The Role of Intraoperative Neuromonitoring (IONM)

Comprehensive Care of Spine Pathologies, October 13, 2012Comprehensive Care of Spine Pathologies, October 13, 2012
The Role of Intraoperative NeuromonitoringThe Role of Intraoperative Neuromonitoring
David Barnkow, AuD, DABNM, CNIMDavid Barnkow, AuD, DABNM, CNIM
Who? What? When? Where? Why? How?Who? What? When? Where? Why? How?
Image Source: http://themostimportantnews.com/archives/new-poll-45-percent-of-american-doctors-would-consider-quitting-or-retiring-if-Image Source: http://themostimportantnews.com/archives/new-poll-45-percent-of-american-doctors-would-consider-quitting-or-retiring-if-
obamacare-is-adoptedobamacare-is-adopted

Image Retrieved 9/11/2012 from: http://computingforsustainability.files.wordpress.com/2011/04/trolley-Image Retrieved 9/11/2012 from: http://computingforsustainability.files.wordpress.com/2011/04/trolley-
problem.jpg, modified without permission.problem.jpg, modified without permission.
What?What?
What’s the problem?What’s the problem?

What?What?
Image Retrieved 9/11/2012 from: http://computingforsustainability.files.wordpress.com/2011/04/trolley-problem.jpg,Image Retrieved 9/11/2012 from: http://computingforsustainability.files.wordpress.com/2011/04/trolley-problem.jpg,
modified without permission.modified without permission.

What?What?
Iatrogenic injuryIatrogenic injury
Iatrogenic i·at·ro·gen·ic (ī-āt'r -jěn'ĭk) adj.əIatrogenic i·at·ro·gen·ic (ī-āt'r -jěn'ĭk) adj.ə
Induced in a patient by a physician'sInduced in a patient by a physician's
activity, manner, or therapy.activity, manner, or therapy.
The American Heritage® Stedman's Medical DictionaryThe American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

What?What?
Iatrogenic neurological injury in spine surgeryIatrogenic neurological injury in spine surgery
can be caused by:can be caused by:
SurgicalSurgical
Distraction, compression or blunt traumaDistraction, compression or blunt trauma
Ischemia of neural structuresIschemia of neural structures
Thrombotic eventsThrombotic events
Anesthetic or Systemic ProblemsAnesthetic or Systemic Problems
Ischemia,Ischemia,
hypoxiahypoxia
hypothermiahypothermia
cervical extension during intubationcervical extension during intubation
PositioningPositioning
Direct compressionDirect compression
Compromised blood supplyCompromised blood supply
Neck and shoulder positioningNeck and shoulder positioning

What?What?
What is the incidence of iatrogenic injury in elective spineWhat is the incidence of iatrogenic injury in elective spine
surgery?surgery?
Iatrogenic neurological injuries in elective spinal surgeryIatrogenic neurological injuries in elective spinal surgery
without neurophysiological monitoring:without neurophysiological monitoring:
Anterior cervical discectomy – 0.46%Anterior cervical discectomy – 0.46%
Scoliosis correction - 0.23-3.2%Scoliosis correction - 0.23-3.2%
Intramedullary tumor resection - >23.8%Intramedullary tumor resection - >23.8%
Vauzelle C, Stagnara P, Jouvinroux P. Functional monitoring of spinal cord activity during spinal surgery.Vauzelle C, Stagnara P, Jouvinroux P. Functional monitoring of spinal cord activity during spinal surgery.
Clin Orthop Relat Res 1973;93:173-8Clin Orthop Relat Res 1973;93:173-8

