ABRET CNIM-CS Specialist in IOM Complex Spine

Which spinal cord vascular structure most commonly supplies the anterior two-thirds of the thoracolumbar cord and is the principal concern during deformity correction?

• APosterior spinal arteries
• BAnterior spinal artery via the artery of Adamkiewicz
• CVertebral arteries
• DSegmental radicular veins

In a posterior spinal fusion for adolescent idiopathic scoliosis, which monitoring modality most directly assesses the corticospinal tract?

• ASSEP
• BTranscranial MEP
• CBAEP
• DFree-run EMG

Which anesthetic regimen is most compatible with reliable transcranial MEP monitoring during complex spine surgery?

• ASevoflurane 1.0 MAC plus rocuronium infusion
• BTotal intravenous anesthesia (TIVA) with propofol and remifentanil, no muscle relaxant af…
• CIsoflurane plus nitrous oxide and continuous vecuronium
• DKetamine bolus plus high-dose volatile agent

What is a commonly accepted MEP warning criterion during complex spine surgery for an all-or-none alarm?

• A30% decrease in amplitude
• BDisappearance of the CMAP response or sustained loss in target muscles
• C10% increase in latency
• DAny change in stimulation threshold

What SSEP warning criterion is most widely cited for complex spine cases?

• A20% amplitude decrease only
• B50% amplitude decrease or 10% latency increase from baseline
• CAny change beyond background variability
• DLoss of N20 only

A pedicle screw is stimulated with a constant-current monopolar probe. A triggered EMG response is obtained at 4 mA. What does this most likely indicate?

• AWell-positioned screw within bone
• BPossible medial pedicle wall breach
• CStimulator malfunction
• DExcessive sedation

The D-wave is best described as which of the following?

• AA late cortical SSEP component
• BThe direct corticospinal volley recorded epidurally after transcranial stimulation
• CAn EMG response from paraspinal muscles
• DA brainstem auditory wave

During an intramedullary spinal cord tumor resection, MEPs from the lower extremities are lost but the D-wave amplitude remains greater than 50% of baseline. What is the expected motor outcome?

• APermanent paraplegia
• BTransient motor deficit with substantial recovery expected
• CNo change
• DCortical blindness

Which muscle is most commonly chosen as a recording site for lower extremity MEPs in a thoracolumbar deformity case?

• ATibialis anterior and abductor hallucis
• BSternocleidomastoid
• COrbicularis oculi
• DDeltoid

A patient undergoing pedicle subtraction osteotomy (PSO) at L3 for fixed sagittal imbalance experiences sudden bilateral lower extremity MEP loss after closure of the osteotomy. What is the most appropriate immediate response?

• AContinue surgery; MEPs are unreliable
• BNotify the surgeon, raise mean arterial pressure, verify anesthesia and temperature, and…
• CIncrease volatile anesthetic to deepen anesthesia
• DWait 30 minutes for spontaneous recovery

Which biomechanical feature of pedicle subtraction osteotomy increases the risk of spinal cord ischemia?

• AAcute shortening of the spinal column
• BDistraction across multiple segments
• CLateral translation of the cord
• DUse of cobalt-chrome rods

Which combination of recording sites is appropriate for SSEPs during a posterior thoracolumbar fusion?

• ABilateral median nerve only
• BBilateral tibial nerve with cortical (Cz'-Fz) and subcortical (cervical) recordings, with…
• CPudendal nerve only
• DTrigeminal nerve only

During an anterior cervical discectomy and fusion (ACDF) at C5-C6, sudden unilateral C5 myotome MEP loss occurs after distraction. What is the most likely cause?

• AC5 nerve root traction or ischemia
• BCardiac arrest
• CVolatile anesthetic increase
• DBilateral SSEP shift

Which monitoring modality is most useful for detecting recurrent laryngeal nerve injury during anterior cervical exposure?

• AFree-run EMG from vocalis/thyroarytenoid via endotracheal tube electrodes
• BBAEPs
• CLower extremity SSEPs
• DD-wave

Which physiologic factor most commonly causes bilateral, gradual reduction in SSEP amplitude that mimics surgical injury?

