CNIM Practice Exam Questions with
Verified Answers & Rationales 2026-2027
Question 1: An increase in stimulation intensity causes a linear increase in
which of the following SSEP components?
A) N20
B) N45
C) P31
D) P37
Correct Answer: C) P31
Rationale: As stimulation intensity increases, the amplitude of the P31
component of the SSEP increases linearly. The P31 is a far-field potential
generated in the brainstem. Other components like N20 and P37 are cortical
responses that may show a more complex relationship with stimulus
intensity.
Question 2: During a median nerve preoperative study, a patient has
discomfort at the wrist. Stimulation electrodes are 10 mm gold disk,
stimulus intensity is 20 mA, and stimulus duration is 100 μsec. Which of the
following would most likely reduce the patient's discomfort while
maintaining adequate stimulation?
A) Increase the stimulus intensity
B) Decrease the number of repetitions
C) Increase the stimulus duration
D) Change to needle electrodes
,Correct Answer: B) Decrease the number of repetitions
Rationale: Decreasing the number of repetitions reduces the total stimulation
time and can lessen patient discomfort while still allowing for adequate
signal averaging. Increasing stimulus intensity (A) would worsen discomfort.
Changing to needle electrodes (D) may increase discomfort.
Question 3: What is not an advantage of epidural recordings?
A) High signal-to-noise ratio
B) Absence of significant artifact
C) Ability to record from specific spinal tracts
D) Non-invasive placement
Correct Answer: D) Non-invasive placement
Rationale: Epidural recordings are invasive, requiring placement of electrodes
in the epidural space. They offer advantages such as high signal-to-noise
ratio (A), absence of significant artifact (B), and the ability to record from
specific spinal tracts (C), but they are not non-invasive.
Question 4: The stimulation rate is determined by the:
A) Stimulus intensity
B) Analysis time
C) Number of sweeps
D) Filter settings
Correct Answer: B) Analysis time
Rationale: The stimulation rate (frequency) is determined by the analysis time
(sweep length). A longer analysis time requires a slower stimulation rate to
,avoid overlapping responses. For example, a 100 ms sweep allows a
maximum rate of approximately 10 Hz.
Question 5: The lumbar potential is generated from:
A) Pre-synaptic responses
B) Post-synaptic responses
C) Axonal volleys
D) Cortical generators
Correct Answer: B) Post-synaptic responses
Rationale: The lumbar potential (LP) is generated from post-synaptic
responses in the spinal cord. It represents the activity of the dorsal horn
neurons in response to afferent input. The LP is a stationary potential that is
useful for monitoring spinal cord function.
Question 6: The P31 response to posterior tibial nerve stimulation:
A) Is recorded locally over the lumbar spine
B) Is recordable over a generalized region of scalp
C) Is generated in the peripheral nerve
D) Is a cortical response only
Correct Answer: B) Is recordable over a generalized region of scalp
Rationale: The P31 response to posterior tibial nerve stimulation is a far-field
potential that is recordable over a generalized region of the scalp. It is
generated in the brainstem and is not localized to a specific cortical area.
, Question 7: How many waves of a 60 Hz signal should you see in a 250 mS
sweep?
A) 10
B) 12
C) 15
D) 20
Correct Answer: C) 15
Rationale: At 60 Hz, one complete cycle takes 1/60 = 16.67 ms. In a 250 ms
sweep, the number of cycles is .67 = 15. This calculation is important
for identifying 60 Hz interference in evoked potential recordings.
Question 8: If the bin width of your system is 20 μS, what is the sampling
rate?
A) 5,000 Hz
B) 10,000 Hz
C) 20,000 Hz
D) 50,000 Hz
Correct Answer: D) 50,000 Hz
Rationale: Sampling rate = 1 / bin width = 1 / (20 μS) = 1 / (0.000020 s) =
50,000 Hz. This high sampling rate is necessary to accurately digitize high-
frequency components of evoked potentials without aliasing.
