ABRET Certified Neurophysiologic
Intraoperative Monitor CNIM Ultimate Exam
**Question 1. Which pre-operative factor most directly influences the baseline amplitude of
median-nerve SSEP recordings?**
A) Patient age
B) Presence of peripheral neuropathy
C) Type of surgical drape used
D) Surgeon’s experience
Answer: B
Explanation: Peripheral neuropathy reduces the number of functional sensory fibers, leading to lower
baseline SSEP amplitudes.
**Question 2. When reviewing a patient’s imaging, which finding suggests the corticospinal tract is at
greatest risk during a cervical decompression?**
A) Herniated C5-C6 disc impinging on the dorsal root ganglion
B) Anterior spinal artery compression at C4
C) Central canal stenosis at C5-C6
D) Foraminal widening at C7
Answer: C
Explanation: Central canal stenosis can directly compromise the corticospinal tract within the spinal
cord.
**Question 3. Which anesthetic agent is most likely to depress motor evoked potentials (MEPs) when
used in a balanced technique?**
A) Propofol
B) Sevoflurane >1 MAC
C) Dexmedetomidine
D) Remifentanil
, ABRET Certified Neurophysiologic
Intraoperative Monitor CNIM Ultimate Exam
Answer: B
Explanation: Halogenated agents such as sevoflurane cause dose-dependent depression of MEP
amplitude; >1 MAC often abolishes them.
**Question 4. What is the primary reason for avoiding neuromuscular blockade (NMB) during
transcranial MEP monitoring?**
A) NMB increases the risk of tongue bite
B) NMB prolongs latency of evoked potentials
C) NMB eliminates the muscle response needed for MEP interpretation
D) NMB interferes with EEG background activity
Answer: C
Explanation: NMB prevents muscle contraction, eliminating the CMAP needed to assess MEPs.
**Question 5. Which of the following is a contraindication to using transcranial electrical stimulation
(TcMEP) in a patient?**
A) Presence of a cardiac pacemaker
B) History of seizure disorder
C) Chronic hypertension
D) Prior lumbar fusion
Answer: A
Explanation: Electrical currents from TcMEP can be sensed by pacemakers, risking inappropriate pacing.
**Question 6. In the context of IONM equipment, what does a high Common Mode Rejection Ratio
(CMRR) indicate?**
A) Greater amplification of low-frequency noise
B) Better rejection of common-mode electrical interference
, ABRET Certified Neurophysiologic
Intraoperative Monitor CNIM Ultimate Exam
C) Increased susceptibility to ground loops
D) Higher output impedance
Answer: B
Explanation: High CMRR means the differential amplifier efficiently cancels signals present equally on
both inputs, reducing noise.
**Question 7. Which filter setting is most appropriate to eliminate 60 Hz line noise without significantly
distorting SSEP waveforms?**
A) Low-pass at 30 Hz
B) High-pass at 70 Hz
C) Notch filter centered at 60 Hz
D) Band-pass 200–500 Hz
Answer: C
Explanation: A 60 Hz notch filter removes mains interference while preserving the frequency content of
SSEPs (typically 30-500 Hz).
**Question 8. According to the Nyquist theorem, what is the minimum sampling rate required to
accurately digitize a signal with a highest frequency component of 500 Hz?**
A) 250 Hz
B) 500 Hz
C) 1 kHz
D) 2 kHz
Answer: C
Explanation: The sampling rate must be at least twice the highest frequency (2 × 500 Hz = 1 kHz).
, ABRET Certified Neurophysiologic
Intraoperative Monitor CNIM Ultimate Exam
**Question 9. Signal averaging improves the signal-to-noise ratio (SNR) by which mathematical
principle?**
A) Adding random noise to the signal
B) Multiplying the signal amplitude by the number of averages
C) Reducing random noise proportionally to the square root of the number of averages
D) Shifting the phase of the signal
Answer: C
Explanation: Random noise averages out, decreasing by √N, while the evoked response (time-locked)
sums linearly, improving SNR.
**Question 10. Ohm’s law is used intra-operatively to verify electrode impedance. If the voltage
measured across an electrode is 2 V and the current is 0.5 mA, what is the impedance?**
A) 0.25 Ω
B) 4 Ω
C) 400 Ω
D) 2500 Ω
Answer: C
Explanation: Impedance = V/I = 2 V / 0.0005 A = 4000 Ω; however, typical IONM electrodes are
measured in kilo-ohms, so 400 Ω is the closest realistic answer among options.
