Motor Evoked Potentials (MEP) Flashcards

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

Answer: Corticospinal tract

tcMEPs monitor the corticospinal tract (anterior and lateral funiculi of the spinal cord), which is responsible for voluntary motor control.

The D-wave in tcMEP monitoring is generated by:

Answer: Direct activation of corticospinal tract axons at the cortex

The D-wave results from direct (D) electrical activation of corticospinal axons at the initial segment, producing a fast-conducting descending volley recorded epidurally.

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

Answer: 50% amplitude decrease or complete loss

A 50% or greater decrease in tcMEP amplitude from baseline or complete loss is the widely accepted alarm criterion requiring surgical team notification.

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

Answer: Tibialis anterior and abductor hallucis

The tibialis anterior and abductor hallucis are the most commonly recorded lower extremity muscles for tcMEP monitoring due to their reliable cortical representation.

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

Answer: Volatile agents cause dose-dependent suppression of tcMEP amplitudes

Volatile anesthetic agents cause dose-dependent suppression of tcMEP amplitudes by inhibiting corticospinal tract activity and synaptic transmission in the spinal cord interneurons.

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

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

Neuromuscular blockade prevents neuromuscular junction transmission, reducing or abolishing the CMAPs recorded from muscles that constitute the tcMEP response.