(12) United States Patent
`Farquhar
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,206,312 B2
`Jun. 26, 2012
`
`USOO8206312B2
`
`(54) MULTI-CHANNEL STIMULATION
`THRESHOLD DETECTIONALGORTHM
`FOR USE IN NEUROPHYSIOLOGY
`MONITORING
`
`(75) Inventor: Allen Farquhar, San Diego, CA (US)
`
`(73) Assignee: NuVasive, Inc., San Diego, CA (US)
`
`c
`- r
`(*) Notice:
`
`(21) Appl. No.:
`(22) PCT Filed:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 903 days.
`11/994.409
`Sep. 22, 2006
`
`PCT/US2006/037013
`
`(86). PCT No.:
`S371 (c)(1)
`Dec. 31, 2007
`(2), (4) Date:
`(87) PCT Pub. No.: WO2007/038290
`PCT Pub. Date: Apr. 5, 2007
`e a 9
`Prior Publication Data
`US 2008/O167574 A1
`Jul. 10, 2008
`
`(65)
`
`Related U.S. Application Data
`(60) Provisional application No. 60/719,897, filed on Sep.
`22, 2005.
`
`(51) Int. Cl.
`(2006.01)
`A6IB5/05
`(2006.01)
`A61N L/00
`(52) U.S. Cl. ........................................ 600/554; 6O7/116
`(58) Field of Classification Search .................. 600/554,
`600/546-548; 607/39, 40, 48, 61, 66, 68 76,
`607/115-118, 148
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`972,983. A 10/1910 Arthur
`1,328,624 A
`1/1920 Graham
`1,548,184 A
`8, 1925 Cameron
`2,704,064 A
`6, 1955 Fizzell et al.
`2,736,002 A
`2, 1956 Oriel
`2,808,826 A 10, 1957 Reiner et al.
`3,364,929 A
`1/1968 Ide et al.
`3,664,329 A
`5/1972 Naylor
`3.682,162 A
`8, 1972 C
`wwal
`olyer
`3,785,368 A
`1/1974 McCarthy et al.
`3,830,226 A
`8, 1974 Staub et al.
`3,957.036 A
`5, 1976 Normann
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`DE
`
`7, 1999
`299 08 259
`(Continued)
`OTHER PUBLICATIONS
`“Electromyography System.” International Search report from Inter
`national Application No. PCT/US00/32329, Apr. 27, 2001, 9 pages.
`(Continued)
`
`Primary Examiner — Max Hindenburg
`Assistant Examiner — John Pani
`(74) Attorney, Agent, or Firm — NuVasive, Inc.; Rory
`Schermerhorn; Jonathan Spangler
`
`ABSTRACT
`(57)
`The present invention relates generally to an algorithm aimed
`at neurophysiology monitoring, and more particularly to an
`algorithm capable of quickly finding stimulation thresholds
`over multiple channels of a neurophysiology monitoring sys
`tem.
`
`46 Claims, 11 Drawing Sheets
`
`Stimulation Thresholds
`To BeFord
`
`Channel 1
`32
`Channel 2
`
`12
`G
`8S
`Stimulation mA ---
`
`Bracketing
`Bisection
`
`
`
`Channel 2
`
`Bracketing
`Bisection
`
`LEGEND
`# = actual recruit
`E = inferred recruit
`# = actual nonrecruit
`=inferred nonrecruit
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 1
`
`

`

`U.S. PATENT DOCUMENTS
`2E. A.
`Es Sai.
`4.207,897 A
`6/1980 Lloyd et al.
`4,224,949 A
`9, 1980 Scott et al.
`4,226,228 A 10/1980 Shin et al.
`4,235,242 A 11, 1980 Howson et al.
`4,285,347 A
`8, 1981 Hess
`4,291,705 A
`9/1981 Severinghaus et al.
`4,461,300 A
`7/1984 Christensen
`4,515, 168 A
`5, 1985 Chester et al.
`4.519.403. A
`5, 1985 Dickhudt
`4.545,374. A
`10/1985 Jacobson
`45.61445 A
`2, 1985 Berkeletal.
`4,562,832 A
`1/1986 Wilder et al.
`3, 1986 Kambin
`4573,448 A
`4.592,369 A
`6, 1986 Davis et all
`4.595.0 is A
`6/1986 Rantala
`4,616,660 A 10, 1986 Johns
`4,633,889. A
`1/1987 Talalla
`4,658,835. A
`4, 1987 Pohndorf
`4744,371. A
`5/1988 Harris
`4759377. A
`7/1988 Dykstra
`4,784, 150 A 1 1/1988 Voorhies et al.
