United States Patent [19]
`Zealear et al.
`
`[75]
`
`[73]
`[21]
`[22]
`[51]
`[52]
`[58]
`
`[56]
`
`[54] SYSTEM AND METHOD FOR EVALUATING
`NEUROLOGICAL FUNCTION
`CONTROLLING MUSCULAR MOVEMENTS
`Inventors: David L. Zealear, 1061 W.
`Hollywood #2A, Chicago, Ill.
`60660; Alan R. Gibson, Phoenix,
`Ariz.
`Assignee: David L. Zealear, Nashville, Tenn.
`Appl. No.: 789,847
`Filed:
`Oct. 18, 1985
`Int. Cl* .............................................. A61B 15/05
`U.S. Cl. .................................... 128/741; 128/643;
`128/774; 128/782
`Field of Search ........ 128/639, 640, 643, 733–734,
`128/741, 744, 774, 777, 782; 73/514; 324/162
`References Cited
`U.S. PATENT DOCUMENTS
`2,580,628 1/1952 Welsch ................................ 128/643
`3,200,814 8/1965 Taylor et al. .
`3,320,947 5/1967 Knoll ................................... 128/741
`3,351,880 11/1967 Wilner ..................................... 338/6
`3,364,929 1/1968 Ide et al.
`... 128/741
`3,534,733 10/1970 Phipps ...........
`... 128/643
`3,557,627 1/1971 Kugath et al. ........................ 73/514
`3,616,698 11/1971 Corey et al. .......................... 73/514
`3,658,054 4/1972 Iberall .
`3,664,329 5/1972 Naylor ...
`... 128/741
`3,783,865 1/1974 Ricketts ............
`... 128/643
`3,785,368 1/1974 McCarthy et al.
`... 128/639
`3,815,427 6/1974 Gladstone .........
`. 73/514 X
`... 128/741
`3,830,226 8/1974 Staub et al. ...
`... 128/741
`3,898,983 8/1975 Elam .........
`4,027,535 6/1977 Swanson ........................... 73/514 X
`4,031,883 6/1977 Febmi et al. ......
`... 128/733 X
`4,044,870 12/1977 Dumitrescu et al. ............... 128/741
`4,088,125 5/1978 Forgione et al. .....
`... 128/741 X
`4,095,551 6/1978 Paul et al. ......................... 73/514 X
`4,166,452 9/1979 Generales, Jr. ...
`... 128/741
`... i2.3/74.
`4,174,706 11/1979 Jankelson et al. ....
`4,198,990 4/1980 Higgins et al. ...
`... 128/782
`4,217,908 8/1980 Staver ...........
`... 128/643
`.... 128/741
`4,236,528 12/1980 Stanec et al. .............
`4,291,705 9/1981 Severinghaus et al. .
`... 128/733
`4,344,441 8/1982 Radke ................................. 128/733
`
`[11] Patent Number:
`[45]. Date of Patent:
`
`4,817,628
`Apr. 4, 1989
`
`4,359,724 11/1982 Zimmerman et al. .......... 128/733 X
`4,387,723 6/1983 Atlee, III et al. ................... 128/734
`(List continued on next page.)
`
`FOREIGN PATENT DOCUMENTS
`0041807 12/1981 European Pat. Off. .
`OTHER PUBLICATIONS
`Fiore et al.; “A Microcomputer-Based Neuromuscular
`Blockade Monitor”, IEEE Trans, on Biomed. Engr., vol.
`BME-28, No. 11, 11–1981, pp. 775–783.
`(List continued on next page.)
`
`Primary Examiner—Kyle L. Howell
`Assistant Examiner—Angela D. Sykes
`Attorney, Agent, or Firm—Banner, Birch, McKie &
`Beckett
`ABSTRACT
`[57]
`A system for evaluating nervous system function of a
`subject including generally an accelerometer sensor, a
`stimulus electrode assembly, and a portable device to
`which the sensor and electrode assembly are connected.