Why?Why?
Why avoid iatrogenic injury?Why avoid iatrogenic injury?
To improve or maintain quality of life.To improve or maintain quality of life.
(WHO - HRQOL)(WHO - HRQOL)
People with spinal cord injury (SCI):People with spinal cord injury (SCI):
report lower sense of well-beingreport lower sense of well-being
score lower on physical, mental, and social healthscore lower on physical, mental, and social health
domainsdomains
Dijkers, M: Quality of life of individuals with spinal cord injury: A review of conceptualization,Dijkers, M: Quality of life of individuals with spinal cord injury: A review of conceptualization,
measurement, and research findings. J. Rehab Res & Dev, Supplement Number 1, Volume 42 Numbermeasurement, and research findings. J. Rehab Res & Dev, Supplement Number 1, Volume 42 Number
3, May/June 2005, Pages 87-110. Retrieved 9/11/12 from3, May/June 2005, Pages 87-110. Retrieved 9/11/12 from
http://www.rehab.research.va.gov/jour/05/42/3suppl1/dijkers.htmlhttp://www.rehab.research.va.gov/jour/05/42/3suppl1/dijkers.html

Why?Why?
To improve or maintain quality of life. (WHO – HRQOL)To improve or maintain quality of life. (WHO – HRQOL)
““Life expectancies for persons with SCI continue toLife expectancies for persons with SCI continue to
increase, but are still somewhat below life expectanciesincrease, but are still somewhat below life expectancies
for those with no SCI.”for those with no SCI.”
National Spinal Cord Injury Statistical Center, Birmingham, Alabama, Spinal Cord Injury Facts and Figures at aNational Spinal Cord Injury Statistical Center, Birmingham, Alabama, Spinal Cord Injury Facts and Figures at a
Glance, February 2012, retrieved 9/11/12 atGlance, February 2012, retrieved 9/11/12 at
https://www.nscisc.uab.edu/PublicDocuments/fact_figures_docs/Facts%202012%20Feb%20Final.pdfhttps://www.nscisc.uab.edu/PublicDocuments/fact_figures_docs/Facts%202012%20Feb%20Final.pdf

Why?Why?
Reduce the costs associated with iatrogenic injury.Reduce the costs associated with iatrogenic injury.
The average yearly health care and living expenses directlyThe average yearly health care and living expenses directly
attributable to SCI was $69,204 in February 2012 dollars.attributable to SCI was $69,204 in February 2012 dollars.
These figures do not include any indirect costs such as lossesThese figures do not include any indirect costs such as losses
in wages, fringe benefits and productivity.in wages, fringe benefits and productivity.
National Spinal Cord Injury Statistical Center, Birmingham, Alabama, Spinal Cord Injury Facts and Figures at a Glance,National Spinal Cord Injury Statistical Center, Birmingham, Alabama, Spinal Cord Injury Facts and Figures at a Glance,
February 2012, retrieved Sept. 11, 20112 at https://www.nscisc.uab.edu/PublicDocuments/fact_figures_docs/FactsFebruary 2012, retrieved Sept. 11, 20112 at https://www.nscisc.uab.edu/PublicDocuments/fact_figures_docs/Facts
%202012%20Feb%20Final.pdf%202012%20Feb%20Final.pdf

How?How?
How can we avoid iatrogenic injury?How can we avoid iatrogenic injury?
Timely detection of changes inTimely detection of changes in
neurologic status allowsneurologic status allows
therapeutic actiontherapeutic action to ameliorateto ameliorate
or avoid neurologic deficitsor avoid neurologic deficits.

How?How?
How can we detect changes inHow can we detect changes in
neurologic status?neurologic status?
Functional vs. Structural AssessmentFunctional vs. Structural Assessment
Structural AssessmentStructural Assessment
RadiographyRadiography
SonographySonography
VisualizationVisualization

How?How?
How can we detect changes inHow can we detect changes in
neurologic status?neurologic status?
Function AssessmentFunction Assessment
Using provocative and non-provocativeUsing provocative and non-provocative
techniques.techniques.
Intraoperative Neurophysiologic MonitoringIntraoperative Neurophysiologic Monitoring
(IONM)(IONM)

