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“Patient Transparent” Intraoperative NeurophysiologicalMonitoring in Minimally Invasive Spine Surgery (MISS)

• Chief, Neurospine Surgery, California Spine Institute• Founding Chairman – President, the American Academy of Minimally

Invasive Spinal Surgery (AAMISMS). • Immediate past President of the International Society for Minimally

Intervention in Spine Surgery (ISMISS)• Internationally recognized pioneer and leader in minimally invasive

spinal surgery (MISS). • Interests:

– Promoting interdisciplinary, inter-specialty and international education– Research and Development in MIST

– Contribution in surgical informatics development of a “digital technological convergence and control system” for DOR (digital OR)

– Authored and co-authored numerous peer reviewed articles, chapters and textbooks, and appointed to editorial boards and an Editor-in-Chief for medical, surgical, and research journals.

• Enjoys the practice of martial arts (Grand Master, Martial Arts Hall of Fame and Martial Arts Legend Award)and its philosophy, playing Chinese classical musical instruments, collecting Asian Art, tennis, skiing, traveling and social networking.

• Contact Information: www.spinecenter.comJohn C Chiu, MD, DSc, FRCS (US)

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Society for Progress and Innovations for the Near East:

Updates and Cadaveric Bio-skills WorkshopBeirut, Lebanon

June 23 – 26, 2010

“Patient Transparent” Intraoperative

Neurophysiological Monitoring in Minimally Invasive Spine

Surgery (MISS)

John C Chiu, MD, DSc, FRCS (US)Chief, Neurospine SurgeryCalifornia Spine Institute

Thousand Oaks, California, USA

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Introduction

• Trend of spinal surgery is toward less or minimally invasive spine surgery (MISS)

• MISS aims at being less traumatic, with less morbidity and improved surgical outcome

• The obvious challenge of MISS is limited visualization and exposure of the relevant anatomy in spite of fluoroscopy and endoscopy to work with, and potentially placing the relevant neural structures at increased risk of trauma

• INTRAOPERATIVE NEUROPHYSIOLOGICAL MONITORING (IOM) of neural structure, direct visualization with fluoroscopy and endoscopy creates safer endoscopic MISS procedures

• Spontaneous EMG monitoring, at times SSEP and MEP can provide the surgeon with useful feedback to avoid neural trauma during MISS

• Intra-operative surface EEG/neurophysiological monitoring optimizes the anesthesia for MISS

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Introduction

• Different neural structures may be at risk during different stages of various spinal procedures

• In cases of pedicle screw placement, it can be monitored with triggered EMG, a longer probe can be used for stimulation, often through an expandable retractor

• Therefore, various customized intraoperative neurophysiological monitoring (IOM) instruments have been developed specifically for less or MISS to avoid neural trauma

• e.g. Synthes Oracle systems, NuVasive and Spineology ProMap™ active EMG neuro monitoring probe for EMG IOMare designed to alert the surgeon for instrument placement and to prevent neural trauma

• The real time IOM allows a surgeon to immediately intervene and correct potential irreversible neural damage

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Types of Intraoperative Neurophysiological Monitoring

(IOM)

For neurological complication avoidance!

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Spontaneous Electromyography (sEMG)

• Spontaneous EMG (sEMG) or Free-run EMG– Most frequently used for

endoscopic MISS related to microdecompression, of herniated disc, spinal nerve and stenosis decompression

– Continuous recording of muscle activity

– Mechanical or thermal nerve irritation causes EMG activity

• Triggered or Evoked EMG (tEMG)– Electrical stimulation through a

probe can activate nerve fibers in the surgical field causing a muscle response

– Used to identify nerve structures

– Used to test pedicle screws

Surgical Site EMG Recording

InjuryEMG Recording

EMG output

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Myotomal Distribution of Spinal Nerve for Neuro-monitoring