`The sensor measures the magnitude of the (stimulus
`evoked) movement of a body part of the subject along
`at least one axis of three dimensional space. The device
`contains electrical circuits for processing data from the
`sensor, generating stimuli to the electrode assembly,
`and timing both the extraction of sensor information
`and the delivery of stimuli. The sensor has a suction
`chamber for attaching the sensor to the desired body
`part site by static suction. To evaluate the nervous sys
`tem function the magnitude of the monitored sensed
`(acceleration) movement is compared with a control
`value. When the nervous system being evaluated is the
`peripheral nerve of one side of the face, the control
`value can be determined by evoking and measuring
`movement on the opposite side of the face. For this
`embodiment, two pairs of electrodes are attached to a
`headband which holds them simultaneously against
`opposite sides of the face and a switch communicates
`the desired pair with the portable device.
`
`51 Claims, 6 Drawing Sheets
`
`*
`
`
`
`FITBIT, INC. v. LOGANTREE LP
`Ex. 1012 / Page 1 of 19
`
`

`
`4,817,628
`Page 2
`
`
`
`U.S. PATENT DOCUMENTS
`4,437,473 3/1984 Mollan ................................ 128/773
`4,444,205 4/1984 Jackson ............................... 128/782
`4,448,203 5/1984 Williamson et al
`... 128/733
`4,488,445 12/1984 Aske .............
`73/514 X
`4,492,233 1/1985 Petrofsky et al. ................... 128/421
`4,503,863 3/1985 Katims ................................ 128/741
`4,515,168 5/1985 Chester et al. ...................... 128/741
`4,540,002 9/1985 Atlas ................................... 128/734
`4,595,018 6/1986 Rantala ............................... 128/733
`4,653,001 3/1987 Semenon et al. ............... 128/745 X
`OTHER PUBLICATIONS
`Pavlov et al., “Neuromuscular Block Indicator”; Bi
`omed. Engr., vol. 13, No. 4, 3–1980, pp. 205–207.
`“Grass Accelerometer for Parkinsonism”.
`“Kistler Piezo Instrumentation Accelerometers”.
`“WR Medical Electronics Co.—Nerve Monitors”.
`Lance, James W., et al., “Action Tremor and the Cog
`wheel Phenomenon in Parkinson's Disease”, Brain J.
`86:95–110, 1963.
`May, M., Klein, S. R., Blumenthal, F.; Evoked Electro
`myography and Idiopathic Facial Paralysis, Otolaryn
`gol—Head & Neck Surg. 91:678–685, 1983.
`Hughes, G. B., Josey, A.F., Glasscock, M. E., Jackson,
`C. G., Ray, W. A., Sismanis, A.: Clinical electroneurog
`raphy: statistical analysis of controlled measurements in
`twenty-two normal subjects. The Laryngoscope
`19:1834–1846, 1981.
`Cambell, E. D., Hickey, R. P., Nixon, K. H., and A. T.
`Richardson: Value of Nerve-Excitability Measure
`ments in Prognosis of Facial Palsy, Brit. Med. J., 2:7–10,
`1962.
`Burke, R. E. Rudomin, P., and F. E. Zajac, III: The
`Effect of Activation History on Tension Production by
`Individual Muscle Units, Brain Res. 109:515–529, 1976.
`Gantz, B. J., Holliday, M. Gmuer, A. A., and U. Fisch:
`Electroneurographic Evaluation of the Facial Nerve,
`Method and Technical Problems, Ann. Otol. Rhinol.
`Laryngol. 93:394–398, 1984.
`
`Hughes, G. B., Nodar, R. H., and G. W. Williams:
`Analaysis of Test—Retest Variability in Facial Elec
`troneurography, Otolaryngol.—Head & Neck Surg.
`91:290–293, 1983.
`May M., Harvey J. E., Marovits W. F., and M. Stroud:
`The Prognostic Accuracy of the Maximal Stimulation
`Test Compared with that of the Nerve Excitability Test
`in Bell's Palsy, Laryngoscope 81:931–938, 1971.
