A myographic measurement apparatus for direct strength measurement of the orofacial muscles, in particular, the lip and tongue muscles. The apparatus includes a pressure-sensitive probe that is adapted to be placed in engagement with the orofacial muscle being tested. The probe provides a pressure response representative of the muscle strength under test. The probe is coupled to a transducer that converts the probe's pressure response in real time to an electrical signal representative of the force exerted on the probe by the muscle under test. The probe provides a representative pressure reading continuously over a test run of prescribed duration. The electrical signal generated in the test run is sampled and analyzed in real-time to determine a characteristic maximum pressure and hence characteristic maximum muscle strength achieved over the test run. The maximum muscle strength is provided in a form that may be incorporated directly into computerized patient records. The pressure-sensitive probe is provided by a balloon probe that is pneumatically coupled to a transducer. A strength measurement is made by holding the balloon probe against the muscle to be tested and having the patient press against the balloon probe with that muscle. To assist in holding the balloon probe in position a support fixture is provided that includes an anchor member that the patient retains in the mouth, typically gripped by the teeth, and a retaining member that is fixed to the anchor member and is shaped to retain the balloon probe in position against the lip muscle under test. Two illustrative shapes of support fixtures are illustrated for making measurements of the front upper and lower lip muscles and of lateral lip muscle thrust.

BACKGROUND OF THE INVENTION 
The invention relates generally to the field of myography and is more 
particularly directed to apparatus for measuring characteristics of the 
lip and tongue muscles. 
Myography is concerned with the measurement of contractions and relaxations 
of the skeletal muscles. In the diagnosis and treatment of various 
disorders involving the face and mouth, it is often desirable to determine 
the strength of the face and mouth muscles. Such determinations may be 
useful, for example, in assessing and treating certain speech disorders, 
in assessing the need for physical therapy for stroke victims, and for 
tracking progress in recovery from strokes or other injury to the mouth or 
face. Measurement of orofacial muscle strength may also be useful in 
connection with oral surgery, particularly where the musculature is to be 
cut. Measurements prior and post operation, for example, can aid in 
determining an appropriate course of isometric exercise or other physical 
therapy. 
Although muscle strength measurements are recognized as a useful modality 
in diagnosis and assessment, in practice instrumentation for making direct 
measurements of orofacial muscle strength is not widely used. In one 
recent attempt to provide a direct-measurement orofacial instrument, for 
example, the patient "bites down" on a mechanical probe with the lips or 
pushes against the probe with the tongue and the instrument measures the 
strain induced in the probe with a strain gauge. From the strain gauge 
measurement the instrument gives a reading of the mechanical force of the 
patient's bite or push. 
This type of instrument is subject to a number of drawbacks typical of the 
problems encountered with the direct measurement technique. It is 
difficult to obtain reproducibility of results because the measurement 
probes are sensitive to the precise positioning of the probe in the 
patient's mouth, that is, to the precise location at which the patient 
applies the force. In addition, a variety of different probe sizes are 
needed for different mouth sizes, and it then becomes more difficult to 
maintain a common calibration among the varied probe sizes. 
In view of the uncertainty of direct strength measurements by known 
techniques, many practitioners either expect only rough, primarily 
subjective, estimates of muscle strength and consequently do not rely much 
on the strength-measurement modality, or they avoid direct force 
measurements altogether and instead use other techniques for monitoring 
muscle activity such as electromyographic measurements, which measure 
electrical response of the muscles. 
SUMMARY OF THE INVENTION 
The present invention provides myographic measurement apparatus for 
measuring the strength of the orofacial muscles, and in particular, the 
lip and tongue muscles, that provides greater reproducibility of 
measurement under conditions of clinical use, is easy and efficient to 
operate, and is economical to manufacture. 
