Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-08-17
2001-04-10
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06216040
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an implantable microphone system that is useable with cochlear implants or implantable hearing aids, and more particularly to an implantable microphone system that senses motion of middle ear components without physically touching such elements.
A cochlear implant is an electronic device designed to provide useful hearing and improved communication ability to individuals who are profoundly hearing impaired and unable to achieve speech understanding with hearing aids. Hearing aids (and other types of assistive listening devices) make sounds louder and deliver the amplified sounds to the ear. For individuals with a profound hearing loss, even the most powerful hearing aids may provide little to no benefit.
A profoundly deaf ear is typically one in which the sensory receptors of the inner ear, called hair cells, are damaged or diminished. Making sounds louder or increasing the level of amplification, e.g., through the use of a hearing aid, does not enable such an ear to process sound. In contrast, cochlear implants bypass damaged hair cells and directly stimulate the hearing nerves with electrical current, allowing individuals who are profoundly or totally deaf to receive sound.
In order to better understand how a cochlear implant works, and how the present invention is able to function, it is helpful to have a basic understanding of how the ear normally processes sound. The ear is a remarkable mechanism that consists of three main parts: the outer ear, the middle ear and the inner ear. The outer ear comprises the visible outer portion of the ear and the ear canal. The middle ear includes the eardrum and three tiny bones. The inner ear comprises the fluid-filled snail-shaped cochlea with contains thousands of tiny hair cells.
When the ear is functioning normally, sound waves travel through the air to the outer ear, which collects the sound and directs it through the ear canal to the middle ear. The sound waves strike the eardrum (tympanic membrane) and cause it to vibrate. This vibration creates a chain reaction in the three tiny bones in the middle ear. These three tiny bones are medically termed the malleus, incus and stapes, but are also commonly referred to as the “hammer”, “anvil” and “stirrup”. Motion of these bones, in turn, generates movement of the oval window, which in turn causes movement of the fluid contained in the cochlea.
As indicated above, the cochlea is lined with thousands of tiny sensory receptors commonly referred to as hair cells. As the fluid in the cochlea begins to move, the hair cells convert these mechanical vibrations into electrical impulses and send these signals to the hearing nerves. The electrical energy generated in the hearing nerves is sent to the brain and interpreted as “sound”.
In individuals with a profound hearing loss, the hair cells are damaged or depleted. In these cases, electrical impulses cannot be generated normally. Without these electrical impulses, the hearing nerves cannot carry messages to the brain, and even the loudest of sounds may not be heard.
Although the hair cells in the cochlea may be damaged, there are usually some surviving hearing nerve fibers. A cochlear implant works by bypassing the damaged hair cells and stimulating the surviving hearing nerve fibers with an electrical signal. The stimulated nerve fibers then carry the electrical signals to the brain, where they are interpreted as sound.
Representative cochlear implant devices are described in U.S. Pat. Nos. 4,267,410; 4,428,377; 4,532,930; and 5,603,726, incorporated herein by reference.
Cochlear implants currently use external microphones placed on the body that pick up sound (sense acoustic pressure waves and convert them to electrical signals) and then transmit the electrical signals to a signal processor for amplification, processing and conversion into an electrical stimulation signal (either current or voltage) that is applied to the surviving acoustic nerves located in the cochlea. Such a microphone is, by design, very sensitive, and in order to be sensitive, is by its nature very fragile. Disadvantageously, the external microphone can be damaged if it becomes wet, is dropped or is exposed to extreme conditions frequently encountered in the external environments. These fragile and sensitive microphones also restrict the user's lifestyle and activities. For example, when a user must wear a microphone, he or she is restricted from participation in swimming and other sports, e.g., contact sports, unless the microphone is removed during such activities. If the microphone is removed, however, the user no longer is able to hear. Moreover, many users also find external microphone cosmetically objectionable since they appear out of place and mark the user as “needing assistance”.
It thus evident that improvements are needed in the way users of a cochlear implant, or other hearing aid systems, sense or hear sounds, and more particularly, it is evident that improvements are needed in the microphones used with such systems.
SUMMARY OF THE INVENTION
The present invention addresses the above and other needs by replacing the external microphone commonly used with cochlear implants and other hearing aid systems with an implantable microphone system. Advantageously, such implantable microphone system hears “sound” by sensing motion of middle ear components without having to physically touch such elements.
In broad terms, the invention may be summarized as an implantable microphone system that includes: (1) a sensor for sensing motion of middle ear components without physical contact with middle ear components, wherein the sensor is at least partially implantable within the middle ear; and (2) processing means coupled to the sensor for converting the sensed motion to an electrical output signal. Advantageously, the electrical output signal thus functions as a microphone output signal that varies as a function of acoustic sound waves received through the outer ear and impressed upon the movable middle ear components.
In accordance with one aspect of the invention, the surviving tympanic membrane or other middle ear components is/are used as the diaphragm for a fully implanted microphone. Even though hearing may be lost, most individuals who are characterized as profoundly deaf still have a fully functioning tympanic membrane and middle ear components. The present invention advantageously relies on the response of such fully functioning tympanic membrane or other middle ear components as incoming acoustic pressure waves are received in the outer ear and funneled into the ear canal. The acoustically induced vibrations in any of these moving components in the middle ear are detected using, in one preferred embodiment, a pulsed echo Doppler ultrasound transducer, implanted in the middle ear, and electronic processing means. Other embodiments of the invention may detect the moving components in the middle ear using an optical sensor, or the like.
In operation, the acoustic Doppler transducer exposes a moving component of the middle ear with an ultrasonic signal and receives acoustic reflections from the target anatomy. If the target is moving the received signal will be shifted up or down in frequency by an amount that is proportional to the velocity and displacement of the target movement and the mean velocity of the media filling the separation space between the transducer and the target. This frequency is given by the Doppler equation.
In other embodiments of the invention, an appropriate transducer, e.g., an optical, microwave, infrared, or RF transceiver, similarly exposes one or more moving components of the middle ear with an optical or other electromagnetic signal and receives signal reflections from the target anatomy. When the target anatomy is moving, such movement is detectable in the energy content of the reflected signal.
Thus, it is seen that the implantable microphone system provided by the invention is directed broadly to systems and methods for detecting motion of the functioning middle ear c
Advanced Bionics Corporation
Getzow Scott M.
Gold Bryant R.
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