`Fisch U.: Diagnostic Studies on Idiopathic Facial Palsy,
`In Proceedings of Shambaugh Fifth International Work
`shop on Middle Ear Microsurgery and Fluctuant Hearing
`Loss, Eds. Shambaugh, G. E. and J. J. Shea, The Stroke
`Pub., Inc. Huntsville, Ala., 1977.
`Esslen, E.: Electromyography and Electroneuronogra
`phy, In Facial Nerve Surgery, Ed. U. Fisch, Aesculapius
`Publishing Co., Birmingham, Ala., 1977, (93–100).
`Fisch, U.: Facial Paralysis in Fractures of the Petrous
`Bone, Laryngoscope 84:2141–2154, 1974.
`Fisch, U.: Maximal Nerve Excitability Testing vs Elec
`troneuronography, Arch Otolaryngol, 106:352–357,
`1980.
`Kartush, J. M., Lilly, D. J., Kemink, J. L.; Facial Elec
`troneurography: Clinical and Experimental Investiga
`tions, Otolaryngol–Head & Neck Surg. 93:516–523,
`1983.
`“Experimental Method for Determining the 2-Dimen
`sional Mechanical Properties of Living Human Skin”,
`T. Cook et al., Medical and Biological Engineering and
`Computing, Jul. 1977.
`“Subminiature Three—Directional Accelerometer: An
`Application of Semi-Conductor Strain Gages”, Chiku
`et al., ISA Transactions, vol. 9, No. 2, 1970.
`Fisch, U.: Prognostic Value of Electrical Tests in Acute
`Facial Paralysis, Amer. J. Otol, 5:494–498, 1984.
`Zealear, D. L. and Kurago, K.: Facial Nerve Recording
`from the Eardrum: A Possible Method for Evaluating
`Idiopathic Facial Nerve Paralysis, Otolaryngology Heat
`& Neck Surgery, 93:474–481, Aug. 1985.
`Pansky, B. and E. L. House, Review of Gross Anatomy
`Second Edition, pp. 20–23.
`
`Ex. 1012 / Page 2 of 19
`
`

`
`U.S. Patent
`
`Apr. 4, 1939
`
`Sheet 1 am
`
`4,817,628
`
`Ex.1012/Page3 Of19
`
`Ex. 1012 / Page 3 of 19
`
`

`
`U.S. Patent Apr. 4, 1989
`U.S. Patent
`Apr. 4, 1939
`
`Sheet 2 of 6
`Sheet 2 of 6
`
`4,817,628
`4,817,628
`
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`Ex.1012/Page4 Of19
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`Ex. 1012 / Page 4 of 19
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`

`
`U.S. Patent
`
`Apr. 4, 1989
`
`Sheet 3 of 6
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`4,817,628
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`Ex. 1012 / Page 5 of 19
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`
`
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`
`
`
`

`
`U.S. Patent
`U.S. Patent
`
`Apr. 4, 1989
`Apr. 4, 1989
`
`Sheet 4 of6
`Sheet 4 of 6
`
`4,817,628
`4,817,628
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`Ex. 1012 / Page 6 of 19
`
`
`

`
`U.S. Patent Apr. 4, 1989
`
`Sheet 5 of 6
`
`4,817,628
`
`86
`
`A/G &
`
`INTEGRATE, ETC
`
`
`
`Ex. 1012 / Page 7 of 19
`
`

`
`U.S. Patent Apr. 4, 1989
`
`Sheet 6 of 6
`
`4,817,628
`
`A/G /O
`
`-
`
`32
`
`MANUAL
`tº 54
`
`
`
`DSRMNNRH #
`
`A/G //
`
`
`
`32
`
`MANUAL
`cº)
`
`METER INPUT
`
`
`
`DISCRIMINATOR
`
`FREQUENCY
`TOWOLTAGE
`CONVERTER
`
`
`
`
`
`
`
`
`
`
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`
`
`
`
`Ex. 1012 / Page 8 of 19
`
`

`
`1
`
`SYSTEM AND METHOD FOR EVALUATING
`NEUROLOGICAL FUNCTION CONTROLLING
`MUSCULAR MOVEMENTS
`
`4,817,628
`2
`normal in size suggesting that some nerve fiber signals
`were blocked at the lesion site. Unfortunately, the am
`plitude of a potential that can be recorded from a nerve
`through the skin is very small (approximately ten micro
`volts), so that decreases stemming from signal blocking
`are difficult to detect. This problem is compounded by
`the fact that slight changes in the recording electrode
`position can also cause significant changes in the size of
`the recorded potential. Thus, the method lacks adequate
`sensitivity and accuracy for assessing signal blocking
`that occurs with intensification of a nerve lesion.