Briefly, apparatus according to the invention includes a pressure-sensitive 
probe that is adapted to be placed in engagement with the orofacial muscle 
being tested. The probe provides a pressure response representative of the 
muscle strength under test. The probe is coupled to a transducer that 
converts the probe's pressure response in real time to an electrical 
signal representative of the force exerted on the probe by the muscle 
under test. The probe provides a representative pressure reading 
continuously over a test run of prescribed duration. The electrical signal 
generated in the test run is sampled and analyzed in real-time to 
determine a characteristic maximum pressure and hence characteristic 
maximum muscle strength achieved over the test run. The maximum muscle 
strength is provided in a form that may be incorporated directly into 
computerized patient records. 
In the embodiment disclosed here the pressure-sensitive probe is provided 
by a balloon probe that is pneumatically coupled to a transducer. A 
strength measurement is made by holding the balloon probe against the 
muscle to be tested and having the patient press against the balloon probe 
with that muscle. To assist in holding the balloon probe in position a 
support fixture is provided that includes an anchor member that the 
patient retains in the mouth, typically gripped by the teeth, and a 
retaining member that is fixed to the anchor member and is shaped to 
retain the balloon probe in position against the lip muscle under test. 
Two illustrative shapes of support fixtures are discussed below for making 
measurements of the front upper and lower lip muscles and of lateral lip 
muscle thrust. 
Other aspects, advantages, and novel features of the invention are 
described below or will be readily apparent to those skilled in the art 
from the following specifications and drawings of illustrative 
embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
FIGS. 1 and 2 show an illustrative embodiment of a myographic measurement 
apparatus according to the invention. The apparatus includes a 
pressure-sensitive probe shown inserted in a patient's mouth and indicated 
generally by reference numeral 10. Probe 10 provides pressure readings 
relative to the ambient atmospheric pressure that are used for testing the 
strength of the desired muscle. In FIG. 1 the probe is shown inserted in 
the mouth of a patient 11 for making a measurement of the patient's tongue 
muscle strength. The probe is generally placed in engagement with the 
muscle to be tested in a manner to be described more fully below. When the 
patient exerts a force on the probe, the probe produces a pressure 
response representative of the strength of the muscle exerting the force. 
Probe 10 is connected to an instrument housing 12 that contains a 
transducer 13 for converting the pressure response from probe 10 into an 
electrical signal representative of the force exerted by the muscle. 
Housing 12 may include onboard front-end circuitry 14 for preamplifying or 
preliminarily conditioning the signal from transducer 13. Electronic 
circuitry (see FIG. 10), which may or may not be included within housing 
12, receives the representative electrical signal from transducer 13 (or 
from the front-end circuitry 14) and converts it to a digital form to be 
received by a general purpose computer 15 for further processing. The 
circuitry may also provide the system power and receive commands from 
computer 15. As illustrated in FIGS. 1 and 2 the apparatus includes only a 
single probe 10. It may of course also be configured with a plurality of 
probes communicating with a respective plurality of transducers contained 
in a single instrument housing. In this configuration the circuitry will 
also include switching circuitry for selecting amongst the plurality of 
probes. 
Probe 10 is held against the muscle under test, and the muscle exerts a 
force against the probe. In the past, direct force measurements such as 
this have been lacking in their precision and reproducibility of results. 
The problem arises in trying to isolate the force exerted by a particular 
muscle in a particular direction without introducing uncertainties and 
unreproducible factors associated with mechanical linkages or other 
mechanical aspects of the apparatus. According to the present invention 
probe 10 is a pressure-sensitive probe that may be conveniently applied 
directly to the muscle under test at a variety of positions to measure 
muscle strength in different directions and is responsive to the pressure 
rather than to the total force that the muscle exerts. As illustrated in 
FIG. 2 probe 10 may be provided by a balloon 17 that is removably 
connected through coupling 19 of FIG. 3 and air line 18 to instrument 
housing 12. All pressure line connections are easily made by hand using 
standard techniques that give tight seals. A squeeze bulb 21 is provided 
for pumping up balloon 17 with an initial charge of air. Squeeze bulb 21 
is connected to instrument housing 12 by air line 22, which is connected 
within the housing through a lever-action inlet valve 23 and junction 24 
to air line 18 and balloon 17. Bleed valve 25 is provided for bleeding the 
air from balloon 17. The structure and operation of squeeze bulbs is 
familiar, for example, from their use in connection with sphygmomanometers 
for measuring blood pressure and thus need not be disclosed in detail 
here. Transducer 13 is connected to air line 18 through junction 24 for 
communicating pressure variations from the air line to the transducer. 