Root Muscle NerveC-3, C-4 trapezius CN XIC-5, (C-6) deltoid axillaryC-5, C-6 biceps brachii musculocutaneousC-6, C-7 triceps radial(C-8), T-1 abductor pollicis brevis MedianC-8, (T-1) abductor digiti minimi UlnarC-8, (T-1) adductor pollicis UlnarC-8, (T-1) first dorsal interosseus UlnarT-7–12 external obliqueT-7–12 rectus abdominisL-2, L-3, (L-4) iliacus lumbar plexus(L-2), L-3, L-4 vastus lateralis/medialis Femoral(L-2), L-3, L-4 rectus femoris Femoral(L-4), L-5, (S-1) semitendinosus/membranosus SciaticL-4, L-5 tibialis anterior PeronealL-5, (S-1) extensor hallucis peronealL-5, (S-1) extensor digitorum brevis peroneal(L-5), S-1 gastrocnemius lateral tibialS-1, (S-2) gastrocnemius medial tibialS-1, S-2 abductor hallucis tibialS-3, S-4, S-5 external anal sphincter pudendalS-3, S-4, S-5 external urethral sphincter pudendal

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Types of Mechanically Activated Spontaneous (sEMG)

• Spike Train: Repetitive series of spikes. Can be caused by stretching or compression of the nerve, heating or cooling

• Neurotonic Discharge: High frequency spike train discharge. Associated with nerve injury and post-op deficit

• Burst: High amplitude multiphasic complex transient. Bumping or cutting of nerve (cannot distinguish)

• Random Irregular: May indicate light anesthesia. No correlation to post-op deficit

Spike Train

Neurotonic Discharge

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Spontaneous Electromyography (sEMG)

1. Spike or burst activity indicates brief direct or indirect contact to a nerve and can assist the surgeon in navigating the instruments away from a particular trajectory

2. Spikes and bursts can also inform the surgeon of the instruments in proximity to the nerve root

3. During MISS, sEMG trains are of clinical significance, and the surgeon is typically notified if these occur

4. Trains are continuous, repetitive EMG firing often caused by continuous force applied to the nerve root

5. Trains of higher frequency and/or amplitude tend to represent significant nerve fiber recruitment caused by excessive force on the nerve and are likely to indicate a high probability of nerve injury if a relevant manipulation is sustained

6. These alerts a MISS surgeon for immediate corrective action or intervention to prevent irreversible neural trauma

IMPORTANT sEMG CLINICAL CORRELATION AND APPLICATION IN MISS

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Needle anode in the skin or muscle.

Alternate shoulder site can also be used.

Pedicle Screw Stimulation

• A breach in the pedicle allows current to reach the nerve root at a lower threshold

• Simple K-wire or active EMG neuro monitoring probe can be utilized to detect contact to the nerve

• To prevent neural trauma

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Threshold: > 10mA Good Value: Pedicle is intact

Threshold: > 8-10 mA Borderline Value: The pedicle wall and screw position should be re-examined.

Risk of breach is about 1/350

Threshold: > 6-8mA Cautionary Value: Possible breach or crack in pedicle wall. The pedicle wall should be re-examined and re-positioning of the screw should be considered.

Threshold: < 6 mA-3mA Poor Value: A Breached Pedicle is highly probable. Screw re-positioning or permanent screw removal may be necessary.

Threshold: ≤ 3 mA Severe Value: Direct nerve root contact is highly probable.

Criteria for Pedicle Screw Thresholds

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Somatosensory Evoked Potentials (SSEP)

• Spinal cord electrophysiological monitoring techniques arose in the 1970s, when SSEPs were described for monitoring the spinal cord during surgical deformity correction for scoliosis

• Measure of dorsal column sensory pathways

• Useful for – Spinal cord monitoring

– Detecting limb positioning problems

– Monitoring cortical perfusion

– Mapping sensory-motor cortical areas

• Alerts a surgeon for correction or intervention to prevent irreversible neural trauma

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SSEP Pathways

SSEPs are mediated through the dorsal columns in the spinal cord

Posterior Tibial

MedianNerve

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0 100 mS

C3’-C4’

Cz’-Fpz

Cs3-Fpz

LPF

Brainstem

Cortex

Cortex

Peripheral Nerve

Left Posterior Tibial Nerve (LPTN) – SSEP

Surgical Site

Injury InterventionInitiated

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Pre-op baseline PTN, SN, EMG & SSEP Response