`4,807,642 A
`2f1989 Brown
`4892.05 A
`1, 1990 Prass
`4926,865 A
`5, 1990 Oman
`4,962,766 A 10/1990 Herzon
`4,964,411 A 10, 1990 Johnson et al.
`5.007.902 A
`4, 1991. Witt
`5,058,602 A 10/1991 Brody
`5081990 A
`1/1992 Deletis
`5,092.344 A
`3, 1992 Lee
`5,125,406 A
`6/1992 Goldstone et al.
`5,127.403 A
`7, 1992 Brownlee
`5,161,533 A 1 1/1992 Prass et al.
`5,196.015 A
`3, 1993 Neubardt
`RE343.90 E
`9, 1993 Culver
`5.255.69 A 10, 1993 Otten
`5,282.468 A
`2/1994 Klepinski
`5,284, 153 A
`2/1994 Raymond et al.
`5,284.154 A
`2/1994 Raymond etal.
`5,299.563 A
`4, 1994 Seton
`5.312.47 A
`5, 1994 Wilk
`5,313,956 A
`5/1994 Knutsson et al.
`5.313.962 A
`5, 1994 Obenchain
`5.337,902 A
`7, 1994 Lemmen
`5,333,618 A
`8, 1994 Lekhtman et al.
`5,375,067 A 12, 1994 Berchin
`5.383,876 A
`1/1995 Nardella
`5.474,558 A
`12/1995 Neubardt
`5.480.440 A
`1/1996 Kambin
`5.482,038 A
`1, 1996 Ruff
`5.484.437 A
`1/1996 Michelson
`5540.235 A
`7, 1996 Wilson
`5.549.656 A
`8, 1996 Reiss
`5.56037) A 10, 1996 CO
`5.566,678 A 10/1996 Evel
`5569248 A 10, 1996 Mathews
`55757s. A
`2, 1996 Cooke
`5.593.429 A
`1, 1997 Ruff
`5.599.279 A
`2f1997 Slotman etal
`5.601608 A
`2/1997 Mouchawar
`5.630.813 A
`5, 1997 Kietlurakis
`5,671,752 A
`9/1997 Sinderby et al.
`5.707.359 A
`1/1998 Bufalini
`57.1307 A
`1/1998 Smits
`5,728,046 A
`3/1998 Mayer et al.
`5.741.253 A
`4, 1998 Michelson
`5,759.159 A
`6, 1998 Masreliez
`5,772,661 A
`6, 1998 Michelson
`5,775,331 A
`7/1998 Raymond et al.
`5,776,144 A
`7/1998 Leysieffer et al.
`5,779,642 A
`7/1998 Nightengale
`5,785,658 A
`7, 1998 Benaron
`5,797,854 A
`8/1998 Hedgecock
`5,814,073. A
`9, 1998 Bonutti
`5,830,151 A 1 1/1998 Hadzic et al.
`5,851,191. A 12/1998 Gozani
`
`US 8,206.312 B2
`Page 2
`
`5,853,373 A 12/1998 Griffith et al.
`5,860,973 A
`1/1999 Michelson
`5,862,314 A
`1/1999 Jeddeloh
`33: A E Real
`5,888.196 A
`3, 1999 S.alig e
`5902.23 A
`5, 1999 Foley etal
`5928,139 A
`T/1999 K. y tal
`5928.15s. A
`7, 1999 R
`5976,094 A 11, 1999 6.Netal
`6,004263 A
`2, 1999 Putzetal.
`6,0985 A
`1, 2000 Ath
`tal
`W .
`.
`.
`a Ca.
`6,027,456 A
`2/2000 Feller et al.
`6,038,469 A
`32000 Karlsson et al.
`E. 20 SE
`COS
`W - W
`6,074,343 A
`6/2000 Nathanson et al.
`6,104,957 A
`8, 2000 Alo et al.
`6,104,960 A
`8/2000 Duysenset al.
`gigs. A
`2.38 Spy
`J. 4 W
`ichelson
`6,126,660 A
`10/2000 Dietz
`6,128,576 A
`10/2000 Nishimoto
`3. A 1938 an et al.
`k - 4
`Ozani et al.
`6,135,965 A 10/2000 Tumer et al.
`6,139,493 A 10/2000 Koros et al.
`3. A 1939: Eai
`66047 A 12/2000 King etal
`J. W. J.
`get al.
`6,181,961 B1
`1/2001 Prass
`6,206,826 B1
`3/2001 Mathews et al.
`6,224,549 B1
`5/2001 Drongelen
`852.
`R 239; Epei et al.
`4. ww.
`Ozani et al.
`85.8 R 658 St.
`4- 4
`rass et al.
`6,306,100 B1 10/2001 Prass
`6,312,392 B1
`11, 2001 Herzon
`6,325,764 B1
`12/2001 Griffith et al.