For accurate measurement it is important that the coupling of balloon 17 to 
air line 18 not leak during a test sequence. A suitably hermetic seal may 
be achieved with the following construction of coupling 19 described with 
reference to FIG. 3. A solid plug 26 is disposed in the neck of balloon 
17. Plug 26 has a central aperture, into which a brass tube 27 is 
press-fit for attachment in standard fashion to air line 18. A collar 28 
of heat-shrinkable plastic is placed around the neck of the balloon and 
plug 26 and heat is applied to the collar causing it to shrink down around 
the neck and hold the balloon securely to plug 26. The outer surface of 
plug 26 may be formed with grooves such as illustrated at 29 in FIG. 3 for 
receiving the deformed skin of balloon 17 and providing an airtight seal. 
To be assured of an airtight seal, it is desirable to apply heat to collar 
28 uniformly around its circumference. Uniform heating is achieved with 
the apparatus of FIG. 4, which comprises a rotatable support member 31 for 
supporting plug 26 and a heating coil 32 for applying heat to 
heat-shrinkable collar 28. Support member 31 includes a base portion 33 
for coupling to a motor (not shown) and a shaft 34 for receiving and 
frictionally engaging brass tube 27. The heating coil is formed with a 
coil diameter permitting the coil to loosely surround the neck of a 
balloon assembled with plug and heat-shrinkable collar in position. In 
operation, a balloon neck is placed over plug 26 and surrounded with an 
unshrunk collar 28. The assembly is mounted on shaft 34 and positioned so 
heating coil 32 surrounds collar 28. Support member 31 together with the 
collar assembly mounted thereon are rotated slowly (e.g., on the order of 
60 revolutions per minute) around a generally horizontal axis as an 
electrical current is applied to coil 32. With this arrangement the coil 
heats collar 28 uniformly, which then shrinks down with uniform tightness 
around the neck of the balloon. Because of the tendency of heated air to 
rise, it has been found that more uniform heating, and hence more uniform 
tightness, has been achieved when shaft 34 and collar 28 are rotated about 
an approximately horizontal axis as opposed to a vertical or substantially 
inclined axis. 
The use of a balloon probe is desirable for a number of reasons. Balloons 
are inexpensive so that it is cost effective merely to discard a balloon 
after use by a patient. This avoids the need for sterilizing the probe 
after each use and thus saves time and the considerable cost of 
sterilization equipment. Operating on pneumatic principles, the balloon 
probe is responsive to very small changes in pressure, may readily be 
deformed to fit into engagement with the muscles of the lips and mouth in 
various configurations, and the resulting measurement is independent of 
the area of contact between the muscle and the balloon and the direction 
in which the muscle force is exerted. While the use of a hydraulic probe 
will also provide a number of these qualities, a pneumatic probe is 
preferred because the measurement will be independent of any hydrostatic 
head associated with the relative height with which a hydraulic probe is 
used and thus there is no need for special circuity or calibration to 
correct for the hydrostatic head. In a pneumatic probe care must be taken 
to account for the compressibility of air or other gas. Boyle's Law for 
gases at constant temperature states that for a given quantity of gas the 
pressure and volume vary inversely. For example, the internal volume of 
the rest of the system cannot exceed the starting volume of the balloon if 
the absolute pressure is to be doubled when the balloon is pressed flat. 
