Certified Neurophysiologic
Intraoperative Monitoring (CNIM)
Practice Exam
SECTION 1: INSTRUMENTATION & ELECTRICAL SAFETY (Q1-15)
Q1. Chassis leakage (the leakage current flowing from the instrument case to
ground) must be less than _____ under National Fire Protection Association
(NFPA) and AAMI standards.
A. 10 µA
B. 100 µA
C. 500 µA
D. 1000 µA
Correct Answer: B
Rationale: NFPA and AAMI standards require chassis leakage to be less than 100
µA. This ensures patient and staff safety from electrical shock in the OR
environment .
Q2. Maximum leakage current to the patient (through applied electrodes)
must be less than:
A. 10 µA
B. 100 µA
,C. 500 µA
D. 1 mA
Correct Answer: A
Rationale: Leakage current to the patient must be less than 10 µA to prevent
microshock hazards, particularly important for patients with indwelling conductive
pathways .
Q3. Differential input impedance of a quality intraoperative monitoring
amplifier should be:
A. 10 kΩ
B. 1 MΩ
C. 10 MΩ
D. 100 MΩ
Correct Answer: D
Rationale: High input impedance (100 MΩ) minimizes signal loss and ensures
accurate measurement of biological signals by preventing current flow through the
amplifier input .
Q4. What is the combined effect of resistance and reactance in an electrical
circuit?
A. Impedance
B. Capacitance
C. Conductance
D. Inductance
Correct Answer: A
Rationale: Impedance is the combined effect of resistance (opposition to DC
current) and reactance (opposition to AC current from capacitance or inductance) .
,Q5. What is the required common mode rejection ratio (CMRR) for
intraoperative monitoring amplifiers?
A. 100:1 (40 dB)
B. 1000:1 (60 dB)
C. 10,000:1 (80 dB)
D. 100,000:1 (100 dB)
Correct Answer: C
Rationale: CMRR must be at least 10,000:1 (80 dB). This allows the amplifier to
reject common mode signals (like 60 Hz interference) while amplifying differential
biological signals .
Q6. The minimum acceptable bandpass for intraoperative monitoring
amplifiers is:
A. 0.1-1,000 Hz
B. 0.1-15,000 Hz
C. 1-10,000 Hz
D. 10-15,000 Hz
Correct Answer: B
Rationale: The minimum bandpass for intraoperative monitoring amplifiers is 0.1-
15,000 Hz to accommodate both low-frequency EEG and high-frequency evoked
potential components .
Q7. What should be the ratio of high to low frequency filter settings to
minimize filter-induced phase shift?
A. 10:1
B. 50:1
, C. 100:1
D. 1000:1
Correct Answer: C
Rationale: A 100:1 ratio between high and low frequency filter settings minimizes
filter-induced phase shift, preserving waveform morphology and latency accuracy .
Q8. What effect does excessive low-frequency analog filtering have on evoked
potential peak latency?
A. Prolongs latency
B. Shortens latency
C. No effect on latency
D. Reverses polarity
Correct Answer: B
Rationale: Excessive low-frequency filtering (high-pass filtering) artificially
shortens peak latencies by removing the slow components that contribute to
waveform morphology .
Q9. Horizontal resolution in digital recording systems must have sampling
rates greater than:
A. 500 Hz
B. 5,000 Hz
C. 25,000 Hz
D. 50,000 Hz
Correct Answer: D
Rationale: Horizontal resolution requires sampling rates >50,000 Hz (<20 µs/data
point) to accurately capture high-frequency components of evoked potentials
without aliasing .
Intraoperative Monitoring (CNIM)
Practice Exam
SECTION 1: INSTRUMENTATION & ELECTRICAL SAFETY (Q1-15)
Q1. Chassis leakage (the leakage current flowing from the instrument case to
ground) must be less than _____ under National Fire Protection Association
(NFPA) and AAMI standards.
A. 10 µA
B. 100 µA
C. 500 µA
D. 1000 µA
Correct Answer: B
Rationale: NFPA and AAMI standards require chassis leakage to be less than 100
µA. This ensures patient and staff safety from electrical shock in the OR
environment .
Q2. Maximum leakage current to the patient (through applied electrodes)
must be less than:
A. 10 µA
B. 100 µA
,C. 500 µA
D. 1 mA
Correct Answer: A
Rationale: Leakage current to the patient must be less than 10 µA to prevent
microshock hazards, particularly important for patients with indwelling conductive
pathways .
Q3. Differential input impedance of a quality intraoperative monitoring
amplifier should be:
A. 10 kΩ
B. 1 MΩ
C. 10 MΩ
D. 100 MΩ
Correct Answer: D
Rationale: High input impedance (100 MΩ) minimizes signal loss and ensures
accurate measurement of biological signals by preventing current flow through the
amplifier input .
Q4. What is the combined effect of resistance and reactance in an electrical
circuit?
A. Impedance
B. Capacitance
C. Conductance
D. Inductance
Correct Answer: A
Rationale: Impedance is the combined effect of resistance (opposition to DC
current) and reactance (opposition to AC current from capacitance or inductance) .
,Q5. What is the required common mode rejection ratio (CMRR) for
intraoperative monitoring amplifiers?
A. 100:1 (40 dB)
B. 1000:1 (60 dB)
C. 10,000:1 (80 dB)
D. 100,000:1 (100 dB)
Correct Answer: C
Rationale: CMRR must be at least 10,000:1 (80 dB). This allows the amplifier to
reject common mode signals (like 60 Hz interference) while amplifying differential
biological signals .
Q6. The minimum acceptable bandpass for intraoperative monitoring
amplifiers is:
A. 0.1-1,000 Hz
B. 0.1-15,000 Hz
C. 1-10,000 Hz
D. 10-15,000 Hz
Correct Answer: B
Rationale: The minimum bandpass for intraoperative monitoring amplifiers is 0.1-
15,000 Hz to accommodate both low-frequency EEG and high-frequency evoked
potential components .
Q7. What should be the ratio of high to low frequency filter settings to
minimize filter-induced phase shift?
A. 10:1
B. 50:1
, C. 100:1
D. 1000:1
Correct Answer: C
Rationale: A 100:1 ratio between high and low frequency filter settings minimizes
filter-induced phase shift, preserving waveform morphology and latency accuracy .
Q8. What effect does excessive low-frequency analog filtering have on evoked
potential peak latency?
A. Prolongs latency
B. Shortens latency
C. No effect on latency
D. Reverses polarity
Correct Answer: B
Rationale: Excessive low-frequency filtering (high-pass filtering) artificially
shortens peak latencies by removing the slow components that contribute to
waveform morphology .
Q9. Horizontal resolution in digital recording systems must have sampling
rates greater than:
A. 500 Hz
B. 5,000 Hz
C. 25,000 Hz
D. 50,000 Hz
Correct Answer: D
Rationale: Horizontal resolution requires sampling rates >50,000 Hz (<20 µs/data
point) to accurately capture high-frequency components of evoked potentials
without aliasing .