`38. R 1339, E. 1
`- I w
`elkent et al.
`6,393,325 B1
`5, 2002 Mann et al.
`6.425,859 B1
`7/2002 Foley et al.
`33 R 658 (MA
`I - J.
`an, III et al.
`6,466,817 B1 10/2002 Kaula et al.
`39-43 R
`1399; Matt
`- W
`urner et al.
`6,564,078 B1
`5/2003 Marino et al.
`6,579.244 B2
`6/2003 Goodwin
`6,582,441 B1
`6/2003 He et al.
`6,585,638 B1
`7/2003 Yamamoto
`6,618.626 B2
`9/2003 West et al.
`6,719,692 B2
`4/2004 Kleffner et al.
`6,760,616 B2
`7/2004 Hoey et al.
`6,770,074 B2
`8, 2004 Michelson
`6,796,985 B2
`9/2004 Bolger et al.
`6,819,956 B2 11/2004 DiLorenzo
`6,847,849 B2
`1/2005 Mamo et al.
`6,849,047 B2
`2/2005 Goodwin
`6,855,105 B2
`2/2005 Jackson, III
`6,902,569 B2
`6/2005 Parmer et al.
`6,926,728 B2
`8, 2005 Zucherman et al.
`93. R:
`39.
`land
`W - W
`oey et al.
`7,079,883 B2
`7/2006 Marino et al.
`2.99959 R $39. S.
`J.
`aula et al.
`7,207,949 B2
`4/2007 Miles et al.
`7,258,688 B1
`8/2007 Shah et al.
`7,294,127 B2 11/2007 Leung et al.
`7,310,546 B2 12/2007 Prass
`2001/0039949 A1 11, 2001 Loubser
`2001/0056280 A1 12/2001 Underwood et al.
`2002, 0007129 A1
`1/2002 Marino
`2002/0072686 A1
`6/2002 Hoey et al.
`2002fO161415 A1 10, 2002 Cohen et al.
`2002fO193843 A1 12/2002 Hill et al.
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 2
`
`

`

`US 8,206.312 B2
`Page 3
`
`2/2003 Foley et al.
`2003/0032966 A1
`4/2003 Fey et al.
`2003/00786.18 A1
`6, 2003 Marino
`2003/O105503 A1
`10, 2004 Kelleher et al.
`2004/O199084 A1
`11/2004 Ferree
`2004/0225228 A1
`1/2005 Simonson
`2005.0004593 A1
`1/2005 Miles et al.
`2005, OOO4623 A1
`4/2005 Gharib et al.
`2005.0075578 A1
`4/2005 Simonson et al.
`2005, 0080418 A1
`2005/0085743 A1* 4/2005 Hacker et al. ................. 600,554
`2005, 0119660 A1
`6, 2005 Burlion
`2005, 01824.54 A1
`8, 2005 Gharib et al.
`2005/0256582 A1 11, 2005 Feree
`2006, OO25703 A1
`2/2006 Miles et al.
`2006, OO52828 A1
`3, 2006 Kim et al.
`2006, OO69315 A1
`3, 2006 Miles et al.
`2006/0224078 A1 10/2006 Hoey et al.
`2007, OO16097 A1
`1/2007 Farquhar et al.
`2007/002 1682 A1
`1/2007 Gharib et al. ................. 600,546
`2007. O198062 A1
`8, 2007 Miles et al.
`2007,0293782 A1 12, 2007 Marino
`2008.0015612 A1
`1/2008 Urmey
`2008.00399.14 A1
`2/2008 Cory et al.
`2008/0058606 A1
`3/2008 Miles et al.
`2008, OO64976 A1
`3/2008 Kelleher et al.
`2008, OO64977 A1
`3/2008 Kelleher et al.
`2008/0065178 A1
`3/2008 Kelleher et al.
`2008, 0071191 A1
`3/2008 Kelleher et al.
`
`EP
`EP
`FR
`FR
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`WO
`
`FOREIGN PATENT DOCUMENTS
`O 7593O7
`2, 1997
`O 972 538
`1, 2000
`2795 624
`1, 2001
`2 796846
`2, 2001
`OOf 38574
`T 2000
`OOf 66217
`11, 2000
`OO67645
`11, 2000
`01.03604
`1, 2001
`O1/37728
`5, 2001
`WOO3O26482 A2 * 4/2003
`O3,O37170
`5, 2003
`2004/O12809
`2, 2004
`2005/O13805
`2, 2005
`2006/084193
`8, 2006
`
`OTHER PUBLICATIONS
`"Nerve Proximity and Status Detection System and Method.” Inter
`national Search Report from International Application No. PCT/
`US01/18606, Oct. 18, 2001, 6 pages.