Left Posterior Tibial Nerve Right Posterior Tibial Nerve

Left Saphenous Nerve Right Saphenous Nerve EEG

EMG

Monitoring Notes

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Thoracic cord injury

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Upper cervical cord injury

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Motor Evoked Potentials (MEP)

• Over the past 3 decades, MEPs have emerged as an extremely valuable and efficacious tool in IOM

• By the early 1990s, transcranial electrical stimulation was popularized as a method to monitor the corticospinal tracts

• MEPs have become the gold standard for IOM of the motor tracts

• The major drawback of MEP monitoring is inability to perform continuous monitoring

• Anesthetic inhalants decrease the efficacy

• Transcranial MEPs are the only “true motor tract” (separate blood supply) evoked potential

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100 mS

Epidural D-Wave

Muscle MEPs 20 mS

Transcranial Motor Evoked Potentials (TCMEP)

Electrical stimulation of motor cortex through the scalp

Record descending spinal cord potential (D-Wave)

Record limb muscle potentials

TCMEP

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TCMEP Changes During Lumbar Instrumentation

Baseline Rod Placement After Rod Removal

L Leg

R Leg

L Hand

R Hand

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Surface EEG Monitoring – BIS System

• Another important IOM:surface EEG - BIS (Bispectral Index) (Aspect Medical Systems, Newton, MA, USA) monitoringduring MISS

• Optimizes the depth of anesthesia

• BIS Index measures the level of consciousness of the patient and helps to decrease the amount of anesthetic medications used, up to 40% less

• Optimal IV conscious sedation with BIS Index range of 60-80

BIS index for anesthesia

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Clinical Application

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EMG Monitoring – Stimulation of K-wire

Adductor Longus

Vastus Medialis

Tibialis Anterior

Gastrocnemius

NERVE ROOT:

Response observed only on Vastus Medalis

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EMG Monitoring – Stimulation of K-wire

Adductor Longus

Vastus Medialis

Tibialis Anterior

Gastrocnemius

NERVE ROOT:

No Change in Stimulation intensity

only movement of location of K-wire

Response observed on ALL channels (muscles) resulting from movement of K-wire only

Simple K-wire or active EMG neuro monitoring probe can be utilized to detect contact to the nerveTo prevent neural trauma

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Case Illustration I

• 61 year old female with degenerative herniated lumbar discs and lumbar stenosis L4-5 with significant low back and leg pain and neurogenic claudication

• Under IV Conscious sedation and local anesthesia

• Underwent endoscopic microdiscectomy and inter spinal process decompression with an interspinous process spacer insertion

• IOM and BIS monitoring throughout her lumbar surgery

IOM Pre-op Baseline

Endoscopic Microdecompressive MISS for Lumbar Herniated Disc and Stenosis L4-L5

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Case Illustration I

IOM - EMG During Endoscopic Lumbar Discectomy

Neurotonic discharge changes in tracing, during placement of interspinous process spacer for distraction/decompression of Stenosis L4-L5 caused by retraction of Cauda Equina

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Case Illustration I

RPTN return to baseline. Patient awoke with no deficit.

IOM tracing RPTN returned to pre-spinal stenosis distractionstatus

Post Lumbar Surgery PTN, MN & EMG

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Endoscopic Lumbar MISS Surgery

• In lumbosacral spinal procedures, the focus on preservation of neurological function shifts to the nerve root level, as only the thecal sac and nerve roots are encountered below the level of the conus medullaris

• Endoscopic microdecompressive lumbar discectomies can be accomplished with simple sEMG IOM probe to prevent neural trauma

• Used concurrently, sEMG and SSEP monitoring are complimentary in preventing nerve root injury during lumbar spine surgery

• During surgery for release of a rare condition - tethered spinal cord, careful dissection and identification of the lumbosacral nerve roots by stimulation of various structures should be performed prior to relieving the tethering structure

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Lumbar Endoscopic MISS Case Illustration I