`A modification of the method which attempts to give
`a better assessment of signal blocking at a lesion is called
`“evoked electromyography”. Evoked electromyogra
`phy is most commonly utilized for evaluating facial
`nerve function (many physicians call the test “elec
`troneurography” when used in this application). With
`this technique recording electrodes are placed on the
`skin overlying some of the muscle fibers that are con
`trolled by the nerve rather than on the skin overlying
`the nerve. Following activation of the nerve by stimula
`tion, these muscle fibers also become electrically active.
`The compound voltage from muscle fibers or “electro
`myographic potential” can be detected by the recording
`electrodes, amplified, and displayed on an oscilloscope.
`The physician can determine if the recorded response is
`abnormal in either latency (time delay before response)
`or in amplitude, indicating nerve signal slowing or
`blocking, respectively. Unfortunately, this technique
`also has severe limitations with respect to sensitivity
`and accuracy. Although the potential recorded from
`muscle is larger than that recorded from nerve in a
`normal person, the electromyographic potential re
`corded from most patients with nerve signal blocks is
`too small to be accurately measured. The recorded data
`must first be fed into a signal averager in order to obtain
`sufficient signal to noise ratio to measure the response.
`Very few physicians employ this test because of the
`complexity and cost required in using a signal averager.
`The test is also inaccurate. Slight changes in the elec
`trode position produce changes in response amplitude
`or error that are greater than 15% and as large as 100%.
`The method has another limitation in that only those
`nerve fibers controlling muscle fibers in the vicinity of
`the recording electrodes can be assessed for damage.
`Nerve fibers controlling muscle fibers outside this re
`gion may also become damaged by a lesion, but no
`change in the recorded potential will be observed.
`Thus, the method represents a sampling technique and
`can not assess the status of the entire nerve.
`The primary objects of the present invention are to
`provide a method and a device for evaluating the func
`tions of regions of the nervous system, particularly
`peripheral nerves, that control muscular movements,
`using a method and device which is simpler, more sensi
`tive, more accurate, less costly, and safer than prior
`methods and devices.
`Other objects and advantages of the present invention
`will become more apparent to those persons having
`ordinary skill in the art to which the present invention
`pertains from the following description taken in con
`junction with the accompanying drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a perspective view of a system of the present
`invention.
`
`BACKGROUND AND OBJECTS OF THE
`INVENTION
`The present invention relates to devices and methods
`for evaluating neurological function controlling muscu
`lar movements and, more particularly, for evaluating
`10
`peripheral nerve function.
`A peripheral motor nerve is composed of many nerve
`fibers which transmit or conduct electrical signals from
`the central nervous system to the muscles they control.
`15
`Each nerve fiber branches at its termination and
`contacts as many as 200–300 muscle fibers, so that when
`a signal arrives at the terminals of a nerve fiber the
`muscle fibers also become electrically active. Muscle
`fibers are unusual and are distinguished from nerve
`fibers, however, in that once they are electrically active
`20
`they also contract and generate force to move part of
`the body. It is common knowledge that very compli
`cated sequential movements of one or more body parts
`can be produced (such as playing the piano) if the cen
`tral nervous system can recruit the proper combination
`25
`of nerve fibers for each movement in the sequence.
`In many instances central nervous system command
`signals are generated but their conduction down nerve
`fibers is disturbed en route because of a pathological
`change or lesion in the peripheral nerve. In the initial
`stage of a lesion, signal conduction becomes less effi
`cient so that there is a slowing of conduction in the
`nerve fibers affected. If the lesion intensifies, signal
`conduction may become blocked in these nerve fibers.
`Their corresponding muscle fibers can no longer be
`35
`made to contract and the patient has a partial paralysis
`termed “a paresis”. A lesion can intensify to block the
`entire nerve thereby producing a total paralysis.
`In cases where a peripheral nerve lesion is suspected,
`it is important for the physician to test the nerve to
`determine if and to what extent signal conduction has
`been compromised. This information is not only impor
`tant in predicting the outcome in a patient's paralysis
`(i.e. whether the patient will eventually recover from
`the paralysis or not) but also in deciding whether a
`45
`particular form of treatment, such as surgery, should be
`advised. The most common method currently available
`to assess nerve signal conduction is the “nerve conduc
`tion velocity” test. Pairs of stimulus and recording elec
`trodes are placed on the skin overlying the nerve on
`50
`each side of the nerve lesion. When a stimulus is applied
`by passing electricity through the skin, nerve fibers are
`activated and a volley of signals (termed a “compound
`action potential”) is conducted down the nerve through
`the lesion towards the recording electrodes. When the
`55
`action potential reaches the recording electrodes, the
`voltage change detected by the electrodes can be ampli
`fied and displayed on an oscilloscope. The potential
`actually represents a compound voltage of all nerve
`fiber signals that made it through the lesion. The physi
`60
`cian notes on the oscilloscope the time required for the
`potential to travel from the stimulus electrodes to the
`recording electrodes. By measuring the distance be
`tween the electrodes, he can calculate the average con
`duction velocity of the potential and compare it to nor
`65
`mal values to gain some appreciation as to whether the
`lesion caused a slowing of signal conduction. The physi
`cian might also note that the recorded potential is sub
`
`30
`
`Ex. 1012 / Page 9 of 19
`
`

`
`5
`
`20
`
`4,817,628
`3
`4
`part supplied by the nerve; (2) the spring-biased plunger
`FIG. 2 is an enlarged side elevational view of the
`sensor of FIG. 1 having portions thereof broken away.
`37 of the suction syringe 38, which will releasably
`FIG. 3 is an enlarged view of the filament of the
`clamp onto the side of device 24, is depressed and then
`sensor of FIG, 2.
`released to create suction, via polyethylene suction tube
`FIG. 4 is a top view of the filament of FIG. 3.
`40, in the external compartment 42 of sensor 20, thereby
`FIG. 5 is a view similar to FIG. 4 illustrating the
`affixing it to the skin; (3) skin at a specified site overly
`ing the nerve is wiped with a degreasing agent (e.g.
`filament in its flexed condition.
`FIG. 6 is a block diagram illustrating the operation of
`alcohol); (4) a pair of stimulus electrodes 44, 46 is placed
`the system of FIG. 1.
`at the site; (5) the stimulus intensity knob 48 on device
`FIG. 7 is an electrical schematic for the system of 10
`24 is adjusted to a value known to deliver sufficient
`FIG. I.
`current to activate all functional nerve fibers in the
`FIG. 8 is an electrical schematic illustrating a varia
`nerve; (6) the “start” button 50 of device 24 is de
`tion of the sensor circuit portion of the schematic of
`pressed; and (7) the readout on LCD meter 32 is noted
`FIG. 7.
`and recorded. The user compares the value obtained to
`FIG. 9 is a block diagram of a second application of 15
`a normal value for the nerve and can express the value
`the invention of FIG. 1.
`as a percent of normal function if desired. Before de
`FIG. 10 is a block diagram of a third application.
`pressing “start” button 50, if the user makes a connec
`FIG. 11 is a block diagram of a fourth application.