Question 9: Somatosensory evoked potentials are less reliable in patients
with:
Verified Answers & Rationales 2026-2027
Question 1: An increase in stimulation intensity causes a linear increase in
which of the following SSEP components?
A) N20
B) N45
C) P31
D) P37
Correct Answer: C) P31
Rationale: As stimulation intensity increases, the amplitude of the P31
component of the SSEP increases linearly. The P31 is a far-field potential
generated in the brainstem. Other components like N20 and P37 are cortical
responses that may show a more complex relationship with stimulus
intensity.
Question 2: During a median nerve preoperative study, a patient has
discomfort at the wrist. Stimulation electrodes are 10 mm gold disk,
stimulus intensity is 20 mA, and stimulus duration is 100 μsec. Which of the
following would most likely reduce the patient's discomfort while
maintaining adequate stimulation?
A) Increase the stimulus intensity
B) Decrease the number of repetitions
C) Increase the stimulus duration
D) Change to needle electrodes
,Correct Answer: B) Decrease the number of repetitions
Rationale: Decreasing the number of repetitions reduces the total stimulation
time and can lessen patient discomfort while still allowing for adequate
signal averaging. Increasing stimulus intensity (A) would worsen discomfort.
Changing to needle electrodes (D) may increase discomfort.
Question 3: What is not an advantage of epidural recordings?
A) High signal-to-noise ratio
B) Absence of significant artifact
C) Ability to record from specific spinal tracts
D) Non-invasive placement
Correct Answer: D) Non-invasive placement
Rationale: Epidural recordings are invasive, requiring placement of electrodes
in the epidural space. They offer advantages such as high signal-to-noise
ratio (A), absence of significant artifact (B), and the ability to record from
specific spinal tracts (C), but they are not non-invasive.
Question 4: The stimulation rate is determined by the:
A) Stimulus intensity
B) Analysis time
C) Number of sweeps
D) Filter settings
Correct Answer: B) Analysis time
Rationale: The stimulation rate (frequency) is determined by the analysis time
(sweep length). A longer analysis time requires a slower stimulation rate to
,avoid overlapping responses. For example, a 100 ms sweep allows a
maximum rate of approximately 10 Hz.
Question 5: The lumbar potential is generated from:
A) Pre-synaptic responses
B) Post-synaptic responses
C) Axonal volleys
D) Cortical generators
Correct Answer: B) Post-synaptic responses
Rationale: The lumbar potential (LP) is generated from post-synaptic
responses in the spinal cord. It represents the activity of the dorsal horn
neurons in response to afferent input. The LP is a stationary potential that is
useful for monitoring spinal cord function.
Question 6: The P31 response to posterior tibial nerve stimulation:
A) Is recorded locally over the lumbar spine
B) Is recordable over a generalized region of scalp
C) Is generated in the peripheral nerve
D) Is a cortical response only
Correct Answer: B) Is recordable over a generalized region of scalp
Rationale: The P31 response to posterior tibial nerve stimulation is a far-field
potential that is recordable over a generalized region of the scalp. It is
generated in the brainstem and is not localized to a specific cortical area.
, Question 7: How many waves of a 60 Hz signal should you see in a 250 mS
sweep?
A) 10
B) 12
C) 15
D) 20
Correct Answer: C) 15
Rationale: At 60 Hz, one complete cycle takes 1/60 = 16.67 ms. In a 250 ms
sweep, the number of cycles is .67 = 15. This calculation is important
for identifying 60 Hz interference in evoked potential recordings.
Question 8: If the bin width of your system is 20 μS, what is the sampling
rate?
A) 5,000 Hz
B) 10,000 Hz
C) 20,000 Hz
D) 50,000 Hz
Correct Answer: D) 50,000 Hz
Rationale: Sampling rate = 1 / bin width = 1 / (20 μS) = 1 / (0.000020 s) =
50,000 Hz. This high sampling rate is necessary to accurately digitize high-
frequency components of evoked potentials without aliasing.
Question 9: Somatosensory evoked potentials are less reliable in patients
with:
