The Usefulness of Multimodal Intraoperative Neurophysiologic Monitoring During Brain or Spine Surgeries
Phase: NA
Conditions: Spine Condition
Sponsor: Alexandria University

USEFULNESS OF MULTIMODAL INTRAOPERTIVE
NEUROPHYSIOLOGIC MONITORING DURING DIFFERENT
NEUROSURGICAL OPERATIONS
NCT number:
Document Date : 18 November 2021

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USEFULNESS OF MULTIMODAL INTRAOPERTIVE
NEUROPHYSIOLOGIC MONITORING DURING DIFFERENT
NEUROSURGICAL OPERATIONS
باصعلأاو خمل ة ح ا ر ج تايلمع ءانثأةددعتمل ةيبصعلةيجولويسفلةبقارمل ةدئاف
هفلتخم
ل
Protocol of a thesis submitted
to the Faculty of Medicine
University of Alexandria
In partial fulfillment of the
requirements of the degree of
Doctorate Degree of Physical
Medicine, Rheumatology and
Rehabilitation
ةمدقم ثحب ةطخ
بطلةليكلةيردنكسإلا
ةعماج ايئزج ءافيإ
ة ج ر د ىلع لوصحل طورشل
يعيبطلبطليف ةاروتكدل
ليهأتلاو مزيتامورلو
نم
By
Ahmed Mosaad Mohamed Arafa
Elsakka
Master degree, Alex.
Demonstrator in
Department of Physical Medicine
Rheumatology and Rehabilitation
اقسلهفرعدمحم دعسم دمحأ يعيبطل
بطلريتسجام ةيردنكسإلا، ليهأتلاو
مزيتامورلاو ديعم
يعيبطلبطلمقسبليهأتلو
مزيتامورلو
بطلةيلك
ةيردنكسإلاةعماج
Faculty of Medicine
University of Alexandria

3
2021
2021
INTRODUCTION
Neurosurgical procedures for lesions placed in or close to eloquent areas
carry increased risk of neurological deficits, such as dysarthria, aphonia, paralysis
and paresthesia. Therefore, neurophysiological monitoring is essential for almost
all operations in or around eloquent locations of the brain and spine. (1)
Intraoperative neurophysiological monitoring (IONM) is the use of
electrophysiological methods to define eloquent neural structures and to monitor
their functional integrity during the surgery and provide information to surgeon
to prevent permanent neural injury due to surgical interventions. In most
neurosurgical procedures, IONM is a valuable and beneficial method for
monitoring the integrity of neural structures at risk. It provides simultaneous
neural information throughout the surgery. (2)
Using different modalities of IONM can aid in neurological recovery and
prevent damage . (3,4)
Somatosensory-evoked potentials (SSEPs) test the sensory pathways that
ascend through the dorsal column of the spinal cord, so normal SSEPs does not
exclude motor pathway injuries. Therefore, SSEPs are often supplemented with
motor-evoked potentials (MEPs). (5)
Stimulating needle electrodes are placed at the wrist and ankle for the
evaluation of the median and tibial nerves, respectively and SSEPs are recorded
using electrodes over the scalp. A warning signal is generally issued when there
is a 50% decrease in amplitude or 10% increase in latency compared with baseline
values.
(6)

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SSEPs signal changes, however, are not always related to a postoperative
neurological deficit. The specificity of SSEP during IONM was reported as 27%,
whereas the sensitivity was 99%. (7) The use of SSEPs is advantageous because it
does not provoke unwanted movement of the patient during surgery; and it is
easily quantifiable. (8)
Transcranial Motor Evoked Potential (tcMEP) is recognized as the most
sensitive technique compared with SSEP.(8) It monitors the corticospinal pathway
and aids in early detection of neurological dysfunction. (9-11) Trans cranial
electrical stimulation via electrodes placed on the scalp over the motor cortex area
is usually employed for the generation of MEPs and hence stimulation of the
corticospinal tract. A short train of 5-7 electrical pulse stimuli with high frequency
are usually used because it can generate action potential more easily through the
summation of the excitatory postsynaptic potentials. MEPs can be recorded over
muscle (Tc-mMEP) or over the spinal cord (D and I waves). Of these, Tc-mMEP
seems to be the most widely adopted approach because of the relative simplicity
of generating and recording MEPs. (8)
MEP amplitude decrements >50% of baseline values were considered
indicative of significant change, provided that the levels of neuromuscular
blockade and general anesthesia were unchanged. (12) MEP can also detect
hemodynamic changes like hypotension changes, positioning change and spinal
cord or roots compression. Only few studies report the alarm criteria of MEP or
SSEP for decompression surgeries. (13)
Propofol causes less suppression of MEP than inhalational agents.
Consequently, propofol and opioid total intravenous anesthesia (TIVA) is widely
recommended in intraoperative monitoring. (13)
Deepening anesthesia and
administering boluses reduces or obliterates muscle MEPs, whereas lightening
anesthesia increases them. Stable anesthesia is desirable, but adjustments may be
medically indicated and it is necessary to track them. Short acting neuromuscular