How?How?
How is IONM performed?How is IONM performed?
Electrophysiologic AssessmentsElectrophysiologic Assessments
Non-ProvocativeNon-Provocative
Spontaneous electromyography (sEMG)Spontaneous electromyography (sEMG)
Electroencephalography (EEG)Electroencephalography (EEG)
ProvocativeProvocative
Triggered electromyography (tEMG)Triggered electromyography (tEMG)
Electroencephalography (EEG)Electroencephalography (EEG)
Evoked Potentials (EP)Evoked Potentials (EP)
Somatosensory (SSEP)Somatosensory (SSEP)
Motor (MEP)Motor (MEP)
Nerve Conduction Study (NCS)Nerve Conduction Study (NCS)

How?How?
How effective is IONM?How effective is IONM?
Efficacy of IONM in Cervical Spine SurgeryEfficacy of IONM in Cervical Spine Surgery
Somatosensory evoked potentialsSomatosensory evoked potentials
sensitivity -sensitivity - 52% (+ correctly ID'd)52% (+ correctly ID'd)
specificity -specificity - 100% (- correctly ID'd)100% (- correctly ID'd)
PPV -PPV - 100% (true +/+calls)100% (true +/+calls)
NPV -NPV - 97% (true -/- calls)97% (true -/- calls)
Motor evoked potentialsMotor evoked potentials
sensitivity -sensitivity - 100%100%
specificity -specificity - 96%96%
PPV -PPV - 96%96%
NPV -NPV - 100%100%
ElectromyographyElectromyography
PPV -PPV - 3%3%
NPV -NPV - 97%97%
Kelleher MO, Tan G, Sarjeant R, Fehlings MG: Predictive value of intraoperative neurophysiological monitoring during cervical spine surgery: a prospective analysisKelleher MO, Tan G, Sarjeant R, Fehlings MG: Predictive value of intraoperative neurophysiological monitoring during cervical spine surgery: a prospective analysis
of 1055 consecutive patients. J Neurosurg Spine. 2008 Mar;8(3):215-21.of 1055 consecutive patients. J Neurosurg Spine. 2008 Mar;8(3):215-21.

How?How?
Efficacy of IONM in ThorocolumbarEfficacy of IONM in Thorocolumbar
Spine Surgery (nerve root emphasis)Spine Surgery (nerve root emphasis)
SSEPsSSEPs
sEMGsEMG
specificity -specificity - 23.7%23.7%

How?How?
Multimodal IONM reduces the relative risk of post-Multimodal IONM reduces the relative risk of post-
operative neurological complications in spine surgery by anoperative neurological complications in spine surgery by an
estimated 49.4% at a mean cost of $63,387 per neurologicalestimated 49.4% at a mean cost of $63,387 per neurological
deficit averted.deficit averted.
Ney JP, Van der Goes DN, Watanabe JH: Cost-effectiveness of intraoperative neurophysiological monitoring for spinalNey JP, Van der Goes DN, Watanabe JH: Cost-effectiveness of intraoperative neurophysiological monitoring for spinal
surgeries: Beginning steps, Clinical Neurophysiology, Volume 123, Issue 9, Pages 1705-1707, September 2012surgeries: Beginning steps, Clinical Neurophysiology, Volume 123, Issue 9, Pages 1705-1707, September 2012

When?When?
When is IONM appropriate?When is IONM appropriate?
Identify iatrogenic nervous system compromise in aIdentify iatrogenic nervous system compromise in a
timely fashion.timely fashion.
Ongoing monitoringOngoing monitoring
Identify neural structures through specific testingIdentify neural structures through specific testing
procedures.procedures.
Time-Specific assessmentTime-Specific assessment
Identify when iatrogenic injury occurred inIdentify when iatrogenic injury occurred in
experimental procedures.experimental procedures.
Ongoing monitoringOngoing monitoring

Where?Where?
Where can IONM be performed?Where can IONM be performed?
On the hospital floorsOn the hospital floors
In Pre-Op HoldingIn Pre-Op Holding
In the Operating RoomIn the Operating Room

