulation of the human occipital cortex,”
Med. Biol. Eng. Comput.,
28:257-259, 1990. Penetrating electrodes represent a major design improvement. They are placed within the brain tissue itself so there is optimal surface contact with elements of the brain that are targeted for stimulation. As a result, patients perceive visual phosphenes with approximately a thousand-fold less stimulation current than that required when surface electrodes are used. This allows for safe, chronic stimulation of very small discrete volumes of brain.
Additionally, penetrating electrodes transform what was in the past a two dimensional implant-brain interface (flat disks on the surface of the brain) into a three dimensional interface (multiple needle-like electrodes in parallel extending from the surface into the brain substance), which vastly increases the device's access to stimulation targets below the surface. To use a television screen analogy, a two dimensional surface-electrode array may have the potential of generating an image on the “screen” composed of approximately one hundred discreet dots (“pixels”), whereas a three-dimensional array would potentially generate an image with many thousands of dots. The huge potential increase in image resolution would be achieved using a small fraction of the stimulation currents used in the past.
Penetrating electrodes have the potential to markedly increase both image quality and the safety of the stimulation process. Human experimental studies continue at the NIH campus. Extramural NIH funding is also directed at supporting engineering research on penetrating electrodes optimally suited for neural prosthetics applications. The University of Michigan, for example, has made use of computer-chip manufacturing techniques to synthesize exquisitely small electrode arrays. The etched electrical contacts on these devices are so small that the distance separating adjacent contacts can be in the range of 50 micrometers, approximately the diameter of two nerve cell bodies. Drake, K. L. et al., “Performance of planar multisite microprobes in recording extracellular single-unit intracortical activity,”
IEEE Trans. BME,
35:719-732, 1988.
During the 1970s the neural prosthetics group at the University of Utah not only explored the feasibility of a visual cortex neural prosthetic device, but carried out experiments in auditory cortex stimulation as well. Led by Dr. Dobelle, they formed a mobile research group that traveled to surgical centers throughout the United States when suitable experimental subjects were identified. These were patients who required temporal lobe surgery for tumor removal or treatment of intractable epilepsy, and who agreed to participate in the experimental protocol. Dobelle, W. H. et al., “A prosthesis for the deaf based on cortical stimulation,”
Ann. Otol,
82:445-463, 1973.
The primary auditory region of the human brain is buried deep within the Sylvian fissure. It is not visible from the brain surface and its exact location varies slightly from one person to the next
Fleshner & Kim LLP
University of Iowa Research Foundation
Yu Justine R.
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