`“Relative Nerve Movement and Status Detection System and
`Method.” International Search Report from International Application
`No. PCT/US01/18579, Jan. 15, 2002, 6 pages.
`“System and Method for Determining Nerve Proximity Direction
`and Pathology During Surgery.” International Search Report from
`International Application No. PCT/US02/22247, Mar. 27, 2003, 4
`pageS.
`“System and Methods for Determining Nerve Direction to a Surgical
`Instrument.” International Search Report from International Appli
`cation No. PCT/US03/02056, Aug. 12, 2003, 5 pages.
`“Systems and Methods for Performing Percutaneous Pedicle Integ
`rity Assessments.” International Search Report from International
`Application No. PCT/US02/35047. Aug. 11, 2003, 5 pages.
`“Systems and Methods for Performing Surgery Procedures and
`Assessments.” International Search Report from International Appli
`cation No. PCT/US02/30617, Jun. 5, 2003, 4 pages.
`“Systems and Methods for Performing Neurophysiologic Assess
`ments. During Spine Surgery.” International Search Report from
`International Application No. PCT/US06/03966, Oct. 23, 2006, 5
`pageS.
`“Multi-Channel Stimulation Threshold Detection Algorithm for Use
`in Neurophysiology Monitoring.” International Search Report from
`International Application No. PCT/US06/37013, Mar. 19, 2007, 10
`pageS.
`Lenke et al., “Triggered Electromyographic Threshold for Accuracy
`of Pedicle Screw Placement.” Spine, 1995, 2004): 1585-1591.
`
`“Brackmann II EMG System.” Medical Electronics, 1999, 4 pages.
`“Neurovision SE Nerve Locator/Monitor'. RLN Systems Inc.
`Operators Manual, 1999, 22 pages.
`“The Brackmann II EMG Monitoring System.” Medical Electronics
`Co. Operator's Manual Version 1.1, 1995, 50 pages.
`“The Nicolet Viking IV.” Nicolet Biomedical Products, 1999, 6
`pageS.
`Anderson et al., “Pedicle screws high electrical resistance: a potential
`source of error with stimulus-evoked EMG.” Spine, Department of
`Orthopaedic Surgery University of Virginia, Jul. 15, 2002, 27 (14):
`1577-1581.
`Bose et al., “Neurophysiologic Monitoring of Spinal Nerve Root
`Function During Instrumented Posterior Lumber Spine Surgery.”
`Spine, 2002, 27(13): 1444-1450.
`Calancie et al., “Stimulus-Evoked EMG Monitoring During
`Transpedicular Lumbosacral Spine Instrumentation' Spine, 1994,
`19(24): 2780-2786.
`Clements et al., “Evoked and Spontaneous Electromyography to
`Evaluate Lumbosacral Pedicle Screw Placement.” Spine, 1996,
`21(5): 600-604.
`Danesh-Clough et al. "The Use of Evoked EMG in Detecting Mis
`placed Thoracolumbar Pedicle Screws.” Spine, Orthopaedic Depart
`ment Dunedin Hospital, Jun. 15, 2001, 26(12): 1313-1316.
`Darden et al., “A Comparison of Impedance and Electromyogram
`Measurements in Detecting the Presence of Pedicle Wall Break
`through.” Spine, Charlotte Spine Center North Carolina, Jan., 15,
`1998, 23(2): 256-262.
`Ebraheim et al., “Anatomic Relations Between the Lumbar Pedicle
`and the Adjacent Neural Structures.” Spine, Department of
`Orthopaedic Surgery Medical College of Ohio, Oct. 15, 1997.
`22(20): 2338-2341.
`Fordetal. “Electrical Characteristics of Peripheral Nerve Stimulators
`Implications for Nerve Localization.” Regional Anesthesia, 1984, 9:
`73-77.
`Glassman et al., “A Prospective Analysis of Intraoperative
`Electromyographic Monitoring of Pedicle Screw Placement With
`Computed Tomographic Scan Confirmation.” Spine, 1995, 20012):
`1375-1379.
`Greenblatt et al., “Needle Nerve Stimulator-Locator: Nerve Blocks
`with a New Instrument for Locating Nerves.” Anesthesia& Analge
`sia, 1962, 41(5): 599–602.
`Haig, “Point of view.” Spine, 2002, 27(24): 2819.
`Haig et al., “The Relation Among Spinal Geometry on MRI,
`Paraspinal Electromyographic Abnormalities, and Age in Persons
`Referred for Electrodiagnostic Testing of Low Back Symptoms.”
`Spine, Department of Physical Medicine and Rehabilitation Univer
`sity of Michigan, Sep. 1, 2002, 27(17): 1918-1925.
`Hollandet al., “Higher Electrical Stimulus Intensities are Required to
`Activate Chronically Compressed Nerve Roots: Implications for
`Intraoperative Electromyographic Pedicle Screw Testing.” Spine,
`Department of Neurology, Johns Hopkins University School of
`Medicine, Jan. 15, 1998, 23(2): 224-227.
`Holland, “Intraoperative Electromyography During Thoracolumbar
`Spinal Surgery.” Spine, 1998, 23(17): 1915-1922.
`Journeeet al., “System for Intra-Operative Monitoring of the Cortical
`Integrity Pedicle During Pedicle Screw Placement in Low Back
`Surgery: Design and Clinical Results.” Sensory and Neuromuscular
`Diagnostic Instrumentation and Data Analysis I, 18th Annual Inter
`national Conference on Engineering in Medicine and Biology Soci
`ety, Amsterdam, 1996, pp. 144-145.
`Maguire et al., “Evaluation of Intrapedicular Screw Position Using
`Intraoperative Evoked Electromyography.” Spine, 1995.20(9): 1068
`1074.
`Martin et al. “Initiation of Erection and Semen Release by Rectal
`Probe Electrostimulation (RPE).” The Journal of Urology, The Wil
`liams& Wilkins Co., 1983, 129: 637-642.
`Minahan et al., “The Effect of Neuromuscular Blockade on Pedicle
`Screw Stimulation Thresholds' Spine, Department of Neurology,
`Johns Hopkins University School of Medicine, Oct. 1, 2000, 25(19):
`2526-2530.
`Pither et al., “The Use of Peripheral Nerve Stimulators for Regional
`Anesthesia: Review of Experimental Characteristics Technique and
`Clinical Applications.” Regional Anesthesia, 1985, 10:49-58.
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 3
`
`

`

`US 8,206.312 B2
`Page 4
`
`Raj et al., “Infraclavicular Brachial Plexus Block—A New
`Approach” Anesthesia and Analgesia, 1973, (52)6: 897-904.
`Raj et al., “The Use of Peripheral Nerve Stimulators for Regional
`Anesthesia.” Clinical Issues in Regional Anesthesia, 1985, 1(4): 1-6.
`Raj et al., “Use of the Nerve Stimulator for Peripheral Blocks.”
`Regional Anesthesia, Apr.-Jun. 1980, pp. 14-21.
`Raymond et al., “The Nerve Seeker: A System for Automated Nerve
`Localization.” Regional Anesthesia, 1992, 17(3): 151-162.
`Shafik, “Cavernous Nerve Simulation through an Extrapelvic
`Subpubic Approach: Role in Penile Erection.” Eur: Urol, 1994, 26:
`98-102.
`Toleikis et al., “The Usefulness of Electrical Stimulation for Assess
`ing Pedicle Screw Replacements.” Journal of Spinal Disorder, 2000,
`13(4): 283-289.
`
`Moed et al., “Insertion of an iliosacral implant in an animal model.”
`Journal of Bone and Joint Surgery, Nov. 1999, 81A(11): 1529-1537.
`“Nim-Response, so advanced... yet so simple.” XoMed, Inc., 1999,
`12 pages.
`Moed et al., “Intraoperative monitoring with stimulus-evoked
`electromyography during placement of iliosacral Screws.” The Jour
`nal of Bone and Joint Surgery, Apr. 1998, 81A(4): 10 pages.
`“New data analyzer combines the functions of six instruments in one
`unit' News Release, Nov. 11, 1987, 3 pages.
`“NuVasive's spine surgery system cleared in the US.” Pharm &
`Medical IndustryWeek, Dec. 10, 2001, 1 page.
`“Risk Capital Funds.” Innovation, Mar. 6, 1990, 172: 3 pages.