Who?Who?
Who provides IONM?Who provides IONM?
Technologists – Technical ComponentTechnologists – Technical Component
•Associate and Bachelor Degrees.Associate and Bachelor Degrees.
•Trained in the technical aspects of data collection.Trained in the technical aspects of data collection.
•Lack training and knowledge to provideLack training and knowledge to provide
interpretation, diagnosis and treatmentinterpretation, diagnosis and treatment
Credentials:Credentials:
•ABRET - American Board of Registration ofABRET - American Board of Registration of
Electroencephalographic and Evoked PotentialElectroencephalographic and Evoked Potential
TechnologistsTechnologists
•CNIM - Certificate in NeurophysiologicCNIM - Certificate in Neurophysiologic
Intraoperative MonitoringIntraoperative Monitoring

Who?Who?
Non-Physician Surgical Neurophysiologist – ProfessionalNon-Physician Surgical Neurophysiologist – Professional
ComponentComponent
•Non-MD providers with Doctorate Degrees.Non-MD providers with Doctorate Degrees.
•Technical Support for CNIMs.Technical Support for CNIMs.
•Technical ComponentTechnical Component
•Site-specific credentials may allow:Site-specific credentials may allow:
Supervision dutiesSupervision duties
Interpretation with treatment suggestions toInterpretation with treatment suggestions to
surgical team M.D.s.surgical team M.D.s.
Credentials:Credentials:
•ABNM – American Board of NeurophysiologicABNM – American Board of Neurophysiologic
MonitoringMonitoring
•Diplomat – D.ABNMDiplomat – D.ABNM

Who?Who?
Clinical Neurophysiologist – Medical ComponentClinical Neurophysiologist – Medical Component
Medical Doctors – M.D. and D.O. With specificMedical Doctors – M.D. and D.O. With specific
certification.certification.
InterpretationInterpretation
DiagnosisDiagnosis
TreatmentTreatment
Credentials: Certification from;Credentials: Certification from;
ABPN -ABPN - American Board of Psychiatry and NeurologyAmerican Board of Psychiatry and Neurology
ABCN -ABCN - American Board of Clinical NeurophysiologyAmerican Board of Clinical Neurophysiology
ABEM -ABEM - American Board of Emergency MedicineAmerican Board of Emergency Medicine
ABNM –ABNM – American Board of NeurophysiologicAmerican Board of Neurophysiologic
MonitoringMonitoring

Retrieved on 9/12/12 from; http://en.wikipedia.org/wiki/File:Gray759.png
Anatomy ReviewAnatomy Review
Sensory InputSensory Input
Posterior Dorsal Column-Posterior Dorsal Column-
Lemniscal TractLemniscal Tract
Conveys touch, vibrationConveys touch, vibration
and proprioceptionand proprioception
information to the brain.information to the brain.

Corticospinal TractCorticospinal Tract
Voluntary skilledVoluntary skilled
activityactivity
Pre-central gyrus ofPre-central gyrus of
cortex to spinal cordcortex to spinal cord
without interruptionwithout interruption
Retrieved on 9/12/12 from:http://en.wikipedia.org/wiki/File:Gray764.pngRetrieved on 9/12/12 from:http://en.wikipedia.org/wiki/File:Gray764.png

Retrieved on 9/12/2012 from; http://en.wikipedia.org/wiki/File:Medulla_spinalis_-_tracts_-Retrieved on 9/12/2012 from; http://en.wikipedia.org/wiki/File:Medulla_spinalis_-_tracts_-
_English.svg_English.svg
Spinal Cord AnatomySpinal Cord Anatomy
Blood supply of dorsal 1/3Blood supply of dorsal 1/3
of spinal cord via the twoof spinal cord via the two
posterior spinal arteries.posterior spinal arteries.
Blood supply of theBlood supply of the
anterior 2/3 of spinal cordanterior 2/3 of spinal cord
via the single anteriorvia the single anterior
spinal artery.spinal artery.