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blockade is often used to aid intubation of the patient during induction of
anesthesia. (13)
In addition, Free-running Electromyography (EMG) has been used as a real-
time monitoring modality to complement SSEP and tcMEP. (8) It detects
mechanical and/or metabolic irritation of the nerve. It can be recorded in the
innervated muscles without electrical stimulation of the nerve. (8)
Two types of discharge, each with different clinical significance, can be
observed using free-running EMG monitoring: tonic discharge and phasic
discharge. Tonic discharge consists of repetitive and steady episodes of activity
from grouped motor units that can last from several seconds to minutes; it can be
observed in nerve ischemia due to traction, heat spread from electro cautery, or
irrigation with saline. In contrast, phasic (burst) discharge is a short and relatively
synchronous burst of motor unit potentials, which is mostly associated with blunt
mechanical trauma. (8)
The old version of intraoperative assessment, wake-up test, might be
occasionally carried out when traditional neurophysiologic monitoring is not
available. In this procedure, the patient is awakened on the surgery table, with the
wound still open and the patient intubated. Narcotics are used to relieve pain.
When sufficiently awake, the patient is instructed loudly to move each extremity
to detect if there is injury of spinal cord. Problems can occur if the patient is too
confused to cooperate, or if the patient becomes agitated, he might move on the
table, extubate himself, knock out intravenous lines, or cause other difficulties,
Awakening of patient also may increase blood pressure of patient and cause
excessive bleeding. (14)
Universally IONM is mandatory now in correction surgery for spinal
deformities with high sensitivity and specify in detecting deficit. (15) IONM of
MEP in deformity surgeries can be focused during the time of maximal

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manipulation of neural elements, such as during screws insertion and correction.
In contrast, during decompression for cervical myelopathy, the risk to the spinal
cord and nerve roots exists throughout the entire decompression procedure and
not during a defined short period. (9) Moreover, the risk may be present even
before the procedure during positioning of the patient’s neck during intubation.
Despite that, the indications for monitoring in cervical decompression surgeries
are still controversial. (3,16) Some advocate its use (9-11) while others argue against.
(3,16)
To use only a single modality is not enough for a successful and efficient
neuromonitoring in neurosurgery. It has been shown that multimodal monitoring
has a high specificity and sensitivity in detecting postoperative neurological
injury.(17) Therefore, it is suggested to use appropriate multimodal intraoperative
neuromonitoring techniques for various surgeries to avoid any neurological
damage.

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AIM OF THE WORK
1. To assess the usefulness of applying appropriate different neuromonitoring
modalities in various neurosurgical operations with high risks of neural injury
2. To enhance our clinical experience and technical skills on various
neuromonitoring techniques.

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SUBJECTS
Twenty five patients with different brain or spine lesions will be admitted to
Neurosurgery Department in
Alexandria Main university hospital and are
scheduled to undergo surgery under Intraoperative neurophysiological
monitoring. Multimodal neuromonitoring techniques such as Somatosensory-
evoked potentials (SEP), transcranial electrical stimulation–motor-evoked
potentials (TES-MEP) , Free-running, Triggered Electromyography (EMG) and
electromyographic monitoring of different cranial nerves will be used during the
operation.
Inclusion criteria:
All patients will meet the following inclusion criteria:
1) Adults > 18 years
2) Brain or spine lesion close to eloquent area indicated for neuromonitoring.
3) Magnetic Resonance Image (MRI) for the site of lesion reflecting neural
injury risks.
Exclusion criteria:
1) presence of vascular clips, intracranial electrodes, pacemakers, other
implanted bio-mechanical equipment, cortical lesions, skull defects,
increased
intracranial
pressure,
and
history
of
epilepsy

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METHODS
Preoperative assessment:
All patients will be subjected to the following:
1- Clinical Examination including history taking, symptoms & signs.
2- Complete neurological examination.
4- All patients will be consented for Intraoperative neurophysiological
monitoring (IONM) as a part of the surgical informed consent process.
Intraoperative Procedures:
Anesthesia
Total intravenous anesthesia (TIVA protocol) will be used: Induction of
anesthesia will be performed with fentanyl 1 μg/kg and propofol 2 mg/kg
intravenous, followed by a short acting muscle relaxant such as succincyl
choline to facilitate tracheal intubation. Anesthesia will be maintained with
50% oxygen in air and propofol infusion. The infusion starts at 12 mg/kg/h
and then decreased gradually to 6–10 mg/kg/h. The infusion rate is then
adjusted according to hemodynamic responses to maintain a mean arterial
pressure (MAP) between 60 and 70 mmHg. (19)
Monitoring Technique
Multimodal IONM (MIONM) for different pathologies will include SSEP and
TES-MEP for spinal and cranial operations and free-run, triggered EMG
would be used for brainstem operations in which cranial nerves were at risk.
Monitoring Technique ISIS IOM Neuromonitoring System (Inomed,
Emmendingen, Germany) will be used for MIONM procedure. Monitoring
will
be
throughout
the
surgery.