`* cited by examiner
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 4
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 1 of 11
`
`US 8,206,312 B2
`
`EMG
`Voltage
`
`FIG. 1
`
`
`
`Stim
`Current
`
`FIG. 2
`
`
`
`Stim
`Current
`
`FIG. 3
`
`Vmax
`
`Time
`
`Single Pulse Stimulation Signal
`200us
`---O-
`
`Time
`
`Multipulse Stimulation Signal
`200us
`50ms
`
`Time
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 5
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 2 of 11
`
`US 8,206.312 B2
`
`Saturation
`
`
`
`EMG
`Voltage
`(Vpp)
`
`Vihresh
`
`thresh
`
`Stimulation Current (mA)
`
`FIG. 4
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 6
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 3 of 11
`
`US 8,206,312 B2
`
`FIG. 5A
`
`Stimulation Threshold
`To Be Found
`
`Stimulation mA -O->
`
`
`
`
`
`
`
`FIG. 5C
`
`
`
`FIG. 5D
`
`First Bracket
`
`EMG Response - NO
`Lower Boundary
`
`EMG Response - YES
`Upper Boundary
`
`Second Bracket
`EMG Response - NO
`Lower Boundary
`
`EMG Response - YES
`Upper Boundary
`
`this step repeated until bracket size is 0.1mA
`
`EMG Response - NO -- |- EMG Response - YES
`Lower Boundary
`Upper Boundary
`O. mA
`
`Switching between response and no response
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 7
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 4 of 11
`
`US 8,206,312 B2
`
`HAS THIS STMULATION
`CURRENT BEEN USED
`RECENTY
`
`
`
`REPORT THE RESULTS OF
`THE PREVIOUS
`STMULATION FOR THIS
`CHANNE
`
`
`
`
`
`RECRUIT: LOWEST
`SIMULATION CURRENT
`THAEVOKEDA
`RESPONSE ON THIS
`CHANNEL
`
`NO RECRUIT: HIGHEST
`SIMULATION CURRENT
`THAT FAILED TO EVOKEA
`RESPONSE ON THIS
`CHANNEL
`
`10
`
`IS RECRUIT
`GREATER THAN
`NO RECRUT
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`SMUATE AT THE
`SPECIFIED CURRENT AND BETWEEN
`RepORT THE RESULTS
`FORTHS CHANNE
`
`
`
`STHE SPECIFED STEM
`CURRENTOWER OR
`HIGHER THAN RECRUIT
`AND NO RECRUIT
`
`HIGHER
`
`12
`
`REPORT NO RECRUIT
`FORTHS CHANNA
`THE PRESENT CURRENT
`
`REPORTRECRUIT
`FORTHS CHANNELAT
`THE PRESENT CURRENT
`
`16
`
`FIG. 6
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 8
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 5 of 11
`
`US 8,206,312 B2
`
`FI G. 7 A Channel 1
`Channel 2
`
`
`
`FIG. 7B
`
`Channel 1
`Bracketing
`Bisection
`
`Stimulation Thresholds
`To Be Found
`12.5
`Q
`
`8.5
`
`Stimulation mA -i-H)
`
`o
`H- Initial Bracket -
`s
`16
`H Bracket 2
`12
`Bracket 3
`14
`F-Final Bracket
`
`mA
`
`FIG. 7C
`
`Channel 2
`
`Bracketing 1 2
`Bisection
`
`H - Initial Bracket -
`S
`1C5
`H-Bracket 2 -
`E.
`Bracket 3 ill- 12
`
`Final Bracket
`
`i
`
`10
`
`9
`
`LEGEND
`
`actual recruit
`inferred recruit
`actual nonrecruit
`inferred nonrecruit
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 9
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 6 of 11
`
`US 8,206,312 B2
`
`
`
`
`
`
`
`
`
`NITIAL THRESHOLD
`
`YES
`
`
`
`22
`
`CONFIRM
`PREVIOUS
`THRES HOLD
`
`HRESHOLD FOUND
`?
`
`
`
`BRACKET
`
`BSECT
`
`28
`
`
`
`REPORT
`THRESHOD
`
`24
`
`FIG. 8
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 10
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 7 of 11
`
`US 8,206.312 B2
`
`
`
`Confirmation Step
`
`Previously determined
`thresh
`
`le
`
`Confirmation Stimulation
`EMG Response - NO
`
`|- Confirmation Stimulation
`EMG Response - YES
`0.1 mA
`
`FIG. 9
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 11
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 8 of 11
`
`US 8,206,312 B2
`
`
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 12
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 9 of 11
`
`US 8,206,312 B2
`
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`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 13
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 13
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 10 of 11
`
`US 8,206,312 B2
`
`
`
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`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 14
`
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`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 14
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Jun. 26, 2012
`
`Sheet 11 of 11
`
`US 8,206,312 B2
`
`
`
`@
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 15
`
`

`

`US 8,206,312 B2
`
`1.
`MULT-CHANNEL STIMULATION
`THRESHOLD DETECTIONALGORTHM
`FOR USE IN NEUROPHYSIOLOGY
`MONITORING
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is an international patent application
`claiming the benefit of priority from commonly owned and
`U.S. Provisional Patent Application Ser. No. 60/719,897,
`entitled "Multi-Channel Stimulation Threshold Detection
`Algorithm for Use With Neurophysiology Monitoring Sys
`tems.” and filed on Sep. 22, 2005.
`
`BACKGROUND OF THE INVENTION
`
`1. Field
`The present invention relates generally to an algorithm
`aimed at neurophysiology monitoring, and more particularly
`to an algorithm capable of quickly finding stimulation thresh
`olds over multiple channels of a neurophysiology monitoring
`system.
`2. Background
`The risk of neurological impairment is a prime concern
`when performing Surgical procedures in close proximity to
`the spine or nerves. To combat this risk, Surgeons are increas
`ingly relying on neurophysiology monitoring techniques to
`monitor nerves and alert them to potential impairment during
`a Surgical procedure. Often times effective nerve monitoring
`requires monitoring neurophysiologic results over a multi
`tude of channels. While this is generally advantageous, it may
`have the negative effect of increasing the time required to
`complete nerve monitoring and therefore increasing the over
`all Surgery time as well, which in turn increases the costs and
`risks associated with the Surgery. Based on the foregoing, a
`need exists for an improved means of neurophysiology moni
`toring, and in particular a needs exists for a means to reduce
`the time required to monitor neurophysiologic results over a
`multitude of channels. The present invention is aimed at
`addressing these needs.
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`SUMMARY OF THE INVENTION
`
`45
`
`50
`
`The present invention endows Surgeons with valuable
`information that allows for the efficient assessment of risk to
`neural tissue before, during, and/or after a Surgical procedure.
`This is accomplished by quickly and accurately determining
`a stimulation threshold for neural tissue and relaying that
`information to the Surgeon in a simple comprehensible fash
`ion. Stimulation thresholds are determined by electrically
`stimulating nerve tissue and analyzing resulting muscle activ
`ity relative to determine the stimulation current level at which
`nerve tissue depolarizes. To make stimulation threshold
`determinations, muscle activity may be monitored by mea
`55
`Suring electrical signals associated with muscle contraction,
`called electromyography (“EMG'). EMG responses can be
`characterized by a peak-to-peak voltage of VV-V.
`Characteristics of the electrical stimulation signal used may
`vary depending upon several factors, including the particular
`nerve assessment performed, the spinal target level, the type
`of neural tissue stimulated (e.g. nerve root, spinal cord, brain,
`etc. . . ) among others.
`A basic premise underlying the stimulation threshold tech
`nique is that nerves have a characteristic threshold current
`level (I) at which they will depolarize and cause a sig
`nificant EMG response. A significant EMG response may be
`
`60
`
`65
`
`2
`defined as having a V greater than a predetermined thresh
`old Voltage (V). By way of example only, the V, may
`be selected from a range including 20 V-100 uV. Stimulation
`with a current below the threshold level, I
`will not evoke
`a significant EMG response, while stimulation with a current
`at or above the threshold level will evoke a significant EMG
`response. This relationship between the stimulation current
`and the EMG response may be represented via a “recruitment
`curve.” When stimulation does not evoke a significant EMG
`response (represented in the onset region) the stimulation
`current is said to have not “recruited.” When stimulation does
`evoke a significant EMG response (represented in the linear
`and Saturation regions) the stimulation current is said to have
`“recruited. It
`is the lowest stimulation current that
`recruits (evokes a significant EMG response).
`The algorithm described herein may considerably reduce
`the number of stimulations, and thus time, required to deter
`mine I, particularly for a number of channels, over the
`course of a procedure. The basic method for finding I,
`utilizes a bracketing method and a bisection method. The
`bracketing method quickly finds a range (bracket) of Stimu
`lation currents that must contain I, and the bisection
`method narrows the bracket until I, is known within a
`specified accuracy.
`The bracketing method adjusts the stimulation current as
`follows. Stimulation begins at a minimum stimulation cur
`rent. Each Subsequent stimulation is delivered at a current
`level double that of the preceding current. This doubling
`continues until a stimulation current results in an EMG
`response with a V greater than Vs. This first stimulation
`current to recruit, together with the last stimulation current to
`have not recruited, forms the initial bracket.
`After bracketing the threshold current I, the bisection
`method is used to reduce the bracket to a selected width or
`resolution. The stimulation current at the midpoint of the
`bracket is used. If the stimulation current recruits, the bracket
`shrinks to the lower half of the previous range. If the stimu
`lation current does not recruit, the bracketshrinks to the upper
`half of the previous range. This process continues until I,
`is bracketed by stimulation currents separated by the selected
`width or resolution. It
`is preferably defined as the mid
`point of this final bracket. The bracketing and bisection steps
`may be repeated and I, found for each channel unless the
`threshold exceeds a predetermined maximum current.
`To reduce the number of stimulations required to complete
`the bracketing and bisection steps when I, is determined
`repeatedly and/or over multiple channels, the algorithm omits
`stimulations for which the result is predictable from data
`acquired during previous stimulations. When a stimulation is
`omitted, the algorithm proceeds as if the stimulation had
`taken place. However, instead of reporting an actual recruit
`ment result, the reported result is inferred from the previous
`data. This permits the algorithm to proceed to the next step
`immediately, without the delay associated with a stimulation.
`For every stimulation signal delivered, the EMG response, or
`lack thereof, is detected and recorded on each channel (no
`matter which channel is actually being processed for I).
`Later the data can be referred back to, allowing the algorithm
`to omit a stimulation and infer whether or not the channel
`would recruit at the given stimulation current.
`There are two scenarios in which the algorithm may omita
`stimulation and report previously obtained recruitment
`results. A stimulation may be omitted if the selected stimula
`tion current would be a repeat of a previous stimulation. If the
`specific stimulation current is not a repeat, the stimulation
`may be omitted if the results are already clear from the pre
`vious data.
`
`Petitioner - Avation Medical, Inc.
`Ex. 1029, p. 16
`
`

`

`feefatia
`
`3
`To determine whether to deliver an actual stimulation or
`omit the stimulation and report previous results, the algorithm
`first checks whether the selected stimulation current has been
`previously used. If the stimulation current has been used, the
`stimulation is omitted and the results of the previous stimu
`lation are reported for the present channel. If the stimulation
`current has not been used, the algorithm determines I,
`and I,
`for the present channel. I
`is the lowest
`stimulation current that has recruited on the present channel.
`It is the highest stimulation current that has failed to
`recruit on the present channel. If I
`is not greater than
`I, the algorithm will stimulate at the selected current
`and report the results for the present channel. If I
`is
`greater than I,
`the algorithm identifies whether the
`selected Stimulation current is higher than I, lower than
`I,
`or between I, and I. If the selected Stimu
`lation current is higher than I, the algorithm omits the
`stimulation and reports that the present channel recruits at the
`specified current. Conversely, when the selected stimulation
`current is lower than I,
`the algorithm infers that the
`present channel will not recruit at the selected current and
`reports that result. If the selected stimulation current falls
`between I, and I, the result of the stimulation
`cannot be inferred. The algorithm stimulates at the selected
`current and reports the results for the present channel. This
`method may be repeated until I, has been determined for
`every active channel.
`The order in which channels are processed is immaterial.
`The channel processing order may be biased to yield the
`highest or lowest threshold first or an arbitrary processing
`order may be used. It is also not necessary to complete the
`algorithm for one channel before beginning to process the
`next channel. Channels are still processed one at a time,
`however, the algorithm may cycle between one or more chan
`nels, processing as few as one stimulation current for that
`channel before moving on to the next channel. In this manner
`the algorithm may advance all channels essentially together
`and bias the order to find the lower threshold channels first or
`the higher threshold channels first.
`To further reduce the number of stimulations required to
`repeatedly find I, over the course of a procedure, the
`algorithm includes a confirmation step. If I
`has been
`previously determined for a specific channel, the algorithm
`may simply confirm that I
`has not changed rather than
`beginning anew with the bracketing and bisection methods.
`The algorithm first determines whether it is conducting the
`initial threshold determination for the channel or whether
`there is a previous I, determination. If it is not the initial
`determination, the algorithm confirms the previous determi
`nation. If the previous threshold is confirmed, the algorithm
`reports that value as the present Is. If it is the initial I,
`determination or if the previous threshold cannot be con
`firmed, the algorithm enters the bracketing and bisection
`states to determine I, and then reports the value.
`55
`The confirmation step attempts to ascertain whether I,
`has moved from its last known value. To do this, the algorithm
`applies two stimulation currents, one at or just above the
`threshold value and one just below the threshold value. If the
`stimulation at or above I, recruits and the stimulation just
`below I
`does not recruit, then I, is confirmed and the
`algorithm may report the initial value again as I,
`and
`proceed to process another channel. If the stimulation just
`below It, recruits, it may be concluded that Is, has
`decreased and likewise, if the stimulation at or just above
`Its, fails to recruit, it may be assumed that It, has
`increased and therefore I
`cannot be confirmed.
`
`40
`
`45
`
`50
`
`60
`
`65
`
`US 8,206,312 B2
`
`10
`
`15
`
`25
`
`30
`
`35
`
`4
`cannot be confirmed, the algorithm enters the
`If I
`bracketing State. Rather than beginning the bracketing State
`from the minimum stimulation current, however, the brack
`eting state may begin from the previous I. The bracketing
`may advance up or down depending on whether I, has
`increased or decreased. When the algorithm enters the brack
`eting state, the increment used in the confirmation step is
`exponentially doubled until the channel recruits, at which
`time it enters the bisection state. The confirmation step may
`be performed for each channel, in turn, in any order. Again
`stimulations may