If a greater range of pressure change is desired, the compressible volume 
of air may be reduced by replacing the air in the working volume of the 
transducer and part of the tubing in the instrument housing with a 
non-toxic hydrocarbon compound of low volatility such as mineral oil. No 
error from differential hydrostatic head will be observed if all tests are 
performed with the instrument housing level. 
Although a disposable balloon 17 is desirable for the reasons just 
described, those skilled in the art will recognize that a 
pressure-sensitive pneumatic probe meeting the purposes of the invention 
may be formed in other ways. For example, a stretchable balloon-like 
membrane may be mounted in a probe housing to form a wall of a reservoir 
chamber for air or other gas. The probe housing may be shaped so that the 
membrane presents a convenient surface for engagement with the patient's 
lip or tongue. 
FIG. 5 illustrates the positioning of a balloon probe 17 for making 
measurements of the strength of a patient's tongue muscles. The probe is 
inserted into the patient's mouth typically against the anterior position 
of the hard palate just behind the alveolar ridge. Alternatively, the 
balloon may be placed in a posterior position against the anterior 
incisors with the tongue pressed up against the anterior incisors. On 
command the patient presses against the balloon with the anterior and 
medial positions of the tongue 36 which are the areas having the most 
thrust. The force of the tongue against the balloon is translated into an 
increase in the pneumatic pressure of the air in air line 18, which is 
communicated to transducer 13. The transducer converts this pressure 
increase into an electrical signal for further processing. The 
representative electrical signal thus generated is independent of the 
particular location at which the tongue contacts the probe and does not 
require any correction for mechanical distortions caused by some probes 
such as leverage or other mechanical advantage artificially enhancing or 
diminishing the applied force. 
In making strength measurements of the upper and lower labial regions, the 
balloon probe is used in conjunction with an ancillary supporting fixture 
such as illustrated in FIG. 6. The support fixture of FIG. 6 includes a 
retaining member indicated generally at reference numeral 37 which is 
formed to retain the balloon in position against the pressure exerted by 
the lip muscle being tested. The support fixture of FIG. 6 also includes 
an anchor member indicated generally at reference numeral 38 which is 
formed and sized to be retained conveniently in the mouth for anchoring 
the fixture during the measurement. For the upper and lower labial 
strength measurement retaining member 37 is provided by a curvate or 
angular end portion 39 which defines a generally elongate concavity or 
recess 40 for receiving balloon 17. As illustrated in FIG. 6 anchor member 
38 is generally planar and has a width comparable to the separation of the 
left and right rows of teeth. The support fixture also includes 
replaceable protective pads 41 and 42 on the upper and lower surfaces of 
anchor plate 42. Pads 41 and 42 provide a cushion for gripping by the 
teeth and are preferably removable for cleaning and/or replacement. Pads 
41 and 42 may be provided, for example, by a planar rubberized magnetic 
pad generally conforming to the shape of anchor member 42. When the pads 
41 and 42 are formed of a magnetic material, the support member must of 
course also be formed of a magnetically active material such as Type 430 
stainless steel. The pads are magnetized merely to hold them in position 
on anchor plate 38. 
Measurements of upper and lower labial strength are described with 
reference to FIGS. 7A and 7B. For the upper labial measurement balloon 
probe 17 is inflated and positioned in concavity 40. Anchor member 38 is 
inserted in the patient's mouth so that pad 42 on the underside rests 
against the lower teeth. For the measurement shown in either FIG. 7A or 
7B, the patient's upper lip engages and presses against balloon 17, which 
is held securely in position by retaining member 37. For the measurement 
shown in FIG. 7A the patient's upper lip engages balloon 17 at its upper 
surface and exerts a downward force. For the measurement shown in FIG. 7B 
the patient's upper lip engages balloon 17 at its posterior surface and 
exerts a forward force such as in forming a long "u" sound. For either of 
the measurements the increase in pneumatic pressure within the balloon is 
communicated to transducer 13. To measure the lower labial strength, the 
fixture is inserted in the patient's mouth upside down, i.e., with the 
concavity formed by inverted retaining member 37' on the underside of the 
fixture as shown in phantom in FIGS. 7A and 7B. The patient applies 
pressure with the lower lip to balloon 17'. The measurement then proceeds 
as with the upper labial measurement. 
For lateral strength measurements an appropriate ancillary support fixture 
is illustrated in FIG. 8. The support fixture includes an anchor plate 46 
which is inserted in the patient's mouth and which has a horizontal extent 
sufficient to be gripped and held securely by the teeth along one side of 
the mouth. As in the fixture for the upper and lower labial strength 
measurements, anchor plate 46 is also provided with protective pads 47 on 
the upper and lower surfaces of the anchor plate. This support fixture 
also includes a retaining member indicated generally at reference numeral 
48 formed to retain the balloon in position at the corner of the patient's 
mouth against lateral pressure of the lip muscle being tested. In the 
embodiment of FIG. 8 retaining member 48 comprises a pedestal 49 fixed to 
an edge of anchor plate 46 providing a surface indicated at 50 for 
resisting movement of the balloon and a member 51 mounted on pedestal 49 
also for resisting movement of the balloon. Member 51 is formed with a 
cup-shaped portion 52 for retaining the balloon in position. As 
illustrated in FIG. 8 member 51 has a handle portion 53 by which the 
patient or practitioner may conveniently grasp the fixture to adjust its 
position when in the patient's mouth. To make grasping easier, handle 
portion 53 may be bent away from anchor plate 46. A curved edge of 
cup-shaped portion 52 may be partially cut away as indicated at reference 
numeral 54 to provide an exit passageway for an air line attached to a 
probe nestled in cup-shaped portion 52. 
In use, anchor plate 46 is inserted in the patient's mouth to one side or 
the other and is held in that position by the patient's teeth against 
protective pads 47. Pedestal surface 50 and cup-shaped portion 52 of 
member 51 together with the patient's face at the comer of the mouth form 
a concavity for receiving the balloon. Arranged in this way, the fixture 
helps maintain the balloon in vertical disposition at the corner of the 
mouth so that some portion of the balloon is in contact with the lower lip 
at the comer of the mouth. This is a desirable goal because the lower lip 
is generally the weak portion responsible for droop and thus is typically 
an area one desires to evaluate. FIG. 9 shows a diagrammatic view of the 
top of a patient's head with a balloon 17 mounted in the lateral 
measurement fixture against the side of the patient's mouth. With the 
fixture and balloon mounted in this configuration, the force is applied to 
the balloon by the corner of the lip. 
Electric circuitry for use with the invention is now described with 
reference to FIG. 10. The circuitry may be mounted for example on an 
input/output board installed in general-purpose computer 15. FIG. 10 
illustrates a plurality of transducers 13a, . . . , 13n for supporting a 
plurality of probes in one instrument. The pressure response of an 
individual probe 10 is applied to one of the transducers, say, transducer 
13a, through an appropriate junction or other mixing device. Transducer 
13a converts the pressure response of the probe into an electrical signal 
representative of the muscle activity. Appropriate transducers are well 
known and commercially available. They need not be described in further 
detail here. 
Multiplexer 56 selects the transducer connected to the active probe. The 
raw electrical signal from the selected transducer is applied to an 
analog-to-digital converter 57 (ADC), which provides the raw signal in 
digital form along line 58 to computer 15. These components are standard 
and need not be described in detail here. Control circuitry 59 is 
conventional circuitry for controlling communications with the computer 
and for responding to computer commands to control the ADC, multiplexer, 
and any other diagnostic or supplementary circuitry. General purpose 
inputs 60 and status input channel circuitry 61 are provided for 
diagnostic and maintenance purposes. These may be provided by conventional 
circuitry and do not constitute a part of the present invention. 