`tion between the “trial integrated force” plug 34 and an
`external device displaying voltage as a function of time
`BRIEF DESCRIPTION OF THE PREFERRED
`(e.g. oscilloscope, strip chart recorder), the integrated
`EMBODIMENT
`force evoked with each stimulus during the test can be
`Since there are problems in measuring the electrical
`monitored. Alternatively, the user can monitor the
`activity of nerve or muscle following nerve stimulation
`force waveform evoked with each stimulus by connect
`as described previously, the present method has been
`ing the “trial force” plug 35 to the external device.
`developed for assessing nerve function by measuring 25
`There is also a “sync out” plug 52 provided to trigger
`the mechanical activity evoked by the stimulation. Fol
`the external device (e.g. oscilloscope) during each stim
`lowing nerve stimulation, a movement or “jerk” of a
`ulus. Finally, the user can specify his own time interval
`body part occurs because of muscular activity. The
`over which a test will be conducted. Instead of depress
`acceleration associated with this movement can be mea
`ing “start” button 50, the user flips the DPDT switch 54
`sured simply by affixing a small accelerometer sensor 30
`on the panel of the device to the “stim manual” position
`with negligible mass to the body part. Since accelera
`to start the test and flips it back to the “stim timed”
`tion varies directly with the force generated in moving
`position to stop the test.
`the body part (as long as its mass remains constant), the
`Device 24 is DC powered and enclosed in a portable
`acceleration measured by the sensor is an index of force.
`box which can be held in one hand, as best shown in
`The force generated, in turn, is directly related to the 35
`FIG. 1. The box has external plugs 58, 60 to make input
`number of nerve fiber signals that reached the muscles
`connections to the sensor 20 and output connections to
`following nerve stimulation. In a patient with a devel
`a pair of stimulus electrodes 44, 46. Two types of stimu
`oping lesion, a decrease will be observed in the mea
`lus electrodes are available. One type is of a standard
`bipolar configuration and can be used for activating
`sured acceleration or force of an evoked movement as
`nerve fiber signals become blocked by the lesion. The 40
`most nerves of the body simply by holding the elec
`percent decrease in force from normal should be, in
`trodes on the skin. The second type shown generally at
`fact, related to the percent of blocked fibers by the
`22 is a novel design and can be used for activating either
`lesion. Slowing of nerve fiber signal conduction can
`the left or right facial nerve. The facial nerve stimulus
`also be determined with this method by measuring the
`electrodes of the second type are novel in two respects.
`latency of the force response following nerve stimula- 45
`First, they are attached to an adjustable headband 66
`tion.
`which provides a convenient means for holding them
`on the skin overlying the facial nerves. These electrodes
`are also particularly useful when performing electromy
`ography of the facial nerve (electroneuography). If the
`method is performed using the standard type of elec
`trodes, the electrodes must be held against the skin.
`Since the technician must use his other hand to hold the
`recording electrodes, he has no free hand to run the
`signal averager, and thus a second technician must be
`present to perform this function. When using the subject
`stimulus electrodes 22 the first technician has a free
`hand to manipulate the averager, so that the aid, or even
`presence, of a second technician is not required. These
`electrodes are also more convenient when performing
`evoked accelerometry, since the electrodes allow both
`hands of the technician to be free for other tasks, inas
`much as it is not necessary to hold the sensor on the
`face.
`The second novel aspect of this electrode design is
`that it incorporates two pairs of electrodes 44, 46 and a
`switch 68 to direct the stimulation to either facial nerve.
`Pairs of felt-lined electrodes 44, 46 are positioned at
`both ends of headband 66, so that when band 66 is put
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`Referring to FIG. 1, the basic components of the 50
`preferred embodiment of the subject invention include
`an accelerometer sensor 20 for measuring evoked
`movement, a stimulus electrode assembly 22 for activat
`ing a nerve, and a portable DC powered device 24.
`Device 24 contains three circuits, as shown in FIGS. 6 55
`and 7—a sensor circuit 26 for processing sensor infor
`mation, a stimulus circuit 28 for delivering stimuli, and
`a timing circuit 30 for timing both the delivery of stim
`uli and extraction of processed sensor information. De
`vice 24 works in either an automatic or manual mode 60
`and test results are read out on its LCD meter 32. Out
`put plugs 34, 35 are also included to provide the option
`for analogue waveforms to be viewed on an oscillo
`scope or to be strip chart recorded.
