Utilization of facial nerve monitoring: A survey of ...
Transcript of Utilization of facial nerve monitoring: A survey of ...
Audiology or not?Intraoperative neuromonitoring
Audiology or not?Audiology or not?IntraoperativeIntraoperative neuromonitoringneuromonitoring
William Hal Martin, Ph.D.Oregon Hearing Research CenterOregon Health Science University
American Academy of AudiologySan Diego, 2010
Role of the Audiologist in the Role of the Audiologist in the Operating RoomOperating Room
Other than physicians, audiologistsare the only other professionals who are, by definition of scope-of-practice, qualified to perform and interpret intraoperative neurophysiological monitoring.
Intraoperative Intraoperative Neurophysiological MonitoringNeurophysiological Monitoring
Intraoperative – during a surgical
procedure
Neurophysiological – related to brain or
nerve function
Monitoring – continual testing and
interpreting results
What do we monitor?What do we monitor?
• Pathways
–– Ascending (sensory) systemsAscending (sensory) systems
–– Descending (motor) systemsDescending (motor) systems
How do we monitor?How do we monitor?
• Pathways
–– Stimulate one endStimulate one end
–– Record at the other endRecord at the other end
–– Identify changes along the Identify changes along the pathway due to the surgerypathway due to the surgery
Why do we monitor?Why do we monitor?
• To reduce surgically related mobidity and mortality
• To protect the brain, nerves and spinal cord
When do we monitor?When do we monitor?• Whenever the surgical team believes
that the brain or nerve pathways are at risk due to: –– The nature or extent of the diseaseThe nature or extent of the disease–– The complexity of the surgical The complexity of the surgical
approachapproach
Who does monitoring?Who does monitoring?• Technical – Trained to perform
modified electrodiagnostic tests during surgery
• Professional – Trained to interpret changes in responses
• Both – Trained to perform AND interpret tests in real time
ControversiesControversies
• “Remote” supervision–– tech in the room and interpretation tech in the room and interpretation
done elsewheredone elsewhere
• Surgeon interpretation–– Automated systems that require the Automated systems that require the
surgeon to interpret results while surgeon to interpret results while operatingoperating
MontioringMontioring ProceduresProcedures• Auditory brainstem responses• Electrocochleography• Cranial nerve electromyography• Somatosensory evoked potentials• Electromyography (EMG)• Electrocorticography• Electroencephalography (EEG)• Motor evoked potentials w/EMG
ProblemProblem
Hearing and brainstem function can be damaged during cerebello-pontine angle surgery
Site of DamageSite of Damage
•• CochleaCochlea
•• Cochlear NerveCochlear Nerve
•• Brainstem Auditory PathwayBrainstem Auditory Pathway
ProceduresProcedures
•• CPA Tumor resectionCPA Tumor resection•• Vestibular nerve sectionVestibular nerve section•• MicrovascularMicrovascular decompressiondecompression•• Aneurysm repairAneurysm repair•• AVM repairAVM repair
Techniques: Techniques: Electrocochleography (EcochG)Electrocochleography (EcochG)
•• Information about the cochlea (SP) and Information about the cochlea (SP) and distal cochlear nerve (Wave I)distal cochlear nerve (Wave I)
•• Recorded from ear canal, tympanic Recorded from ear canal, tympanic membrane or promontorymembrane or promontory
•• Large signalLarge signal
N1
-
Electrocochleogram
2 ms
TM-Cz
1 µV
Techniques:Techniques:Auditory nerve compound action Auditory nerve compound action
potentialspotentials
•• Information about the proximal cochlear Information about the proximal cochlear nerve at the root entry zonenerve at the root entry zone
•• Recorded from wick, silver ball or hook Recorded from wick, silver ball or hook electrode placed by surgeonelectrode placed by surgeon
•• Giant signal Giant signal
Inferior vestibular nerveSuperior vestibular nerve
Auditory nerve
VVIII
IXXXI
Lang, 1985
VIII
IXX
XI
N1
P1
–
2 ms
Compound Action Potential
5 µV
Techniques: Techniques: Auditory Brainstem ResponsesAuditory Brainstem Responses
•• Information about the auditory Information about the auditory pathway through the midbrainpathway through the midbrain
