USOO592201.6A

United States Patent (19)11 Patent Number:

5,922,016

Wagner(45) Date of Patent:*Jul. 13, 1999

54). APPARATUS FOR ELECTRIC

4,535,785 8/1985 Van Den Honert et al. ........... 128/746

STIMULATION OF AUDITORY NERVES OFA HUMAN BEING

75

4,577,641
4,858,612
5,119,826

Inventor: Hermann Wagner, Berlin, Germany

5,291,785 3/1994 Downs .......................
5,395,301

73 Assignees: Ingeborg Hochmair, Erwin
Hochmair, both of Axams/Tirol,
Austria* Notice: Thispatentissued onfileda continued
ecutionapplication
under 37 prosCFR
1.53(d), and is subject to the twenty year
patent term provisions of 35 U.S.C.
154(a)(2).

21 Appl. No.: 08/590,567
22 Filed:
Jan. 26, 1996(51) Int. Cl. .................................................. A61F 2/18
52 U.S. Cl. ..................
607/137; 600/559; 128/898
58 Field of Search ................................ 607/55, 56, 136,
607/137; 128/898; 381/312, 60; 600/559
56)References Cited

3/1986 Hochmair et al. ...................... 128/746
8/1989 Stocklin .....................
... 607/136
6/1992 Baart De La Faille ...
128/746... 73/585

3/1995 Russek ...................................... 601/41

Primary Examiner Jack W. Lavinder

Alt
title
M Rr
ttorney, Agent,
Or Firm-Henry
M. Fe1erelsen
57

ABSTRACT

Apparatus for electric Stimulation and diagnostics of audi
tory nerves of a human being, e.g. for determination ofsensation level (SL), most conformable level (MCL) anduncomfortable level (UCL) audibility curves, includes a
Stimulator detachably Secured to a human being for Sendinga signal into a human ear, and an electrode placed within thehuman ear and electrically connected to the Stimulator by anelectric conductor for conducting the Signals from the Stimu
lator into the ear. A control unit is operatively connected to
the Stimulator for instructing the Stimulator as to character
istics of the generated Signals being transmitted to the ear.

U.S. PATENT DOCUMENTS

3,799,146 3/1974 John et al. ............................... 128/2.1

9 Claims, 8 Drawing Sheets

20

19

U.S. Patent

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Sheet 1 of 8

100 TJK TS

02

Off

5,922,016

0G

03

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Sheet 2 of 8

5,922,016

FIG. 2A
UCL - - --MCL - - -

-- -

---

SL 25

224

447

125

250

---

---

- --

500

K

2K

- 10

-20

dB -30
- 40
-50

-60

63

HZ

FIG. 2B
UCL 501
MCL - - SL 89

794
--89

891
--141

999

- 10
LEFT

-20

dB -30
- 40

-50
-60
63

125

250

500

HZ

K

2K

LA

U.S. Patent

Jul. 13, 1999

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Sheet 4 of 8

5,922,016

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Sheet 5 of 8

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U.S. PatentsJul. 13, 1999

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U.S. Patent

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FIG

DISPLAY

Sheet 7 of 8

EA

5,922,016

5,922,016
1
APPARATUS FOR ELECTRICSTIMULATION OF AUDITORY NERVES OFA HUMAN BEINGBACKGROUND OF THE INVENTION

The present invention refers to an apparatus for electric
Stimulation and diagnostics of the auditory nerves of ahuman being, in particular for determination of Sensationlevel, most comfortable level and uncomfortable level

curves of the auditory meatus.
In most deaf people, the transmission of electricalimpulses from the internal ear to the brain is fully functional.
The reason for deafness resides primarily in malfunctions of2
the like, which is situated at the end of an insulated metal rod

with electrical conduction. The metal rod is formed preferably in crank-like manner and is Secured in place by anenveloping plastic body of elastically deformable material
that bears upon the inner wall of the auditory meatus. If
necessary, the metal rod may further be Secured by anadhesive Strip upon the wall Surface of the auditory meatuS.
A placement of the electrode in this manner is particularly
effective to stimulate the auditory nerves.
Preferably, the control unit is of a type to enable a
Selection of the time pattern as well as intensity and fre
quency of the Stimulation Signals for wireleSS transmission,e.g. infrared transmission, to the Stimulator. Thus, the Stimu
lator becomes easy to manipulate while the perSon being

the so-called hair cell which is located within the internal ear 15 examined retains full freedom of movement. The transmitterand responsible for converting mechanical Sound oscillations into electrical neural impulses. In cases of Such defects,
the auditory nerves can be Stimulated directly by electricalimpulses which are generated preferably by an implanted
electronic circuitry via electrodes implanted in or near thecochlea. The Surgical procedure for inserting the implant
into the head is however not only stressful to the patient but
also complex and thus expensive. AS deafness may howeveras well as receiver for wireleSS transmission can be produced
in a simple manner while Still affording the required range
for use with young children.
According to another feature of the present invention, theStimulator is equipped with means for triggering an acoustic
confirmation signal when receiving data from the control
unit to effect the intended stimulation. The generation of theacoustic signal confirms the correctness of the data transalso be the result of a defective transmission of electricalin a simple manner. Preferably, the Stimulator may
impulses, it is indeed conceivable that without evaluation of 25 mission
further include means for triggering acoustic warning Sig
the functionality of the concerned auditory nerves, the nals
in case of malfunction of the intended Stimulation or
implantation may turn out to be of no value.
reception of incorrect data. Thus, the determination ofcharacteristic audibility curves will not be adversely
SUMMARY OF THE INVENTION
effected. Suitably, the triggered warning Signal is differen
It is an object of the present invention to provide an tiated in dependence on the cause for malfunction. This
improved apparatus for electrical Stimulation and diagnos enables the user to pinpoint the error Source as to whether ittics of auditory nerves, which allows determination in is based on apparative malfunction, or possible Screening ofadvance, even in very sensitive and uncooperative patients the receiver diode of the stimulator, or misplaced electrodes,
Such as infants, whether the transmission of Stimuli of the 35 or even on discharged batteries.
auditory nerves is functional or at least Sufficiently func
In accordance with another feature of the present
tional to justify an artificial Stimulation through implantation invention, the Stimulator is provided with a separate opticalof cochlea electrodes.
Signaling device which triggers an optical Signal during
This object, and others which will become apparent transmission of a Stimulation Signal in one of both auditory
hereinafter, are attained in accordance with the present 40 meatuS or in one of both middle ears. Thus, psychologicalinvention by providing a Stimulator which is adapted for conditioning methods as known from pediatric audiometry
detachable Securement to the clothing of a human for are employed for reinforcing the reaction during perception
generating Signals, electrodes placed within the human ear of a Stimulus, with the an additional optical control of theand electrically connected to the Stimulator by an electric Stimulation being accomplished in a simpler manner. The
conductor for conducting the Signals from the Stimulator into 45 optical Signaling device may be a simple toy, Such as a toy
the human ear, and a control unit operatively connected to truck, which is Suitable for infants. During examination, thethe Stimulator for instructing the Stimulator as to character transmission of a Stimulation Signal triggers at the same time
istics of the generated Signals being transmitted.
an optical Signal that draws the attention of the infant. ThisAS the Stimulator for generating the required impulses is reaction provides the operator with a clear and unmistakableeasy to handle, the perSon being examined is inconve 50 Sign that the infant Senses an auditive signal.
nienced only in a very minor way. Suitably, the electrodes
Suitably, the control unit includes a graphic display formay be placed within the auditory meatuS or in the middle illustration of determined audibility curves and associatedC.
numerical values. Thus, characteristic audibility curves can
The electrodes that are placed within the auditory meatuS be monitored during examination, and obviously erroneous
are formed by a body of electrically conducting material 55 values can be corrected by renewed measurements.
Such as e.g. graphite, metal or the like and connected via an Advantageously, the control unit has a terminal for attach
electric conductor to the Stimulator, whereby the conductor ment of a printer to thereby provide the operator with ais Secured in place by an enveloping plastic body of elasti printout of the characteristic audibility curves as determinedcally deformable material which bears upon the inside wall for the auditory meatus of a patient.
of the auditory meatus and may also be used for Sealing the 60
BRIEF DESCRIPTION OF THE DRAWING
auditory meatus. Thus, the Stimulation impulses can betransmitted in a particular effective manner to the auditory
The above and other objects, features and advantages ofnerves while the elastic plastic body Securely retains the the present invention will now be described in more detailelectrode in place within the auditory meatus.
with reference to the accompanying drawing in which:
When being placed in the middle ear, preferably upon the 65 FIG. 1 shows a graphical illustration as well as numericalpromontory, the electrode are provided in form of a body of value illustratior of the pressure level of an audiogram of anelectrically conducting material Such as graphite, metal or auditory nerve Suitable for implantation, commenSurate with

5,922,016
4
preSSure commenSurate with the So-called Sensation level(SL) which is the pressure level of a Sound expressed indecibels above its threshold of audibility for the individual,
apparatus for electric Stimulation of the auditory nerves in and of the uncomfortable level (UCL) of each ear. The
accordance with the present invention;
determination of the characteristic audibility curve of the
FIG. 2a is a graphical illustration of the Sensation level Sensation level is effected by Stimulating the auditory nerve
and uncomfortable level of the right auditory nerve of a deaf at a certain frequency. The intensity of the Stimulation, i.e.
infant, indicating that the examined auditory nerve is most preSSure level, is then gradually increased until the patient
positively identifies an auditive perception. This process islikely unsuitable for implantation;
FIG. 2b is a graphical illustration of the sensation level repeated in a same manner at different frequencies. The
and uncomfortable level of the left auditory nerve of a deaf connection of the family of points determined in this mannerinfant, indicating that the examined auditory nerve is most represents the SL characteristic audibility curve.
The UCL characteristic audibility curve is determined inlikely unsuitable for implantation;
FIG.3 is a Schematic illustration of a Stimulator according 15 a same manner whereby the Sound intensity in decibels forto the present invention as attached to the body of a patient; Stimulating the auditory nerves is increased at each fre
FIG. 4a is a sectional view through the external and quency to Such a degree that the patient experiences aninternal auditory meatus of a human being, illustrating the uncomfortable auditive perception. The connection of theplacement of an electrode of the Stimulating apparatus in the family of points as determined in this manner represents the
UCL characteristic audibility curve.
external auditory meatus,
In FIG. 1, the SL characteristic audibility curve and UCL
FIG. 4b is a sectional view through the external andinternal auditory meatus of a human being, illustrating the audibility curve are plotted by measuring range of Sound
placement of an electrode of the Stimulating apparatus in the intensities in decibels (db) against the Sound frequencies inhertz (Hz) in a frequency range of the Stimulation signals
middle ear;between
63 to 2,000 Hz for an able auditory nerve. The area
FIG. 5 is an exemplified, schematic illustration of the 25
Stimulating apparatus according to the present invention in between the SL audibility curve and the UCL audibility
curve represents the MCL characteristic audibility curve
operative mode,(most comfortable level) which displays those sound inten
FIG. 6a is a schematic illustration of a control unit for use
with the Stimulating apparatus according to the present Sities at different frequencies that are perceived by thepatient as comfortable sound level. The determination of theinvention;
most comfortable level is however relative difficult to ascer
FIG. 6b is a schematic illustration of the back panel of the tain in infants and is of Secondary relevance for evaluating
control unit of FIG. 6a; andthe Suitability of a cochlea implant.
FIG. 7 is a Schematic illustration of a circuitry in form of
FIGS. 2a and 2b depict the SL audibility curve and UCL
a block diagram, showing various components of the Stimu audibility
curve of the right and left auditory nerves of a deaf
35
lator according to the present invention.
infant, and it can be seen that the Suitability of the auditory
DETAILED DESCRIPTION OF PREFERRED
nerves for a cochlea implant is at best doubtful. An auditive
EMBODIMENTS
perception is created in the right auditory meatus only at a
The Sensory perception "hearing is created in a normally very intense Stimulation at low frequencies while frequenhearing human being by the vibrations of the ear drum 40 cies exceeding 250 Hz cannot be perceived at all. The left
through Sound waves that enter the ear. These vibrations are auditory meatus also perceives Sounds only at very low
converted in the internal ear into electrical neural impulses Stimulation frequencies. Based on the pattern of these audi
which are Sent to the brain via the auditory nerves for actual bility curves, the Specialist can ascertain the appropriateneSS
recognition. In cases in which the conversion of the of a cochlea implant and the Surgical procedure.
mechanical oscillations of the ear drum into electrical neural 45
The determination of these audibility curves for deaf
impulses is defective, no acoustic perception takes place. In infants has proven very difficult up to now because of thedeaf human beings which have Such a dysfunctional internal inability to precisely ascertain if and when an auditive
perception has actually occurred. It should be noted in thisear, the conversion of the Sound waves can however beassumed by an electronic circuitry by which the auditory context that persons skilled in the art will understand that thenerves is excited directly with electrical impulses via an 50 Stimulation apparatus according to the present invention
electrode implanted in the cochlea So that the hearing should not be limited to applications with infants but iscapability can at least be partially restored. In order to applicable for diagnostic purposes for perSons of any age
achieve the desired results through the cochlea implant, the group. However, Since the determination of audibility curves
auditory nerves must at least be partially functional in order poses a particular problem when applied for infants, theto effect a transmission of electrical impulses to the brain. 55 following description refers primarily to the use of theSuch cochlea implants are especially Suitable for deaf Stimulation apparatus for infants.
Turning now to FIG. 3, there is shown one embodiment
infants because a Successful implant of a cochlea electrodewith pertaining Sound converter before the infant reaches the of a Stimulating apparatus according to the present
age of Speech acquisition can prevent muteneSS which is a invention, including a Stimulator 1 which is Secured to theconsequence of deafness So that the child can acquire Speech 60 clothing of a child being examined and formed with various
in the infant Stage like healthy children. The Success of Such terminals 15 for connection of conductors. Two conductors
cochlea implants depends upon the functionality and able 7 are respectively routed to the ears of the patient, and one
neSS of the auditory nerve So that a determination of the conductor 7a is connected to a mass electrode 9 that is
effectiveness of the auditory nerve before implantation attached on the skin of the patient, e.g. of the neck.

3
the sensation level (SL), most comfortable level (MCL) anduncomfortable level (UCL), expressed in decibels as afunction of the frequency in hertz (Hz), as determined by an

becomes desirable.

A reliable information about the functional capability of
the auditory nerves requires a determination of the Sound65

As shown in FIG. 4a, the conductors 7 are directed into

the auditory meatus 5 of each ear of the child and terminate
in an electrode 3 in form of a body of electrically conductive

5,922,016
Smaterial Such as e.g. graphite, metal or the like. The elec
trode 3 is preferably of Spherical configuration and embed
ded inside the auditory meatus 5 within an electrolyte 6 near6

panied by an optical Signal. This requires a separate opticalunit which triggers a visual Signal in form of an illuminatinglamp 11 as Soon as a Stimulation impulse is transmitted. Any
the ear drum 16. The inclusion of the electrode 3 in the
toy with illumination, e.g. a toy truck 10, is Suitable aselectrolyte 6 is necessary to establish an effective electrical 5 optical unit for infants. The triggering of a visual signal that
conduction between the electrode 3 and the body mass. A goes hand-in-hand with the generation of a Stimulationpreferred electrolyte 6 is for example 0.9% of saline solu impulse is advantageous because the child realizes that antion. A plastic mass 8 is placed within the external auditory auditive perception is accompanied by a particular light So
meatus 5 of each ear to secure the conductors 7 and thethat each further auditive perception will result in the childelectrode 3 in place and to possibly Seal the inner ear from looking for the illumination of the lamp 11. Even whenoutside.
Shutting down the Stimulation-Synchronous illumination of
FIG. 4b shows a variation in which the stimulator-distal
the light, the child will continue to associate the auditive
perception with the illumination of the lamp 11 of the toy
end of each conductor 7 is widened to include a metal rod
12 and is guided through the ear drum 16 into the middle ear truck 10 anthus automatically look for the lamp 11 so thatcomprised of the auditory ossicles 17 and the Eustachian 15 the operator assigned to the examination for determining theaudibility curves is in a position to ascertain in a particulartube 18. Further shown in FIG. 4b is the cochlea 19 as wellas the nerves 20 and semicircular canals 26 which form the
Simple manner as to whether or not a Stimulation of theinternal ear. The metal rod 12 projects beyond the conductor auditory nerve results in an auditive perception.
7 and terminates in an electrode 4 which bears upon the
In order to check and verify a correct reception in the
promontory within the middle ear 14. The electrode 4 is stimulator 1 of the data being transmitted from the control
made of a body of conductive material Such as e.g. graphite, unit 2, the Stimulator 1 is equipped with means to trigger an
metal or the like and is of spherical configuration. The acoustic confirmation Signal during execution of the desired
placement of the electrodes 4 inside the middle ear is stimulation. In the event the intensity of the stimulation
particular Suitable in difficult cases.
current is reduced compared to the input in the control unit
Advantageously, an adhesive Strip 13 is used for properly 25 2, e.g. due to discharged Voltage Source of the Stimulator 1
positioning the conductor 7 and the metal rod 12 in each ear or interruption of the Stimulation current, or in the event the
before being Secured in place by the plastic mass 8 inserted data transmission is upset for any reason e.g. throughinfrared radiation from a TV remote control or throughin the auditory meatus 5.
The plastic body 8 is suitably made of elastic deformable partial Screening of the receiver diode or transmitter diode,material to Secure the conductor 7 and possibly the metallic the Stimulator 1 triggers a particular warning Signal.
Turning now to FIG. 6a, there is shown a detailedrod 12 in place during movements of the child. A Suitablematerial for the plastic body 8 includes a rapidly and coldly illustration of the control unit 2, including a graphic display
polymerizing plastic material that resembles those materials 25 for illustration of the determined audibility curves andused for Sealing the auditory meatuS from Sound waves. 35 Selected input commands for Verification by the operator.
The electric circuit triggering the Stimulation impulses The operation of the control unit 2 is attained by few input(stimulator 1, electrical conductor 7, electrode 3, electrolyte keys in the following manner:
Before commencing the examination, the type of audibil
6, body of the patient), is closed by the mass electrode 9
which is attached upon the skin of the patient and effects a ity curve (SL, UCL, MCL) to be determined is selected byreturn of the Stimulation currents to the Stimulator 1.
40 Suitably pressing key 20. Actuation of a key 21 situated
The Selection of parameters for the Stimulation, i.e. Sound underneath the key 20 allows a selection of which of both
frequency and Sound intensity as well as time pattern of the electrodes 3, 4 on the left or the right side of the ear should
Stimulation, is inputted into the Stimulator 1 by a control unit output the Stimulation impulses. The desired Sound fre
2 through wireleSS transmission via electromagnetic waves quency is Set by the frequency keys 22, while the Soundin the infrared range, as indicated in FIG. 5. During exami 45 intensities can be modified by the keys 23.
After inputting the required commands, a key 24 (Sonation for determination of characteristic audibility curves,the child which is equipped with the Stimulator 1 can pursue called STIM key) is actuated for transmitting the data to
any desired activity. AS the Stimulator 1 is very Small and is Stimulator 1. After conclusion of the measurements, thefree of any wired connections to the control unit 2, and as the result is illustrated by the graphic display 25. As a printout
electric conductors 7 to the various electrodes 3 or 4 and 9 50 of the test results is typically required, the control unit 2 isare Sufficiently long, the child is afforded complete freedom provided with a terminal 57 (FIG. 6b) for connection of aof movement and the normal behavior is not impeded in any printer (not shown). Thus, all audibility curves as illustrated
by the graphic display 25 are printed also on hard copy.
way.
When, during playing, the child perceives an auditive
FIG. 6b shows the back panel of the control unit 2,
Signal, the activity is interrupted, mostly followed by a 55 illustrating in detail the ON-OFF Switch 50, the printerparticular happy facial expression. A precise observation of terminal 57 and a bore 52 for allowing unobstructed transthe child's reactions can thus be utilized to ascertain the
mission of Signals emitted from the infrared transmitter
threshold of audibility at each frequency and to thereby diode 53 to the stimulator 1 for inputting desired commands.
determine the SL audibility curve. The UCL audibility curve
Turning now to FIG. 7, there is shown an exemplified
can be determined in a similar manner because the facial 60 circuitry in form of a block diagram for the stimulator 1. The
expression and the behavior of the child changes signifi Signal as transmitted from the control unit 2 is received bycantly when the Sound pressure reaches the threshold of an an infrared diode 30 of the stimulator and demodulated byuncomfortable Sound level.
demodulator 31 for input into decoder 32 which translates
When the examination for determination of the audibility the inputted data in a digital data word and checks it for
curves involves particularly uncooperative young children, 65 validity. Subsequently, the data word is stored in register 34.
it has proven Suitable to commence the examination in Such If the received data word is valid, a buzzer 38 is actuated by
a way that the Stimulation of the auditory nerves is accom a respective signal via control logic 33. Preferably, the5,922,016
7