• AHypothermia or systemic hypotension
• BUnilateral pedicle breach
• CSolo nerve root retraction
• DLocalized epidural hematoma

Which statement best describes free-run EMG during pedicle screw insertion?

• AIt detects neurotonic discharges suggestive of nerve root irritation
• BIt directly measures motor cortex output
• CIt quantifies dorsal column conduction
• DIt is a triggered modality only

Which transcranial electrical stimulation pattern is most commonly used to elicit reliable myogenic MEPs in complex spine surgery?

• ASingle pulse
• BTrain of 5-9 pulses with 1-4 ms interstimulus interval
• CContinuous low-frequency stimulation
• DMagnetic single-shock

Which structure is the principal generator of the cortical N20 SSEP response after median nerve stimulation?

• ABrachial plexus
• BPrimary somatosensory cortex (area 3b)
• CThalamus
• DCervical spinal cord

When using lateral flank position for an anterior thoracolumbar interbody fusion (XLIF/LLIF), which monitoring modality reduces the risk of lumbar plexus injury?

• ABAEP
• BTriggered EMG (directional discrete stimulation through dilator/probe)
• CD-wave alone
• DAuditory P300

Which factor most significantly increases pediatric MEP variability compared with adults?

• AHigher synaptic density and incomplete myelination of corticospinal tracts
• BLarger amplitudes than adults at all ages
• CLower stimulation thresholds at all ages
• DAbsent rolandic cortex

Which finding most specifically predicts permanent motor deficit during intramedullary tumor resection?

• ALoss of myogenic MEPs alone with preserved D-wave
• BLoss of D-wave amplitude greater than 50%
• CBilateral SSEP shift of 5%
• DBrief drop in blood pressure

Which MAP target is generally recommended during high-risk deformity correction to optimize spinal cord perfusion?

• AMAP 50-55 mm Hg
• BMAP 80-90 mm Hg or higher when signals are at risk
• CMAP 30-40 mm Hg
• DMAP is irrelevant

What is a typical SSEP latency change attributable to a 1 degree Celsius drop in core temperature?

• ANo change
• BApproximately 0.7-1 ms latency increase per degree
• C10 ms latency decrease
• DRandom change unrelated to temperature

Which monitoring strategy best detects ischemia during thoracic deformity correction with potential compromise to the artery of Adamkiewicz?

• ALower extremity tcMEPs combined with SSEPs and segmental EMG
• BBAEPs alone
• CMedian nerve SSEPs alone
• DVisual evoked potentials

Which intraoperative test confirms motor function when MEPs are unavailable or ambiguous?

• AStagnara wake-up test
• BLumbar puncture
• CEEG burst-suppression check
• DTCD ultrasound

Which intraoperative imaging tool can localize an intradural mass to guide myelotomy planning when combined with IOM?

• AIntraoperative ultrasound
• BMagnetoencephalography
• CPulse oximetry
• DCapnography

Which alarm criterion modification is most appropriate when a patient has very small or asymmetric baseline MEPs from preexisting myelopathy?

• AUse a 50% amplitude criterion identical to SSEPs
• BApply individualized criteria, document baseline, and alert on any reproducible degradati…
• CDiscontinue MEP monitoring
• DSwitch entirely to EEG

What is the typical anode position for transcranial MEP stimulation when monitoring left lower extremity?

• ARight hemisphere (over C4 region) anode
• BCz alone
• CInion
• DMastoid

Which complication should the IOM team be especially alert for during occipitocervical fixation?

• AVertebral artery injury and brainstem ischemia
• BFemoral nerve palsy
• CRecurrent laryngeal nerve injury
• DCauda equina syndrome

What is the appropriate first action when triggered EMG threshold from a thoracic pedicle screw is 5 mA in an awake-equivalent setting?

• AIgnore the result; thoracic pedicles are not at risk
• BNotify the surgeon; the screw may need redirection or replacement and confirmatory imagin…
• CIncrease stimulation to 50 mA and recheck
• DSwitch to BAEP monitoring

Which scenario most strongly favors adding D-wave monitoring to a complex spine case?

• ARoutine 1-level lumbar microdiscectomy
• BIntramedullary spinal cord tumor resection
• COutpatient cervical injection
• DStandalone pedicle screw revision under fluoroscopy

Which option best represents communication best practice when MEP loss is observed?

