CNIM Motor Evoked Potentials (MEP)

Question 1

Transcranial electrical motor evoked potentials (tcMEPs) primarily monitor the integrity of which neural pathway?

Accepted Answer

Corticospinal tract

Answer

Dorsal column-medial lemniscal pathway

Answer

Spinothalamic tract

Answer

Vestibulospinal tract

Question 2

The D-wave in tcMEP monitoring is generated by:

Accepted Answer

Direct activation of corticospinal tract axons at the cortex

Answer

Muscle action potentials

Answer

Interneuronal activation in the spinal cord

Answer

Peripheral nerve compound action potentials

Question 3

What is the standard alarm criterion for tcMEP amplitude change during intraoperative monitoring?

Accepted Answer

50% amplitude decrease or complete loss

Answer

10% amplitude decrease

Answer

25% amplitude decrease

Answer

75% amplitude decrease

Question 4

Which muscle group is most commonly recorded for lower extremity tcMEP monitoring?

Accepted Answer

Tibialis anterior and abductor hallucis

Answer

Gastrocnemius only

Answer

Vastus lateralis only

Answer

Iliopsoas

Question 5

Why is total intravenous anesthesia (TIVA) preferred over volatile anesthetics for tcMEP monitoring?

Accepted Answer

Volatile agents cause dose-dependent suppression of tcMEP amplitudes

Answer

TIVA is cheaper

Answer

TIVA eliminates all muscle artifact

Answer

Volatile agents increase seizure risk from transcranial stimulation

Question 6

Neuromuscular blockade (NMB) should be avoided or minimized during tcMEP monitoring because:

Accepted Answer

Muscle relaxants reduce or abolish compound muscle action potential (CMAP) responses recorded from muscles

Answer

NMB increases stimulus artifact

Answer

NMB causes cortical spreading depression

Answer

Muscle relaxants interfere with cortical stimulation