•• Recorded from scalpRecorded from scalp
•• Small signalSmall signal
Morest, 1975
Cz-M ipsilateral
I
II
IIIV
IV
IIIII
VIV
2 ms
Auditory Brainstem Response
+
Cz-M contralateral
200 nV
StrategyStrategy
•• Smaller tumors Smaller tumors -- save hearing YESsave hearing YESEcochG, ANEcochG, AN--CAP, ABR tumor sideCAP, ABR tumor side
•• Medium tumors Medium tumors -- save hearing ??save hearing ??EcochG, ABR both sidesEcochG, ABR both sides
•• Larger tumors Larger tumors -- save hearing NOsave hearing NOABR nonABR non--tumor sidetumor side
Techniques: Techniques: Auditory Brainstem ResponsesAuditory Brainstem Responses
•• Information about the auditory Information about the auditory pathway through the midbrainpathway through the midbrain
•• Recorded from scalpRecorded from scalp
•• Small signalSmall signal
Interpretation:Interpretation:Changes in ABRChanges in ABR
• ↑ III-V IPI = rostral, systemic changes
• ↑ I-III IPI = changes in auditory function
• III Amplitude ↓ = earliest ABR predictor of postop deafness
Interpretation:Interpretation:Changes in ANChanges in AN--CAPCAP
• Latency ↑ = stretch nerve
• Amplitude ↓ = compressed nerve
• Absent N1 = total conduction block
1.5 µV–
0 10 20 ms
N1
P1
Møller, 1995
Interpretation:Interpretation:Criteria for concernCriteria for concern
Any change beyond the test-retest variability within a case should be considered a cause for concern
Case study:Case study:Total conduction blockTotal conduction block
• 62 y.o. female
• 1.5 cm vestibular schwannoma in left IAC
• Vertigo, left side tinnitus, mild high-frequency hearing loss
• Normal word recognition normal ABR
• Hearing preservation high priority
Pre-operative
Nerve exposed
Drilling canal
Resecting tumor
EcochG 500 nV 200 nV1.2 µVAN-CAP ABR +––
Resecting tumor
Resecting tumor
Resecting tumor
Resecting tumor
20 ms0
V
N1
P1
N1
Prell et al. 2008
Examples of mechanically evoked facial nerve activity
Motor Cranial Nerve MonitoringMotorMotor Cranial Nerve MonitoringCranial Nerve Monitoring
• Recordings made from muscles
innervated by cranial nerves at-risk
• Direct stimulation of cranial nerves
for:
–– identificationidentification
–– testing function testing function
ElectromyographyElectromyography
Cranial Nerve VII: FacialCranial Nerve VII: Facial• Intracranial
–– CPA CPA tumor resections
–– MVDMVD–– Vestibular nerve Vestibular nerve
sectionsection
• Intratemporal– Facial Nerve
decompression– Mastoidectomy– Tympanoplasty– Cochlear implant– Translab approach – Labrynthectomy
The Human SpineThe Human Spine
• Magnificently designed structure
–– Form and function Form and function -- vertebraevertebrae
•• StructureStructure
•• StrengthStrength
•• FlexibilityFlexibility
•• ProtectionProtection
Normal Spinal Column
View from left View from back
Spinal DeformitiesSpinal Deformities
• Examples
––ScoliosisScoliosis
––KyphosisKyphosis
––SpondylolisthesisSpondylolisthesis
Scoliosis Normal
Spinal Cord MonitoringSpinal Cord MonitoringSpinal Cord Monitoring
• Spinal tumors
• Spinal trauma
• Spinal deformities
Intraoperative Monitoring:Somatosensory Evoked
Potentials
Intraoperative Monitoring:Intraoperative Monitoring:Somatosensory Evoked Somatosensory Evoked
PotentialsPotentials
Monitoring Recommendations
Monitoring Recommendations
• Median n. stimulation
––Spinal cord surgery above C8Spinal cord surgery above C8
• Posterior Tibial n. stimulation
––Spinal cord surgery below C8Spinal cord surgery below C8
• Monitors SENSORY pathways
Mechanically evoked EMGMechanically evoked EMG
• Continuous, real-time EMG monitoring
• Indicates nerve root stretching,
compression and irritation
• Provides surgeon with immediate
information about MOTOR pathways
Mechanically evoked EMG from anterior tibialis muscle during L5 root palpation
Motor evoked potentials Motor evoked potentials -- EMGEMG
• Stimulate scalp with current
• Record from muscle groups below
surgical level
• Note changes in MOTOR pathway
EMG recording electrodes
Pedicle Screw Stimulationwith EMG Monitoring
Pedicle Screw StimulationPedicle Screw Stimulationwith EMG Monitoringwith EMG Monitoring
What are pedicles?What are pedicles?
Pedicle ScrewsPedicle Screws
• Metal screws that are driven
through the pedicle into a vertebral
body from the posterior side
• Form anchors to connect rods and
plates to other vertebrae
Scoliosis Corrected
Preoperative Postoperative
Lateral wall breach
Stimulating probe
Cathode (-)
Pedicle Screw Stimulation
Pedicle screw
Current returnAnode (+)In muscle
Brain Tumor ResectionEpilepsy Surgery
Brain Tumor ResectionEpilepsy Surgery
Motor Strip MappingMotor Strip Mapping
• Variation of somatosensory evoked
potentials
• Stimulate nerves at the wrist
• Identifies motor and sensory areas
of the cerebral cortex
1
2
3
4
Motor Strip MappingMotor Strip Mapping
5
Functional Cortical MappingFunctional Cortical Mapping
• Stimulate cortex directly
• Record evoked movements
• Note changes in language function
ASHA Ad Hoc Committee on Advanced in Clinical PracticeNeurophysiologic Intraoperative Monitoring
It is the position of the American Speech-Language-Hearing Association (ASHA) that neurophysiologic intraoperativemonitoring is within the scope of practice of audiologists with the appropriate knowledge base and skills. The purpose of neurophysiologic intraoperative monitoring is to assist surgeons to minimize or avoid altogether the occurrence of intraoperativeinjury to neural structures at risk due to the nature of the pathology and their proximity to the surgical field.
The practice of neurophysiologic intraoperative monitoring by an audiologist requires knowledge in neuroanatomy and neurophysiology, with special emphasis in neurodiagnostictechniques and their intraoperative applications. In addition, familiarity with the surgical procedure, effects of surgical manipulations and pharmacologic agents on neurophysiologic events, and the ability to recognize those events also is required.
If practitioners choose to perform these procedures, indicators should be developed, as part of a continuous quality improvement process, to monitor and evaluate the appropriateness, efficacy, and safety of the procedure conducted.
“Audiologists administer and interpret electrophysiologic
measurements of neural function including, but not limited to,
sensory and motor evoked potentials, tests of nerve
conduction velocity, and electromyography. These
measurements are used in differential diagnosis, pre- and
postoperative evaluation of neural function, and
neurophysiologic intraoperative monitoring of central nervous
system, spinal cord, and cranial nerve function.”
AAA Response to the AMA Scope of Practice Data Series: Audiologists -October 2009
Proposed Wording (version 1.0) in Scope of Practice
Audiologists are trained to administer and interpret
electrophysiological measurements of neural function
following stimulation of the auditory and vestibular sensory
pathways. Additionally, audiologists are also trained in the
use of electrophysiological measures to assess facial nerve
function. These same techniques may be employed in the
operating room (OR), and Intensive Care Unit (ICU)
settings to assess the physiological integrity of related
nervous system structures.
These measurement techniques include but are not limited
to the auditory brainstem response (ABR),
electrocochleography (ECochG), direct VIIIth nerve
recordings and vestibular evoked myogenic potentials
(VEMP), auditory evoked potentials including the ABR, the
auditory middle latency response (AMLR) and auditory late
response (ALR) following electrical stimulation of the
auditory pathway ( in cochlear implant recipients, and
candidates), and neurophysiological evaluation of facial
nerve function.
In addition to these activities, audiologists may be engaged
in neurophysiological intraoperative monitoring efforts that
are designed to help preserve the physiological integrity of
motor cranial nerves (e.g., CN III, IV, V, VI, VII, IX, X, XI, XII)
that are at risk for damage during various neurosurgical and
neurotological surgeries.
It is not the intention of the Academy to limit IOM performed by audiologists to the above modalities, however, audiologists who are engaged in neurophysiological monitoring activities outside of those mentioned above, (e.g. spinal cord function monitoring, peripheral nerve monitoring, monitoring for Parkinson's d., cortical localization) are encouraged to seek credentialing either through local privileging (for medical centers and hospitals), or, from other professional societies that credential non-physician providers (e.g. American Board of Neurophysiological Monitoring), as the Academy as an organization is not considered to be qualified to assess knowledge and skills in those IOM procedures.
The future of audiology?The future of audiology?
Audiology TechAudiology Tech for a local medical group in the for a local medical group in the NW San Antonio area:NW San Antonio area:
The job duties includeThe job duties include::
Basic Basic AudiologicAudiologic testing to include: testing to include:
Pure Pure ToneAudiometryToneAudiometry, , TympanometryTympanometry, ,
Vestibular assessment and VEMP testing.Vestibular assessment and VEMP testing.
The future of audiology?The future of audiology?
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Is Is intraoperativeintraoperative monitoringmonitoringin your future?in your future?
Training opportunities?Training opportunities?
American Societyof Neurophysiological Monitoring
www.asnm.org