• AWait for surgeon to ask
• BUse closed-loop, time-stamped notification with the modality, location, magnitude, and ti…
• CEmail the surgeon after the case
• DInform only the circulating nurse

Which baseline waveform property is most important to document before the incision in a complex spine case?

• AReproducibility, amplitude, and latency for each modality at each recording site
• BHeart rate only
• CPatient weight only
• DSurgeon preference

Which factor reduces the reliability of triggered EMG for pedicle screw assessment?

• AUse of partial neuromuscular blockade
• BElectrode placement on the appropriate myotome
• CConstant-current stimulation
• DBipolar stimulation probe close to bone

Which physiologic perturbation typically improves SSEP amplitudes when corrected during spine surgery?

• AHypotension corrected to MAP greater than 80 mm Hg
• BHyperthermia
• CSevere acidemia
• DProfound hypocapnia

What is the role of bite blocks during MEP monitoring?

• APrevent tongue/lip laceration and dental damage from masseter contraction during stimulat…
• BReduce stimulation artifact
• CIncrease MEP amplitude
• DSubstitute for an oropharyngeal airway

Which laboratory abnormality is most likely to depress evoked potential amplitudes intraoperatively?

• ASevere anemia (hemoglobin less than 7 g/dL)
• BMild hyperkalemia
• CMild leukocytosis
• DSlight hypernatremia

Which IOM finding most specifically suggests a developing epidural hematoma after closure of a posterior thoracic instrumentation case?

• ASudden bilateral lower extremity SSEP and MEP loss after closure or in PACU monitoring
• BBilateral median nerve SSEP within normal range
• CStable upper extremity MEPs
• DReduced electromyography baseline before incision

Which pediatric consideration is critical when planning IOM for early-onset scoliosis surgery?

• AUse lower transcranial stimulation intensities and consider higher montage flexibility be…
• BPediatric patients tolerate volatile agents at high MAC for MEPs
• CDo not use TIVA in pediatric patients
• DPediatric MEPs require no anesthesia adjustment

Which step is most appropriate when an MEP signal change correlates with a recent rod-bending or compression maneuver?

• ANotify the surgeon immediately and request reversal or modification of the maneuver while…
• BContinue the maneuver and reassess after final tightening
• CIncrease the stimulation voltage and ignore the change
• DSwitch off MEPs and rely on visual inspection

Which technique increases the reliability of recording lower extremity MEPs in obese patients?

• AUse of subdermal needle electrodes placed close to the motor point and verification of im…
• BUse of standard surface electrodes only
• CIncreasing volatile anesthetic depth
• DAvoiding TIVA

Which structure is the dominant pathway assessed by the D-wave?

• ADorsal columns
• BFast-conducting corticospinal axons
• CSpinothalamic tract
• DReticulospinal tract

Which option best describes the rationale for multimodal monitoring during complex spine surgery?

• ADifferent modalities assess different tracts and increase sensitivity and specificity for…
• BMultimodal monitoring eliminates the need for the surgeon
• CIt reduces operative time
• DIt simplifies anesthesia

Which MEP change pattern most strongly suggests focal nerve root injury rather than corticospinal tract dysfunction?

• ALoss confined to a single myotome with preserved adjacent myotomes
• BBilateral, symmetric global MEP loss
• CGradual bilateral amplitude reduction
• DBilateral symmetric latency increase

Which transcranial MEP safety consideration is most relevant in patients with implanted cochlear or deep brain stimulator devices?

• ATES is generally contraindicated or requires careful risk-benefit discussion due to poten…
• BTES has no contraindications
• CTES is preferred over SSEPs in these patients
• DTES amplitude is unaffected by the implant

Which clinical feature most increases the risk of new neurologic deficit during deformity correction?

• ASevere rigid coronal/sagittal deformity with preexisting myelopathy
• BMild idiopathic scoliosis less than 30 degrees
• CPrior negative spine MRI
• DPatient age 25-35 years

Which intervention is appropriate when MEP signals deteriorate during prone-position surgery and air embolism is suspected?

• ANotify anesthesia, flood the field with saline, lower the head, and consider central aspi…
• BContinue the case and recheck signals at closure
• CStop monitoring
• DIncrease volatile anesthetic