A Fully-Integrated Semicircular Canal Processor for an Implantable Vestibular Prosthesis

Published versio

A Neural Implant ASIC for the Restoration of Balance in Individuals with Vestibular Dysfunction

Published versio

A Micropower Tilt Processing Circuit

Accepted versio

Development of a Biomimetic Semicircular Canal with MEMS Sensors to Restore Balance

© 2001-2012 IEEE. A third of adults over the age of 50 suffer from chronic impairment of balance, posture, and/or gaze stability due to partial or complete impairment of the sensory cells in the inner ear responsible for these functions. The consequences of impaired balance organ can be dizziness, social withdrawal, and acceleration of the further functional decline. Despite the significant progress in biomedical sensing technologies, current artificial vestibular systems fail to function in practical situations and in very low frequencies. Herein, we introduced a novel biomechanical device that closely mimics the human vestibular system. A microelectromechanical systems (MEMS) flow sensor was first developed to mimic the vestibular haircell sensors. The sensor was then embedded into a three-dimensional (3D) printed semicircular canal and tested at various angular accelerations in the frequency range from 0.5Hz to 1.5Hz. The miniaturized device embedded into a 3D printed model will respond to mechanical deflections and essentially restore the sense of balance in patients with vestibular dysfunctions. The experimental and simulation studies of semicircular canal presented in this work will pave the way for the development of balance sensory system, which could lead to the design of a low-cost and commercially viable medical device with significant health benefits and economic potential

A Partial-Current-Steering Biphasic Stimulation Driver for Vestibular Prostheses

Published versio

Sensing Movement: Microsensors for Body Motion Measurement

Recognition of body posture and motion is an important physiological function that can keep the body in balance. Man-made motion sensors have also been widely applied for a broad array of biomedical applications including diagnosis of balance disorders and evaluation of energy expenditure. This paper reviews the state-of-the-art sensing components utilized for body motion measurement. The anatomy and working principles of a natural body motion sensor, the human vestibular system, are first described. Various man-made inertial sensors are then elaborated based on their distinctive sensing mechanisms. In particular, both the conventional solid-state motion sensors and the emerging non solid-state motion sensors are depicted. With their lower cost and increased intelligence, man-made motion sensors are expected to play an increasingly important role in biomedical systems for basic research as well as clinical diagnostics

Audio-Vestibular Neurosensory Prosthetics: Origins, Expanding Indications and Future Directions

Approximately one-third of persons over 65 years are affected by disabling hearing loss. It is estimated that the number of people with disabling hearing loss will grow to 630 million by 2030 and maybe over 900 million by 2050. Deafness has significant consequences on many aspects of an individual’s life, including their socioeconomic status, mental and physical well-being, educational and employment opportunities. When congenital or early in the developmental years, deafness results in a delay or loss of language acquisition. Deafness can result from damage or disease anywhere along the auditory pathway. Hearing prosthetic devices help restore hearing and the use of these devices depends on the degree and type of hearing loss. This chapter will give a brief account of the currently available prosthetic hearing solutions

Advances in Microelectronics for Implantable Medical Devices

Implantable medical devices provide therapy to treat numerous health conditions as well as monitoring and diagnosis. Over the years, the development of these devices has seen remarkable progress thanks to tremendous advances in microelectronics, electrode technology, packaging and signal processing techniques. Many of today’s implantable devices use wireless technology to supply power and provide communication. There are many challenges when creating an implantable device. Issues such as reliable and fast bidirectional data communication, efficient power delivery to the implantable circuits, low noise and low power for the recording part of the system, and delivery of safe stimulation to avoid tissue and electrode damage are some of the challenges faced by the microelectronics circuit designer. This paper provides a review of advances in microelectronics over the last decade or so for implantable medical devices and systems. The focus is on neural recording and stimulation circuits suitable for fabrication in modern silicon process technologies and biotelemetry methods for power and data transfer, with particular emphasis on methods employing radio frequency inductive coupling. The paper concludes by highlighting some of the issues that will drive future research in the field