In the specific embodiment disclosed here computer 15 includes software 
routines for controlling the ADC subsystem and for implementing data 
collection from the test probes. Computer 15 will also generally include 
other software routines for maintenance and patient data processing tasks 
not forming a part of the present invention. A listing of a specific 
software routine implementing the data collection aspects of the present 
invention is given at the end of this specification. The routine is 
written in the C language and will be readily comprehensible to those 
skilled in the art of C programming given the descriptions provided herein 
and the mnemonics and comments included in the listing. The listing is 
labeled by the C language label PDC.C standing for patient data 
collection. 
The raw representative signal applied to A/D converter 57, and hence the 
signal presented to the computer along line 58, is provided continuously, 
as long as a test continues. The signal will generally rise and fall as 
the patient voluntarily or reflexively exerts more or less thrust against 
the probe and will reach a maximum at the point of maximum muscle thrust. 
The computer repeatedly samples the test signal from ADC 57 at 
30-millisecond intervals and takes the maximum sampled value as 
representative of the maximum strength measurement, which the instrument 
then records as the test result. PDC.C is made up of the following 
principal subroutines, which have the following functions. CaptureData is 
the subroutine that collects a run of data from a test run and returns the 
largest value found. ParseParms checks for command line parameters. 
GetChar gets characters from the computer keyboard. ADCerror displays any 
ADC error. DisplayHelp displays a help screen if an unintelligible command 
line is found. In operation, PDC.C displays a menu of tests to the 
operator who selects the desired test. PDC then runs the selected test. 
To begin the sampling process, CaptureData is fed the keystroke character 
(e.g., 0-9 or A-Z) designating the selected test. CaptureData then calls 
upon ADC driver routines to read the ADC. The ADC driver includes 
subroutines for the following functions: SetupADC sets up the ADC 
subsystem. SetADCChannel selects the desired channel from which the ADC 
reading is to be acquired. ADCbusy determines whether the ADC input 
channel is busy. If the input channel is busy, the computer assumes that 
the ADC is in the process of converting data and is thus not ready. 
ReadADC takes a single reading from the ADC subsystem. More specifically, 
CaptureData repeatedly calls ReadADC, which in turn calls SetADCChannel, 
which sets the desired channel from multiplexer 56. When the channel is 
set, ReadADC initiates the ADC. ReadADC then repeatedly calls ADCbusy to 
determine if the ADC is ready, that is, whether it has finished converting 
test data. When the ADC is ready, PDC then saves a first reading, waits 30 
milliseconds, takes a second reading, saves it, and continues in this 
manner until it has taken 300 readings or until a keystroke Q ends the 
test, whichever occurs first. At this point the read phase is terminated. 
After each reading session PDC selects the largest value and saves it 
internally until it is decided to keep it as a final test value. In the 
code listing illustrated here the final readings are stored with patient 
data by means of the routine SavePData. The remaining readings are saved 
in &lt;test&gt;&lt;date&gt;.tst for possible future use. 
RTC DVR is the real-time clock driver, and TMR DVR is a timer driver. TMR 
DVR provides a clock tick every millisecond, which allows the test to be 
run with one-millisecond accuracy. The other functions and subroutines of 
the listing will be readily understood by those skilled in the art insofar 
as they pertain to the above descriptions. 
The above descriptions and drawings disclose illustrative embodiments of 
the invention. Given the benefit of this disclosure, those skilled in the 
art will appreciate that various modifications, alternate constructions, 
and equivalents may also be employed to achieve the advantages of the 
invention. For example, although pressure-sensitive probe 10 has been 
illustrated here as a pneumatic probe in the form of a balloon, those 
skilled in the art will recognize that other forms of pressure-sensitive 
probes now known or later developed may be substituted for the pneumatic 
probe to serve the same functional and operational purpose. Therefore, the 
invention is not to be limited to the above description and illustrations, 
but is defined by the appended claims. 
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