The sense of hearing in human beings involves the use of hair cells in the cochlea that convert or transduce acoustic signals into auditory nerve impulses. Hearing loss, which may be due to many different causes, is generally of two types: conductive and sensorineural. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded. These sound pathways may be impeded, for example, by damage to the auditory ossicles. Conductive hearing loss may often be overcome through the use of conventional hearing aids that amplify sound so that acoustic signals can reach the hair cells within the cochlea. Some types of conductive hearing loss may also be treated by surgical procedures.
Sensorineural hearing loss, on the other hand, is due to the absence or the destruction of the hair cells in the cochlea which are needed to transduce audio signals into auditory nerve impulses. Thus, many people who suffer from severe to profound sensorineural hearing loss are unable to derive much if any benefit from conventional hearing aid systems. To overcome sensorineural hearing loss, numerous cochlear implant systems, or cochlear prostheses, have been developed. Cochlear implant systems bypass the hair cells in the cochlea by presenting electrical stimulation directly to the auditory nerve fibers. Direct stimulation of the auditory nerve fibers leads to the perception of sound in the brain and at least partial restoration of hearing function.
Cochlear implant systems typically include a cochlear stimulator that is implanted beneath the scalp of a patient. (Note, as used herein, “patient” is used as a synonym for “user” of a cochlear implant system.) An external assembly located external to the patient's scalp includes a microphone to receive sound signals, and sound processing circuitry as well as a battery to power the implanted cochlear stimulator. The external control assembly is also typically used to control and adjust various operational parameters of the implanted cochlear stimulator. An inductive link is used to transmit telemetry signals from the external control assembly to the implanted cochlear stimulator. Power is typically transferred through the scalp to the implanted cochlear stimulator via the inductive link. The external control assembly is often housed within a behind-the-ear (BTE) unit and/or within a carrying case that can be attached to clothing worn by the patient.
Conventional cochlear implant systems are described, e.g., in U.S. Pat. Nos. 4,267,410; 4,532,930; 5,569,307; and 6,842,647, incorporated herein by reference.
Cochlear implant systems use one or more batteries housed within their external assemblies to provide operating power for both the external circuits, e.g., speech processing circuits, and the implanted circuits, e.g., cochlea stimulating circuits. The implanted stimulation electronics have heretofore been powered by transmission from the external module. Such batteries are typically large, bulky, and relatively heavy due to the fact they must have sufficient capacity, and hence be sufficiently large, to provide operating power for extended periods of time. Implanted rechargeable batteries have not heretofore been a viable alternative for powering the implanted module or a cochlear system because there has been no efficient and convenient way to carry out the recharging function. Moreover, heretofore such batteries have degraded in use so that long-term implants would have been limited due to battery loss. Another disadvantage of a system with an implanted rechargeable battery that is recharged by rf telemetry is that the inefficient power transfer causes heating of tissue so that recharging currents must be small and the recharge time long to avoid excessive heating of tissue.
A drawback associated with conventional cochlear implant systems is that they are typically limited to a specific physical configuration, particularly with respect to the implanted components. Once a cochlear implant patient has been fitted with a cochlear implant system, the patient typically has to have the system surgically removed in order to change its physical configuration. Such procedures are invasive, costly, and undesirable.
Yet another drawback associated with conventional cochlear implant systems is that the relatively large external components thereof are readily noticeable to others and lack aesthetic appeal. Moreover, it is difficult to maintain an active lifestyle while wearing the external components because the components may fall off, become damaged, or otherwise malfunction.
It is thus seen that there is a need in the art for a cochlear implant system that overcomes the above-described drawbacks of conventional cochlear implant systems.
A percutaneous cochlear implant system is described in U.S. Pat. No. 4,400,590. However, in use, such system left an opening in the patient's skin through which infection could easily enter. Thus, because infection was a continual risk, use of a percutaneous cochlear implant system of the type described in U.S. Pat. No. 4,400,590 was effectively abandoned over 25 years ago.
Hence, it is further seen that there is a need in the art for a percutaneous cochlear implant system wherein the risk of infection is greatly reduced or eliminated.