`The basic steps to determine the largest integrated 65
`force that can be evoked over a time interval of one
`minute are as follows: (1) accelerometer sensor 20 is
`held by placing O' ring 36 at a specified site on the body
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`Ex. 1012 / Page 10 of 19
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`on the head the pairs of electrodes 44, 46 lie against the
`eration will undoubtably be introduced. Adhesives,
`skin overlying the facial nerves as they exit the skull. As
`however, can provide for a secure attachment but once
`illustrated in FIG. 1, each pair of electrodes is posi
`they are applied it is not as easy to relocate the sensor as
`it is when using suction. Adhesives though might be
`tioned so that one electrode is in front of the ear lobe
`useful and possibly preferable to suction in applications
`and the other one is behind it. It is further within the
`scope of the present invention to saturate the electrodes
`where acceleration must be measured over a long per
`iod of time, such as an hour or so, since prolonged
`with saline for effective transfer of current. Stimuli
`generated by device 24 can then be directed to either
`suction can cause damage to skin vessels. In particular,
`pair of electrodes by flicking switch 68. It is thus not
`commercially available rubber disks (not shown) with
`necessary to move a single pair of electrodes from one
`adhesive on both sides and backed with waxed paper
`side of the face to the other. As will be discussed in
`can be used to attach the sensor. One side of the disk can
`greater detail later, the present invention provides that
`be stuck to the sensor and the other side to the skin,
`both the normal and damaged nerve can be tested in a
`after removing the wax paper from each side.
`patient so that their respective nerve functions can be
`Measuring the force generated by the face along one
`compared. It is also within the scope of the invention to
`axis is sufficient to give consistent and accurate informa
`tion regarding the number of incoming nerve fiber sig
`use static suction, as described later for the sensor 20, to
`hold stimulus electrodes 44, 46 against the skin.
`nals. It may be necessary though to use a biaxial or
`As shown in FIG. 2, sensor 20 is a single axis type of
`triaxial accelerometer to accurately assess nerve func
`accelerometer encased in a barrel housing 70 approxi
`tion of other peripheral nerves. In particular, it may be
`mately 5 mm in diameter and 5 mm in length. Sensor 20
`necessary to measure the magnitude of the actual force
`20
`is configured from a filament 72 as shown and such is as
`vector in three-dimensional space. The triaxial type can
`manufactured by Endevco (Pixie transducer, model
`measure the component of the actual force vector
`range 8101,1 U.S. Pat. Nos. 3,351,880 and 3,501,732).
`forces along three orthogonal axes. The magnitude of
`Lead wires 74 are then soldered to one end of the fila
`the actual force vector can be obtained by squaring the
`component forces, summing these squared values, and
`ment 72, a weight 76 of known mass is attached to the
`square-rooting the sum. IC chips are available that
`other end, and the lead wire end anchored inside sensor
`housing 70. When the skin to which the housing 70 is
`square, Sum, and square root, so the present device can
`attached moves, the housing 70 and lead wire end 74 of
`be easily modified to incorporate these chips if it be
`comes necessary to use one of the more sophisticated
`the filament are accelerated. As illustrated in FIGS. 4
`and 5, filament 72 flexes when accelerating the sus
`types of accelerometers in a particular application.
`30
`pended weight 76 on the other end, leading to elonga
`Each of the three types of accelerometers are commer
`tion or compression of the piezoresistive crystal 80.
`cially available.
`Since the crystal distortion causes a change in its resis
`The sensor circuit would be modified as shown in
`tance which is proportional to the distorting force, the
`FIG. 8 where a triaxial accelerometer is used. Note that
`resistance change observed is a measure of the force
`there is no need to rectify after op-amps “A” as before
`which produced the acceleration of weight 76.
