Mixed Deck — All CNIM Topics Flashcards

Etomidate transiently increases SSEP amplitudes because it:

Answer: Decreases synaptic inhibition in the somatosensory cortex

Etomidate decreases cortical inhibitory activity (GABA modulation), temporarily enhancing cortical excitability and increasing SSEP amplitudes, which can be exploited therapeutically.

Pop and burst EMG patterns during free-running monitoring are considered:

Answer: Lower-risk, brief responses to transient mechanical contact

Pop and burst patterns are brief, transient EMG responses to mechanical contact (touching the nerve) that are lower risk than sustained neurotonic trains but still warrant alerting the surgeon.

During posterior fossa surgery, an isolated loss of Wave I with preserved Wave V most likely indicates:

Answer: Cochlear or distal nerve VIII injury

Isolated Wave I loss with preserved Wave V suggests peripheral cochlear or distal cranial nerve VIII injury rather than central brainstem involvement.

Electrical interference from the surgical cautery (electrosurgery unit) in EMG recordings is best managed by:

Answer: Having the surgeon temporarily stop cautery, noting the artifact, and confirming it does not persist after cessation

Electrocautery produces intense artifact; communicating with the surgical team to pause cautery use when EMG activity is observed confirms whether the activity is artifact or genuine nerve activity.

What is the standard electrode placement system used for intraoperative EEG monitoring?

Answer: 10-20 International System

The 10-20 International System is the universally accepted standard for scalp electrode placement in both routine and intraoperative EEG.

An increase in Wave V latency of more than 1 ms from baseline during posterior fossa surgery is considered:

Answer: A significant alarm criterion

An increase in Wave V latency of 1 ms or more from baseline is a widely accepted alarm criterion during posterior fossa surgery, indicating auditory pathway compromise.

What is the typical stimulation pulse duration used for median nerve SSEP in intraoperative monitoring?

Answer: 0.2 ms

A pulse duration of approximately 0.2 ms (200 microseconds) is standard for peripheral nerve stimulation during intraoperative SSEP monitoring.

What is the primary goal of continuous EEG monitoring during aortic arch surgery?

Answer: To monitor cerebral cortical activity and detect ischemia

Continuous EEG monitoring helps detect changes in cortical activity that may indicate ischemia or other complications.

Hemodilution during major surgery affects SSEP monitoring by:

Answer: Reducing SSEP amplitudes when hematocrit drops below critical oxygen delivery levels

Severe hemodilution reduces oxygen-carrying capacity; when hematocrit falls below critical levels, neural ischemia can cause SSEP amplitude reduction, requiring distinction from surgical injury.

What electrode impedance level is considered acceptable for reliable intraoperative EEG recording?

Answer: Less than 5 kΩ

Electrode impedances below 5 kΩ ensure good electrical contact, minimizing artifact and maintaining signal integrity in the OR environment.

What action should be taken if there is a sudden loss of TcMEPs during surgery?

Answer: Immediately notify the surgical team

In the context of IONM, 'baseline' refers to the initial neurophysiological recordings obtained after the patient is positioned and anesthetized, but before any significant surgical manipulation begins. These baseline signals serve as a crucial reference point against which all subsequent intraoperative changes are compared. Any significant deviation from the baseline during surgery indicates a potential neurological event.

The addition of 50% nitrous oxide to TIVA primarily affects MEP monitoring by:

Answer: Significantly reducing MEP amplitudes and increasing the risk of complete MEP loss

Adding 50% nitrous oxide to propofol TIVA significantly reduces MEP amplitudes, with the combined effect sometimes causing complete MEP loss and warranting avoidance during MEP monitoring.

During microvascular decompression (MVD) for hemifacial spasm, BAEP monitoring is used because:

Answer: The auditory nerve (CNVIII) runs adjacent to the facial nerve in the posterior fossa and can be injured during surgery

During MVD for hemifacial spasm, the auditory nerve runs near the facial nerve root entry zone; BAEP monitoring protects hearing by detecting auditory pathway compromise during dissection.

During spinal cord stimulator lead placement, EMG is used to:

Answer: Confirm lead position by recording paresthesia-mapping responses from stimulated myotomes

EMG can confirm spinal cord stimulator lead position by verifying that electrical stimulation activates the intended myotomes corresponding to the patient's pain distribution.

During carotid endarterectomy, which type of monitoring is most critical for assessing the functional integrity of the cortex?

Answer: Electroencephalography (EEG)

EEG is critical for assessing the functional integrity of the cortex by monitoring electrical activity in the brain.

The standard BAEP amplitude alarm criterion during intraoperative monitoring is:

Answer: 50% decrease in Wave V amplitude

A 50% or greater decrease in Wave V amplitude from baseline is the standard alarm threshold for BAEPs, complementing the 1 ms latency criterion.

Which factor can most significantly affect the quality of IONM signals?

Answer: Type of anesthesia used

A sudden loss or significant degradation of TcMEPs is an urgent finding indicating potential motor pathway compromise or injury. The immediate and appropriate action is to notify the surgical team without delay. This allows them to investigate the cause, adjust surgical maneuvers, or take other protective measures to prevent permanent neurological deficit, as delaying notification could lead to irreversible damage.

The absence of EMG activity in all monitored muscles during intraoperative free-running recording most likely indicates:

Answer: Possible residual neuromuscular blockade preventing reliable monitoring

Complete absence of any EMG activity, including no spontaneous potentials in a quiet field, may indicate residual NMB is blocking neuromuscular transmission and rendering EMG monitoring unreliable.

What type of EEG montage references each electrode to the mathematical average of all scalp electrodes?

Answer: Common average reference montage

The common average reference montage subtracts the mean signal of all scalp electrodes from each individual channel, minimizing bias from any single reference site.

The CNIM credential is awarded by which professional organization?

Answer: American Board of Registration of Electroencephalographic and Evoked Potential Technologists (ABRET)

The CNIM credential is administered and awarded by ABRET, the national credentialing body for EEG and evoked potential technologists.