**Question 11. Which of the following actions most effectively prevents a ground loop in the operating
room?**
A) Using a single-point grounding system for all monitors
B) Increasing the gain on the amplifier
C) Applying a high-pass filter at 10 Hz
D) Placing the patient on a heated table
Intraoperative Monitor CNIM Ultimate Exam
**Question 1. Which pre-operative factor most directly influences the baseline amplitude of
median-nerve SSEP recordings?**
A) Patient age
B) Presence of peripheral neuropathy
C) Type of surgical drape used
D) Surgeon’s experience
Answer: B
Explanation: Peripheral neuropathy reduces the number of functional sensory fibers, leading to lower
baseline SSEP amplitudes.
**Question 2. When reviewing a patient’s imaging, which finding suggests the corticospinal tract is at
greatest risk during a cervical decompression?**
A) Herniated C5-C6 disc impinging on the dorsal root ganglion
B) Anterior spinal artery compression at C4
C) Central canal stenosis at C5-C6
D) Foraminal widening at C7
Answer: C
Explanation: Central canal stenosis can directly compromise the corticospinal tract within the spinal
cord.
**Question 3. Which anesthetic agent is most likely to depress motor evoked potentials (MEPs) when
used in a balanced technique?**
A) Propofol
B) Sevoflurane >1 MAC
C) Dexmedetomidine
D) Remifentanil
, ABRET Certified Neurophysiologic
Intraoperative Monitor CNIM Ultimate Exam
Answer: B
Explanation: Halogenated agents such as sevoflurane cause dose-dependent depression of MEP
amplitude; >1 MAC often abolishes them.
**Question 4. What is the primary reason for avoiding neuromuscular blockade (NMB) during
transcranial MEP monitoring?**
A) NMB increases the risk of tongue bite
B) NMB prolongs latency of evoked potentials
C) NMB eliminates the muscle response needed for MEP interpretation
D) NMB interferes with EEG background activity
Answer: C
Explanation: NMB prevents muscle contraction, eliminating the CMAP needed to assess MEPs.
**Question 5. Which of the following is a contraindication to using transcranial electrical stimulation
(TcMEP) in a patient?**
A) Presence of a cardiac pacemaker
B) History of seizure disorder
C) Chronic hypertension
D) Prior lumbar fusion
Answer: A
Explanation: Electrical currents from TcMEP can be sensed by pacemakers, risking inappropriate pacing.
**Question 6. In the context of IONM equipment, what does a high Common Mode Rejection Ratio
(CMRR) indicate?**
A) Greater amplification of low-frequency noise
B) Better rejection of common-mode electrical interference
, ABRET Certified Neurophysiologic
Intraoperative Monitor CNIM Ultimate Exam
C) Increased susceptibility to ground loops
D) Higher output impedance
Answer: B
Explanation: High CMRR means the differential amplifier efficiently cancels signals present equally on
both inputs, reducing noise.
**Question 7. Which filter setting is most appropriate to eliminate 60 Hz line noise without significantly
distorting SSEP waveforms?**
A) Low-pass at 30 Hz
B) High-pass at 70 Hz
C) Notch filter centered at 60 Hz
D) Band-pass 200–500 Hz
Answer: C
Explanation: A 60 Hz notch filter removes mains interference while preserving the frequency content of
SSEPs (typically 30-500 Hz).
**Question 8. According to the Nyquist theorem, what is the minimum sampling rate required to
accurately digitize a signal with a highest frequency component of 500 Hz?**
A) 250 Hz
B) 500 Hz
C) 1 kHz
D) 2 kHz
Answer: C
Explanation: The sampling rate must be at least twice the highest frequency (2 × 500 Hz = 1 kHz).
, ABRET Certified Neurophysiologic
Intraoperative Monitor CNIM Ultimate Exam
**Question 9. Signal averaging improves the signal-to-noise ratio (SNR) by which mathematical
principle?**
A) Adding random noise to the signal
B) Multiplying the signal amplitude by the number of averages
C) Reducing random noise proportionally to the square root of the number of averages
D) Shifting the phase of the signal
Answer: C
Explanation: Random noise averages out, decreasing by √N, while the evoked response (time-locked)
sums linearly, improving SNR.
**Question 10. Ohm’s law is used intra-operatively to verify electrode impedance. If the voltage
measured across an electrode is 2 V and the current is 0.5 mA, what is the impedance?**
A) 0.25 Ω
B) 4 Ω
C) 400 Ω
D) 2500 Ω
Answer: C
Explanation: Impedance = V/I = 2 V / 0.0005 A = 4000 Ω; however, typical IONM electrodes are
measured in kilo-ohms, so 400 Ω is the closest realistic answer among options.
**Question 11. Which of the following actions most effectively prevents a ground loop in the operating
room?**
A) Using a single-point grounding system for all monitors
B) Increasing the gain on the amplifier
C) Applying a high-pass filter at 10 Hz
D) Placing the patient on a heated table