• 26 yo “Extreme Athlete”, Motorcycle, Rally car X-games gold medalist

• Severe posttraumatic L4-5 disc herniation

• Excellent relief from outpatient endoscopic MISS

• Return to rally car racing in two weeks

With sEMG IOM monitoring, successful endoscopic microdecompression for extruded herniated L4-5 disc

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Lumbar Endoscopic MISS Case Illustration II

With sEMG IOM monitoring, successful endoscopic microdecompression for large extruded herniated L5-S1 disc

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Lumbar Endoscopic MISS Case Illustration III

• Young grocery store manager

• One week post successful SMART endoscopic lumbar L4-5 discectomy aided by sEMG IOM

With sEMG IOM monitoring, successful endoscopic microdecompression for large extruded post traumatic herniated L4-5 disc

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Cervical and Thoracic MISS Surgery

• During microdecompressive cervical and thoracic discectomies and decompression of nerve root spinal procedures, nerve root/EMG monitoring is critically important to avoid trauma to spinal nerve

• Endoscopic microdecompressive cervical and thoracic discectomies can be accomplished with simple sEMG IOM probe to prevent neural trauma

• If the spinal cord is involved during procedures in the cervical and thoracic spine, preservation of spinal cord integrity is clearly of paramount importance

• As mentioned in the modalities section, the use of SSEPs and MEPs in combination is of great value in providing a global assessment of spinal cord function

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Cervical Endoscopic MISS Case Illustration IVWith sEMG IOM monitoring, 81 yo NS Professorunderwent successful endoscopic cervical discectomy, developedtransient extreme bradycardia (30) detectedand monitored on the large intra-op screen, of SurgMatix system and treated with atropine. Did well. Discharged in 1 hour.

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Cervical Endoscopic MISS Case Illustration V

With sEMG IOM monitoring English rock star had successful endoscopic cervical C3-4 discectomy for C3-4 disc herniation

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Thoracic Endoscopic MISS Case Illustration VI

27yr old F-22 fighter pilot suffered severe T7 herniated disc symptoms as a result of tremendous G-Force

T7 herniated disc

With sEMG IOM monitoring successful endoscopic thoracic MISS

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Discussion and Comment

• An advanced technologically driven MISS requires various less invasive surgical instruments and advanced complex technology than the usual traditional spinal surgery

• The MISS spine surgeon has only limited and restricted visualization of the surgical field

• MISS has to depend on the preoperative interpretation of pathology in relationship to X-Rays, MRI, CT, 3D CT imaging studies for pre surgical planning

• Intra-operatively C-Arm fluoroscopic imaging, and endoscopic visualization on real time basis facilitates the MISS

• It is aided by intraoperative neurophysiological monitoring especially with sEMG and other relevant neuro-monitoring modalities in order to avoid significant neurological complications

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Discussion and Comment

• SurgMatix® Is a “digital surgical technology convergence and OR control system”, involving monitoring and recording of all wave form and imaging data, including sEMG, Pre-Operative, Intra-Operative and Post-Operative phases of MISS

• Real time sEMG IOM integrates with all patient related medical/surgical information creates a “patient centric” and “patient transparent” DOR in order to facilitate a safer MISS

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Discussion and CommentSurgMatix intraoperative monitoring screen displays real time wave form, imaging, vital signs, sEMG, BIS, IOM information to facilitate MISS surgery

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Conclusion:

• Utilization of intraoperative neurophysiological monitoring, IOMprevents neurological injury andprovides a safer MISS

• A thorough familiarity with the various modalities available for IOM - including especially sEMG,and tEMG besides SSEPs, MEPs, is a must for a endoscopic MISSsurgeon

• Knowledge MISS technique, benefits and limitations of each monitoring modality helps to maximize the value of IOMduring MISS procedures

• An interdisciplinary approach to IOM facilitates the optimization of MISS technique and in preventing neural trauma

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Hope you enjoyed this presentation!

“Danke schön”

“Merci”“Gracias”

“Cám ón”

“Arigato”

“Thank you”

John C. Chiu, M.D., FRSC (US), D.Sc.

California Spine Institute

خيلی ممنون“ ”مرسی