8

placing an electrode within the human ear of a hearing
impaired human being, Said electrode contacting areasin the human ear Susceptive to Stimulation by Said
electric Stimulation Signal;
applying to Said electrode electric Signals having a plu
rality of frequencies and a plurality of intensities forfrom a TV remote control, etc.
eliciting a Sensory response from Said human being as
The stimulator 1 further includes a frequency generator 35
a function of Said frequencies and intensities for deriv
which generates a reference Signal of constant frequency foring characteristic features of audibility curves for Said
input into a counter 36 for splitting the frequency of this 1O
human being;
Signal to thereby generate Signals of frequencies required forcomparing Said Sensory response from Said human being
the stimulation. Bits A, B and C of the digital data word
to audibility curves derived at approximately identicalstored in register 34 control a multiplexer 37 which connects
frequencies of healthy human beings, andthe frequency, commensurate with the value of A, B, C, withpredictingfrom Said comparison the likelihood of Successthe reference Voltage input of a digital/analog converter 15
of a permanent cochlear implant for Said hearing(DAC) 44. The digital input of DAC 44 is connected to theimpaired human being.
bits of the data word which determines the Sound intensity
2.
The
method of claim 1, wherein Said frequencies are in
So that the output of DAC 44 generates an analog signal of a range between
about 60 Hz and 2 kHz.
predetermined amplitude and frequency. This signal ismethod of claim 1, wherein said electrode is placed
amplified by a current output Stage 39 and connected with in 3.theThe
auditory meatus of the human ear.
the electrode 3, 4 of the desired auditory meatus (right or
4. The method of claim 1, wherein said audibility curves
left) by a switch 40.
comprise SL-, MCL- and UCL-audibility curves of the
The current actually flowing through the electrode 3, 4 is auditory meatus of Said human being.
Sensed by a comparator 42 for comparison with a threshold
5. The method of claim 1, wherein placing the electrodevalue 43. If the current flowing through the electrode 3, 4 is 25 further comprises embedding the electrode in an electrolyte
too Small and thus the Sound intensity of the executed body and Sealing the auditory meatus from the outside withstimulation insufficient, buzzer 38 is activated by compara a plastic body.
tor 42 to trigger a respective warning Signal.
6. The method of claim 1, wherein Said electrical signals
While the invention has been illustrated and described as
are transmitted to Said electrode by a detachable Stimulator.
7. The method of claim 1, wherein eliciting a response
embodied in an apparatus for electric Stimulation of auditory
nerves of a human being, it is not intended to be limited to further comprises optically Signaling during transmission of
the details shown Since various modifications and structural
Said Stimulation signals.
changes may be made without departing in any way from the
8. The method of claim 7, wherein said optical signaling
Spirit of the present invention.
is provided by a toy suitable for infants.
What is claimed as new and desired to be protected by 35 9. The method of claim 8, wherein said optical signaling
is provided by a toy truck.
Letters Patent is set forth in the appended claims:
1. Method for testing a response of auditory nerves of a
k
k
k
k
k
human being to an electric Stimulation Signal, comprising:transmission of the data word is executed twice in Series. So

that the Sounding of two Sounds confirms two Successive
correct receptions.
The absence of this signal indicates a failed transmission
e.g. a Screening of the receiver diode, interfering Signals e.g.