`(see FIG. 7), since squaring makes all negative compo
`nent vectors positive before summing. Other possible
`The Sensor filament 72 measures the force of a move
`modifications include changing the values of high pass
`ment as follows. First note that in FIGS. 4 and 5 there
`is an air gap 82 illustrated below piezoresistive crystal
`filters 84 or low pass filters 86 depending upon the
`particular frequency response of the force that is
`80. When the body part moves sensor housing 70 the
`evoked. Another modification which may be necessary
`anchored end of the filament also moves. The move- .
`is to change the time delay before sampling (determined
`ment causes flexion of the filament 72, with much of the
`flexion occurring at its weak point, that is, below air gap
`by timer “0”) in instances where the latency or duration
`82. The flexion, in turn, causes compression of the pi
`of the evoked force vary significantly from that ob
`ezoresistive crystal 80 and a change in its resistance.
`served for the face response. The delay can be changed
`45
`This resistance change is measured and is an index of the
`simply by substituting another value of the 330K resis
`magnitude of the force that produced the movement.
`tor.
`That is, a larger body part force and movement will
`The preferred single axis accelerometer has a flange
`result in a proportionally larger filament flexion, crystal
`90 extending from one end forming a novel open-ended
`compression and measured resistance change. It can
`compartment 42. A rubber O-ring 36 is attached to the
`also be appreciated that the actual amount of flexion
`rim of flange 90. The end of polyethylene tube 40 is
`that occurs with a movement depends upon the size of
`inserted into compartment 42. Accelerometers having
`higher sensitivity and less fragility are commercially
`weight 76 that is attached to the free end of the filament
`72. For a given body part force and movement, the
`available, however, and could be used with this device,
`amount of flexion will increase if a larger weight 76 is
`once equipped with the static suction compartment 42.
`attached. That is, the sensitivity of the filament sensor
`The other end of polyethylene tube 40 is then connected
`can be increased by attaching a larger weight. Weights
`to a spring-loaded syringe 38. When plunger 37 of sy
`of approximately 300 milligrams can be used to obtain
`ringe 38 is depressed compressing the spring, air is
`adequate filament sensitivity. Larger weights could be
`driven out of compartment 42. If O-ring 36 is then
`used, but as can be appreciated there is a limit in the size
`placed on the skin, compartment 42 is closed. When the
`of weight that can be used, since extremely large
`syringe plunger 37 is then released, it springs back creat
`weights make filament 72 more susceptible to breakage.
`ing a vacuum in compartment 42. This method of creat
`To summarize, the filament resistance change that is
`ing static suction is an efficient and simple means for
`measured is proportional to the body part force produc
`attaching accelerometer sensor 20 to the subject's skin
`ing the movement times the mass of the sensor weight.
`at the desired location.
`65
`Methods which do not provide for a secure attach
`Device 24 incorporates three different circuits 26, 28,
`ment of sensor 20 to skin should preferably not be used
`30 as diagrammed in FIG. 7. The first circuit 26 (top of
`(e.g. taping, tieing), because errors in measuring accel
`FIG. 1) processes incoming sensor information. The
`
`50
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`When the circuit is functioning normally, the transistor
`second circuit 28 (bottom of FIG. 7) controls the
`strength of stimuli that are delivered during the test
`turns on with incoming pulses, drawing current from
`period. The third circuit 30 (middle of FIG. 7) is a
`the electrodes through the 10 uR capacitor. That is, the
`timing circuit which controls the duration of the testing
`100k resistor is normally shunted. However, if the tran
`period (the period of time over which stimuli will be
`sistor for some reason becomes damaged and is always
`delivered), the frequency or rate at which square-wave
`turned on, current will only be drawn from the elec
`stimuli will be delivered, and the duration of each
`trodes until the capacitor becomes charged (i.e., for a
`square-wave stimulus.
`second or two). After the capacitor is charged, current
`Referring to sensor circuit 26, when the power is on,
`must pass through the 100K resistor. This resistance
`movements detected by sensor 20 will be continuously
`value is high and limits the current that can be drawn
`decoded by this circuit as analogue voltage signals.
`through the skin to an insignificant level. Second, a
`That is, movements cau