Anterior Spinal ArteryAnterior Spinal Artery
Spinal cord bloodSpinal cord blood
supply and watershedsupply and watershed
regionsregions
Nuwer MR, Handbook of Clinical Neurophysiology Volume 8; IntraoperativeNuwer MR, Handbook of Clinical Neurophysiology Volume 8; Intraoperative
Monitoring of Neural Function.(2008). Elsevier, Daube and Mauguiere Eds. Pg 58Monitoring of Neural Function.(2008). Elsevier, Daube and Mauguiere Eds. Pg 58

Nerve RootsNerve Roots
Retrieved on 9/12/2012 from http://en.wikipedia.org/wiki/File:Spinal_nerve.svgRetrieved on 9/12/2012 from http://en.wikipedia.org/wiki/File:Spinal_nerve.svg

Retrieved on 9/12/12 fromRetrieved on 9/12/12 from
http://upload.wikimedia.org/wikipedia/commons/a/ad/Foraminaintervertebrhttp://upload.wikimedia.org/wikipedia/commons/a/ad/Foraminaintervertebr
alia.pngalia.png
IntervertebralIntervertebral
ForamenForamen

Electrophysiological Techniques in IONMElectrophysiological Techniques in IONM
Spontaneous EMG (sEMG)Spontaneous EMG (sEMG)
Triggered EMG (tEMG)Triggered EMG (tEMG)
Nerve Conduction Study (NCS)Nerve Conduction Study (NCS) low relevance to spine surgerylow relevance to spine surgery
Electroencephalography (EEG)Electroencephalography (EEG) low relevance to spine surgerylow relevance to spine surgery

ElectrophysiologicalElectrophysiological
Techniques in IONMTechniques in IONM
Stimulation:Stimulation:
electrical, peripheral mixed nerve.electrical, peripheral mixed nerve.
Recording:Recording:
neurogenic. peripheral,neurogenic. peripheral,
subcortical, cortical.subcortical, cortical.
Use:Use:
monitor dorsal spinal cordmonitor dorsal spinal cord
(afferent) and afferent peripheral(afferent) and afferent peripheral
nervesnerves

Retrieved on 9/12/12 from; http://en.wikipedia.org/wiki/File:Gray759.pngRetrieved on 9/12/12 from; http://en.wikipedia.org/wiki/File:Gray759.png
electrical, peripheralelectrical, peripheral
mixed nervemixed nerve
neurogenic.neurogenic.
peripheral,peripheral,
subcortical, corticalsubcortical, cortical

Electrical orElectrical or
MagneticMagnetic
Neurogenic - SpinalNeurogenic - Spinal
CordCord
Myogenic - MusclesMyogenic - Muscles
of Interestof Interest
Use:Use:
Monitor anteriorMonitor anterior
spinal cord andspinal cord and
efferent peripheralefferent peripheral
nervesnerves
Retrieved on 9/12/12 from:http://en.wikipedia.org/wiki/File:Gray764.pngRetrieved on 9/12/12 from:http://en.wikipedia.org/wiki/File:Gray764.png

Recording and interpretation of muscle activity inRecording and interpretation of muscle activity in
real time.real time.
Spontaneous EMG (sEMG)Spontaneous EMG (sEMG)
NoneNone
Continuous recording of musclesContinuous recording of muscles
innervated by nerve roots at riskinnervated by nerve roots at risk
Surface or needle electrodesSurface or needle electrodes
Use:Use:
Detect mechanical nerve root irritationDetect mechanical nerve root irritation

Recording and interpretation of muscle activity in realRecording and interpretation of muscle activity in real
timetime
Triggered EMG (tEMG)Triggered EMG (tEMG)
electricalelectrical
Brief, time-locked muscle activityBrief, time-locked muscle activity
Use:Use:
Differentiate tissueDifferentiate tissue
Compute nerve conduction velocityCompute nerve conduction velocity
(NCV)(NCV)
Assess pedicle screw integrityAssess pedicle screw integrity