Finite element modeling of residual mechanical hearing function after cochlear implant surgery

Cochlear implant (CI) surgery is one of the most utilized treatments for severe hearing loss. Though CI surgery is proven to improve patients’ quality of life, results are variable as damage to very delicate inner ear tissues can be difficult to avoid. However, even the effects of optimal scala tympani insertions on the mechanics of hearing are not yet fully understood. This project presents two finite element models of the inner ear to study the interrelationship between the mechanical function of the cochlea and the insertion of a cochlear implant electrode, one derived from the chinchilla inner ear and one derived from the rhesus monkey inner ear. These subjects were chosen due to their wide usage in inner ear research as designs of the typical device tend to progress from chinchilla animal studies, to rhesus animal studies, and finally to human trials. Both FE models include a three-chambered cochlea and full vestibular system, rarely seen in prior studies. The procedure used to create these models is low-cost, rapid, and reproducible, and results in a highly detailed model using μMRI imaging as the data source. In the chinchilla model’s unimplanted state, data indicative of the tuning effect of the cochlea closely matched results obtained in In Vivo studies. In its implanted state, the chinchilla model found minimal loss of residual hearing or alteration of the cochlea’s tuning effect regardless of CI insertion angle. Its results suggest that an emphasis should be put on developing CI’s with maximal insertion angles and minimal trauma during insertion. The more detailed rhesus model is presented with its preliminary results and plans for its continued development. In the future, both models can be reused with minimal alteration to study a broad range of phenomena such as vestibulo-cochlear interaction, the results of vestibular implant surgery, and the effects of various pathologies on hearing function

Towards Integrating Vestibular Implant Stimulation of the Semicircular Canals and the Otolith End Organs to Drive Posture, Gait, and Eye-Stabilizing Reflexes

Individuals who suffer from bilateral vestibular hypofunction see an increased risk of falling and a decreased quality of life due to symptoms like imbalance, difficulty keeping their eyes on target during head movement, and difficulty walking. The current standard of care to address these symptoms involves rehabilitation exercises to train the central nervous system to rely on visual and proprioceptive signals to compensate for a loss in vestibular signal. However, no sensory substitution can compensate for the extremely fast ocular and spinal reflexes driven by the vestibular nerves. Decades of research led to the development of multichannel vestibular prostheses designed to electrically stimulate the vestibular nerve endings to provide head movement information from a three-axis motion processing unit. The Johns Hopkins Multichannel Vestibular Implant Early Feasibility Study implanted nine study participants with a unilateral vestibular implant targeting the three semicircular canals. The Johns Hopkins Multichannel Vestibular Implant for clinical use does not incorporate circuitry or hardware to stimulate the remaining two sensory organs of the vestibular system, the otolith end organs, responsible for encoding gravitoinertial accelerations that contribute to ocular and spinal reflexes. Stimulation to these end organs were not the priority because they typically elicit much smaller ocular reflexes and encode slower, low-frequency information that can more easily be compensated by the visual and proprioceptive systems. Additionally, their sensory epithelia encode a wider range of information, so mapping a three-axis accelerometer’s signal to stimulation parameters is not straightforward. The research described in this dissertation first assesses the need for otolith-targeted stimulation by measuring otolith-related vestibulo-spinal reflexes via clinical tests of posture and gait in the Multichannel Vestibular Implant Early Feasibility Study with individuals receiving only semicircular canal-targeted stimulation. In the following chapters, the research expands on previous work done in normally functioning chinchillas to explore otolith-targeted stimulation in a rodent model of bilateral vestibular hypofunction and to understand and optimize the stimulation parameters that will be physiologically relevant and useful to restore otolith-specific information to the vestibular nerve endings. The work described in this dissertation is a step toward a more complete vestibular prosthesis to help restore the otolith-driven reflexes to individuals with profound vestibular loss