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Monitoring will be divided into 3 stages: pre baseline, baseline, and
monitoring.
Pre baseline includes period from patient’s arrival to the operation room to
baseline recordings. It will take about 40 minutes long and allow us to check
the system and signal. This time covers equilibration of the anesthetics and
elimination of muscle relaxants used for induction, which cause variability in
recorded signals. (20)
Baseline is the period just before the high-risk manipulation of surgeon.
Baseline data will be recorded and used as reference in monitoring period
during the rest of the surgery. (20)
Anesthesia will be maintained by total intravenous anesthesia. Muscle
relaxants will be used only for intubation and then will not be administered
again except in cases that will require monitoring, which does not include MEP
and EMG. (21)
Transcranial Motor evoked potentials monitoring:
TcMEPs will be performed using transcranial stimulator over cortical
motor area. The electrodes will be placed over the motor cortical regions at C3
and C4 (International 10-20 system of electrode placement)(Appendix I). The
stimulation will be delivered with a train of 4-7 square wave pulses (75 μs
duration) while maintaining the inter-stimulus interval (ISI) at 2 msec.
Stimulation intensity will be started at 150 Volts and increased by 20 Volts
increments until robust response is obtained from several muscles. (22)
The tcMEPs will be recorded by a pairs of needles inserted in target
muscles. Target muscles in the upper extremity will be deltoid (axillary nerve,
C5-C6), biceps (musculocutanouse nerve, C5-C6), triceps (radial nerve, C7),
abductor pollicis brevis (APB) (C8-T1) and trapeziuses (C4) when needed if

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the level is above C4. In the lower extremity, tibialis anterior (TA), abductor
halluces (AH) and extensor digitorum brevis (EDB). (22)
Somatosensory evoked potential monitoring
SSEPs will be elicited by the stimulation of the posterior tibial nerve at
the ankle and median nerve at the wrist region. The cortical potentials of SSEP
will recorded from CP3 (2 cm behind C3) and CP4 (2 cm behind C4) in the
upper extremities and CPz (2 cm behind CZ)/Fz in the lower extremities
(depending on the 10–20 international electrode system). (23)
The stimulation will be delivered by alternating stimulation of the
posterior tibial nerve or the median nerve sites using biphasic 200 μsec square
wave pulses at a rate of 2.66/sec and intensity of 12-16 mA at median nerve
& 40-60 mA at posterior tibial nerve. Each average consists of about 200 trials
and with a band pass of 30–1000 Hz.(23)
Spontaneous Electromyography
free running EMG will be monitored from all the recording muscles of the
upper and lower limbs involved in the surgical level.
Baseline readings will be obtained before skin incision. SSEP will be analyzed
for latency and peak-to-peak amplitude and MEP will be analyzed for
amplitude and threshold. Stimulation will be alternated between SSEP and
MEP in continuous order while free running EMG will be performed
throughout surgery. The surgical team will be immediately informed of any
significant
IONM
changes.
(24)

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EMG Monitoring of Cranial Nerves
One pair of needle electrodes 1.5 cm apart from each other will be inserted
to orbicularis oris and one pair to orbicularis oculi muscles for monitoring facial
nerve functions. Another pair of needle electrodes will be inserted to masseter
muscle for trigeminal nerve monitoring. For hypoglossal nerve monitoring ,
needle electrodes will be inserted to lateral site of tongue. For both
glossopharyngeal and vagus nerves monitoring also needle electrodes will be
placed to posterior wall of pharynx. Impedances of all electrodes should be below
2 kO. Direct electrical stimulation of nerves will be performed using bipolar hand
probe to localize and find the trace of the nerve. Both free run EMG and triggered
EMG of cranial nerves will be used.(25)
Post operative evaluation :
• Full clinical neurological examination to asses any superadded neurological
deficit

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ETHICS OF RESEARCH
Research on human or human products:
Prospective study: Informed consent will be taken from patients. In case of
incompetent patients the informed consent will be taken from the guardians.
Retrospective study: Confidentiality of records will be considered
DNA / genomic material: Informed consent for DNA / genomic test and for
research will be taken from patients. No further tests will be carried out
except with further approval of committee and patients. If the samples will
travel outside Egypt the researcher will be responsible for transportation and
security approval.
All drugs used in the research are approved by the Egyptian Ministry of
Health
Research on animal:
The animal species are appropriate for the test.
After test, if the animal will suffer, it will be euthanized and properly
disposed.
After operation, it will have a proper postoperative care.

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RESULTS
The results will be tabulated and analyzed according to the different findings.

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DISCUSSION
Findings will be discussed in view of achievement of the aim of the study
and will be compared with similar studies in literature.

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APPENDIX I
FIGURE 1. Electrode positions on scalp for somatosensory evoked
potentials (SEP), motor-evoked potentials (MEP), and brainstem auditory–
evoked potentials (BAEP) monitoring.(26)

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