Let us look at IONM in:Let us look at IONM in:
Spinal Deformity SurgerySpinal Deformity Surgery
Spinal Decompression SurgerySpinal Decompression Surgery
Anterior Cervical Discectomy and FusionAnterior Cervical Discectomy and Fusion

IONM inIONM in
Times of Risk:Times of Risk:
Induction: Low unless spinal instabilityInduction: Low unless spinal instability
Positioning: Low unless symptoms easily provokedPositioning: Low unless symptoms easily provoked
Surgical: Significant during deformity correctionSurgical: Significant during deformity correction
pedicle screw implantationpedicle screw implantation

IONM inIONM in
Structures at Risk:Structures at Risk:
Primary:Primary:
Spinal cordSpinal cord
Mechanism: Cord distraction and compression,Mechanism: Cord distraction and compression,
ischemiaischemia
Nerve RootsNerve Roots
Mechanism: Trauma, compression, hardwareMechanism: Trauma, compression, hardware
Secondary:Secondary:
Peripheral nerves and brachial plexusPeripheral nerves and brachial plexus
Mechanism: Stretch and compressionMechanism: Stretch and compression

IONM inIONM in
Modalities Monitored:Modalities Monitored:
SSEP – dorsal spinal cord and peripheral nervesSSEP – dorsal spinal cord and peripheral nerves
MEP – ventral spinal cord and peripheral nervesMEP – ventral spinal cord and peripheral nerves
sEMG, tEMG – nerve rootssEMG, tEMG – nerve roots

IONM inIONM in
63 year old female with 20 year history of C5-6 tetraplegia with63 year old female with 20 year history of C5-6 tetraplegia with
partial zone preservation to left C7 myotome, and post traumaticpartial zone preservation to left C7 myotome, and post traumatic
tethered spinal cord due to MVA.tethered spinal cord due to MVA.
Planned procedure: cervical laminectomy, spinal cordPlanned procedure: cervical laminectomy, spinal cord
untethering, expansion duraplasty.untethering, expansion duraplasty.
Spoiler Alert: These data suggested the possibility of transientSpoiler Alert: These data suggested the possibility of transient
changes in the left side sensory and motor neurological statuschanges in the left side sensory and motor neurological status
during this procedure.during this procedure.

IONM in Spinal Deformity SurgeryIONM in Spinal Deformity Surgery
63 year old female with 20 year history of C5-6 tetraplegia63 year old female with 20 year history of C5-6 tetraplegia
Prepositioning Data – Ulnar and Tibial SSEPPrepositioning Data – Ulnar and Tibial SSEP

Prepositioning Data - MEPPrepositioning Data - MEP

9:20 - Post-positioning Data – Ulnar SSEP9:20 - Post-positioning Data – Ulnar SSEP
9:29 – Reposition left arm9:29 – Reposition left arm
9:39 – No Ulnar SSEP Cortical Response. Neck repositioned9:39 – No Ulnar SSEP Cortical Response. Neck repositioned
9:49 – Left Ulnar stimulation moved to elbow.9:49 – Left Ulnar stimulation moved to elbow.
9:59 – Patient returned to bed.9:59 – Patient returned to bed.
10:30 – Prone on OR table.10:30 – Prone on OR table.
10:33 – Median Stimulation in Ulnar Test10:33 – Median Stimulation in Ulnar Test
11:02 – Surgery aborted.11:02 – Surgery aborted.

