Surgery – Surgically implanted vibratory hearing aid
Reexamination Certificate
1999-08-11
2001-06-26
Lacyk, John P. (Department: 3736)
Surgery
Surgically implanted vibratory hearing aid
Reexamination Certificate
active
06251062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an implantable device for treatment of tinnitus which includes an electronic signal generation unit and a power source for power supply of the device.
2. Discussion of Related Art
Many individuals suffer from intermittent or permanent tinnitus which cannot be cured by surgery. Also, to date, there have been no approved drug forms of treatment for tinnitus. However, so-called tinnitus maskers are known, such as disclosed in published PCT application 90/07251. These maskers are small, battery-operated devices which are worn like a hearing aid behind or in the ear and cover (mask) the tinnitus psychoacoustically by artificial sounds which are emitted, for example, via a hearing aid speaker into the auditory canal and which reduce the disturbing tinnitus as far as possible below the threshold of perception. The artificial sounds are often narrowband noise (for example, third octave noise) which in its spectral position and its loudness level can be adjusted via a programming device to enable the maximum possible adaptation to the individual tinnitus situation.
Moreover, recently the so-called “retraining method” has been provided according to which, by combination of a metal training program and presentation of broadband sound (noise) near the hearing threshold, the perceptibility of the tinnitus is supposed to be largely suppressed (see the journal “Hoerakustik” 2/97, pages 26 and 27).
In the two aforementioned methods, technical devices similar to hearing aids can be visibly carried externally on the body in the area of the ear. As a result, these devices stigmatize the wearer and therefore are not willingly worn.
Furthermore, there are currently partially and fully implantable hearing aids for rehabilitation of inner ear impairment such as disclosed in published European patent application Nos. 0 499 940, and 0 831 674, U.S. Pat. Nos. 5,279,292; 5,498,226; 5,624,376; and 5,795,287. In fully implantable systems, the system is not visible, so that in addition to the advantages of high sound quality and the open auditory canal, high acceptance can be assumed.
U.S. Pat. No. 5,795,287 describes an implantable tinnitus masker with direct drive of the middle ear, for example via an electromechanical transducer which is coupled to the ossicle chain. This directly coupled transducer can preferably be a so-called “floating mass transducer” (FMT). This FMT corresponds to the transducer for implantable hearing aids described in U.S. Pat. No. 5,624,376. U.S. Pat. No. 5,795,287 clearly describes the concept of “direct drive” which is explicitly defined as drives including only the types of couplings to the inner ear for purposes of tinnitus masking which are of a mechanical nature. For example, direct drive couplings include direct mechanical converter couplings to one ossicle of the middle ear, such as for example by the FMT converter, and also air gap-coupled electromagnetic converters, such as for example described by Maniglia in U.S. Pat. No. 5,015,225.
All these electromechanical coupling types have the fundamental and serious disadvantage that the surgery for implantation of the entire masker system, or even only the electromechanical transducer, requires fundamentally mechanical manipulations on the ossicle chain of the middle ear or directly at the entry area of the inner ear (oval or round window) and thus involve a considerable risk of inner ear impairment. Furthermore, the necessary surgical opening of an sufficiently large access to the middle ear from the mastoid, for example in the area of the chorda facialis angle (med: “dorsal tympanotomy”, as is necessary in the application of the FMT, can also involve the serious risk of facialis damage and the associated partial paralysis of the face. Furthermore, it cannot always be guaranteed that mechanical coupling will be of a long term, stable nature or that additional clinical damage will not occur, for example, pressure necroses in the area of the middle ear ossicle.
SUMMARY OF THE INVENTION
The aforementioned disadvantages are diminished or completely circumvented by the present invention providing a hermetically gas-tight, biocompatible and implantable electroacoustic transducer in an implantable device for treatment of the tinnitus which is provided with an electronic signal generation unit and a battery for power supply as the sound-delivering output transducer. The electroacoustic transducer is designed such that, after at least partial mastoidectomy, it can be positioned in the mastoid cavity to permit the sound emitted from the electroacoustic transducer to travel via the natural passage of the aditus ad antrum from the mastoid to the tympanic cavity in the area of the middle ear. This sound causes mechanical vibrations of the eardrum which travel via mechanical transmission through the middle ear ossicle to the inner ear or via direct acoustic excitation of the oval or round window of the inner ear. In this manner, these vibrations cause an auditory sensation and thus the desired masking and noiser effect. In the device of the present invention, the implantable output transducer therefore works electroacoustically, not electromechanically.
In another embodiment of the present invention, the electroacoustic transducer includes a preferably metal housing which is hermetically gas-tight on all sides. The housing includes one wall made as a bendable, preferably circular membrane. An electromechanical drive unit is positioned in the housing and coupled to the housing membrane such that output-side mechanical vibrations of the drive unit are mechanically coupled directly from the inside to the housing membrane. In this way, the membrane is excited to bending vibrations which cause sound emission outside the transducer housing. In doing so, the inside electromechanical drive unit may be based on all known converter principles, such as especially piezoelectric, dielectric, electromagnetic, electrodynamic and magnetostrictive.
The transducer housing is preferably cylindrical, especially circular cylindrical, and open on one side. The open side is sealed hermetically gas-tight by the transducer membrane. The transducer housing part and/or the transducer membrane may be produced from a noncorrosive, stainless metal, especially high-quality steel, or from a noncorrosive, stainless and especially physiologically compatible metal, such as titanium, platinum, niobium, tantalum or their alloys.
In one case, when in the implanted state, the electroacoustic transducer is mounted separately from the electronic signal generation unit. Preferably, the transducer housing part is provided with an at least single pole, hermetically gas-tight electrical housing feed-through, wherein the ground potential is on the transducer housing part. The housing feed-through can advantageously be based on a metal-ceramic connection which has been soldered gas-tight. The insulator may include an aluminum oxide ceramic and the electrical feed-through lead may include at least one platinum-iridium wire.
The electromechanical drive unit is preferably a piezo-electric ceramic wafer which can be made circular and which is applied to the inside of the transducer membrane as the electromechanically active element and together with the transducer membrane represents an electromechanically active heteromorph compound element. In this case, as in a bimorph element, the transverse piezoelectric effect is used. However, the partner of the compound in this case does not consist of a second piezoelectrically active element, but of the passive transducer membrane of similar geometry to the piezoelement. The piezoelectric ceramic wafer can be provided on both sides with a very thin, electrically conductive coating used as the electrode surface. The ceramic material may consist of lead zirconate titanate. When an electrical field is applied to the piezoelectric ceramic wafer, the wafer changes its geometry preferably in the radial direction as a result of the transverse piezoeffect. Since lengthening
Implex Aktiengesellschaft Hearing Technology
Lacyk John P.
Nixon & Peabody LLP
Safran David S.
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