Post-positioning Data – MEPPost-positioning Data – MEP
9:20 - Post-positioning Data – Ulnar SSEP9:20 - Post-positioning Data – Ulnar SSEP
9:29 – Reposition left arm9:29 – Reposition left arm
9:39 – No Ulnar SSEP Cortical Response. Neck repositioned.9:39 – No Ulnar SSEP Cortical Response. Neck repositioned.
9:49 – Left Ulnar stimulation moved to elbow.9:49 – Left Ulnar stimulation moved to elbow.
10:30 – Prone on OR table.10:30 – Prone on OR table.
11:02 – Surgery aborted.11:02 – Surgery aborted.

63 year old female with 20 year history of C5-663 year old female with 20 year history of C5-6
tetraplegiatetraplegia
Surgery was aborted.Surgery was aborted.
Clinical exam in post-op recovery demonstratedClinical exam in post-op recovery demonstrated
no new neurological deficits.no new neurological deficits.

IONM inIONM in
Induction: LowInduction: Low
Positioning: Moderate for mechanical irritation of nerve rootPositioning: Moderate for mechanical irritation of nerve root
Surgical: Significant during decompression.Surgical: Significant during decompression.

IONM inIONM in
Primary:Primary:
Nerve rootsNerve roots
Mechanism: Trauma, stretchingMechanism: Trauma, stretching
Spinal cordSpinal cord
Mechanism: IschemiaMechanism: Ischemia
Peripheral nerves and brachial plexusPeripheral nerves and brachial plexus
Mechanism: Compression, stretchingMechanism: Compression, stretching

IONM inIONM in
sEMG – nerve rootssEMG – nerve roots
SSEP – spinal cord and peripheral nervesSSEP – spinal cord and peripheral nerves
tEMG, MEP (optional)tEMG, MEP (optional)

IONM inIONM in
68 year old female with L4-5 DDD, spondylolisthesis, spinal stenosis, radiculopathy68 year old female with L4-5 DDD, spondylolisthesis, spinal stenosis, radiculopathy
Procedure: PSF, PLIF L4-5Procedure: PSF, PLIF L4-5
Laminectomy in progress.Laminectomy in progress.

IONM inIONM in
Rasp on End-plate prior to cage implantation.Rasp on End-plate prior to cage implantation.

IONM inIONM in
68 year old female with L4-5 DDD, spondylolisthesis, spinal68 year old female with L4-5 DDD, spondylolisthesis, spinal
stenosis, radiculopathystenosis, radiculopathy
Triggered EMG – Pedicle Screw Stimulation ThresholdsTriggered EMG – Pedicle Screw Stimulation Thresholds
Acceptable LimitsAcceptable Limits >> 8 mA.8 mA.
SiteSite LeftLeft RightRight
L4 screwL4 screw 8 mA (2nd, 15 mA)8 mA (2nd, 15 mA) 30 mA30 mA
L5 screwL5 screw 36 mA36 mA 33 mA33 mA
L5 nerveL5 nerve 0.2 mA0.2 mA

IONM inIONM in
Examine left L4 pedicle due to low screw threshold.Examine left L4 pedicle due to low screw threshold.

IONM inIONM in
Induction: Possibly SignificantInduction: Possibly Significant
Positioning: Possibly SignificantPositioning: Possibly Significant
Surgical: SignificantSurgical: Significant

IONM inIONM in
Primary:Primary:
Spinal Cord, Cervical Nerve RootsSpinal Cord, Cervical Nerve Roots
Recurrent Laryngeal Nerve, Brachial PlexusRecurrent Laryngeal Nerve, Brachial Plexus

IONM inIONM in
MEPMEP
SSEPSSEP
Recurrent Laryngeal (CN X) Nerve sEMGRecurrent Laryngeal (CN X) Nerve sEMG
sEMGsEMG

IONM inIONM in
59 year old male59 year old male
Dx: DDD C5-6Dx: DDD C5-6
Procedure: Artificial Disc C5-6Procedure: Artificial Disc C5-6

IONM inIONM in
Artificial Disc C5-6Artificial Disc C5-6

The EndThe End

The Role of Intraoperative Neuromonitoring (IONM)

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