CNIM Practice Exam Questions
with Verified Answers & Rationales
2026
Question 1: A "far-field" potential is best described as:
A) A potential recorded close to its generator
B) A potential recorded from a distant generator
C) A potential generated by muscle activity
D) A potential that is always negative in polarity
Correct Answer: B) A potential recorded from a distant generator
Rationale: Far-field potentials are recorded from electrodes placed at a
distance from the neural generator. They represent activity from deep or
distant structures such as the brainstem or thalamus. The P14 of the median
nerve SSEP is a classic example of a far-field potential generated in the
medial lemniscus and recorded from scalp electrodes.
Question 2: The central conduction time (CCT) for the median nerve SSEP
is calculated as:
A) N20 latency minus N9 latency
B) N20 latency minus P14 latency
C) P14 latency minus N13 latency
D) N20 latency minus N13 latency
Correct Answer: B) N20 latency minus P14 latency
,Rationale: Central conduction time (CCT) represents the time required for the
neural impulse to travel from the brainstem (P14) to the primary
somatosensory cortex (N20). Prolongation of CCT may indicate dysfunction in
the central somatosensory pathways. The normal CCT for median nerve SSEP
is approximately 5-7 ms.
Question 3: A "stationary potential" in SSEP recording is one that:
A) Changes latency with stimulus intensity
B) Remains at a fixed latency regardless of recording electrode position
C) Is generated by a moving dipole
D) Is always positive in polarity
*Correct Answer: B) Remains at a fixed latency regardless of recording
electrode position
Rationale: Stationary potentials are generated by fixed neural generators
(such as synapses or fiber tracts crossing anatomical boundaries). The N13
potential of the median nerve SSEP is a stationary potential generated in the
dorsal horn of the cervical spinal cord. Stationary potentials are useful for
monitoring because their latency remains stable, making them reliable
indicators of spinal cord function.
Question 4: The N20-P25 complex of the median nerve SSEP is recorded
from:
A) The ipsilateral parietal scalp
B) The contralateral parietal scalp (CP3/CP4)
C) The midline (Cz)
D) The cervical spine (C5)
,Correct Answer: B) The contralateral parietal scalp (CP3/CP4)
Rationale: The N20-P25 complex is recorded from the contralateral parietal
scalp (CP3 for right-sided stimulation, CP4 for left-sided stimulation)
referenced to Fz or a non-cephalic reference. The N20 is the first cortical
response from the primary somatosensory cortex (area 3b).
Question 5: Which of the following is the primary purpose of
somatosensory evoked potentials (SSEPs) during surgery?
A) To monitor motor pathway integrity
B) To monitor the integrity of the somatosensory pathways
C) To monitor cranial nerve function
D) To monitor cortical excitability
Correct Answer: B) To monitor the integrity of the somatosensory
pathways
Rationale: SSEPs are used to monitor the integrity of the somatosensory
pathways, including the peripheral nerves, spinal cord dorsal columns,
brainstem, and somatosensory cortex. Changes in SSEP amplitude or latency
can indicate injury to these pathways during surgery.
Question 6: The P37 peak of the posterior tibial nerve SSEP is generated in:
A) The lumbar spinal cord
B) The brainstem
C) The primary somatosensory cortex (medial aspect)
D) The thalamus
Correct Answer: C) The primary somatosensory cortex (medial aspect)
, Rationale: The P37 peak of the posterior tibial nerve SSEP is the first cortical
response from the primary somatosensory cortex (medial aspect of area 1). It
is recorded from the midline (Cz) referenced to Fz. The P37 occurs
approximately 37 ms after stimulation and is used to assess the integrity of
the somatosensory pathways from the lower extremity.
Question 7: The N9 peak of the median nerve SSEP is recorded from:
A) The contralateral parietal scalp
B) Erb's point (supraclavicular fossa)
C) The cervical spine
D) The midline (Cz)
Correct Answer: B) Erb's point (supraclavicular fossa)
Rationale: The N9 peak is recorded from Erb's point in the supraclavicular
fossa and represents the brachial plexus response. It is used as a peripheral
control to verify that stimulation is reaching the peripheral nerve. The N9 is
the first peak in the median nerve SSEP and occurs approximately 9 ms after
stimulation.
Question 8: SSEPs recordings typically require a bandpass filter setting of:
A) 1-100 Hz
B) 10-1,000 Hz
C) 30-3,000 Hz
D) 100-10,000 Hz
Correct Answer: C) 30-3,000 Hz
Rationale: SSEP recordings typically use a bandpass of 30-3,000 Hz. The low-
frequency filter (30 Hz) removes slow baseline drift and movement artifact,
with Verified Answers & Rationales
2026
Question 1: A "far-field" potential is best described as:
A) A potential recorded close to its generator
B) A potential recorded from a distant generator
C) A potential generated by muscle activity
D) A potential that is always negative in polarity
Correct Answer: B) A potential recorded from a distant generator
Rationale: Far-field potentials are recorded from electrodes placed at a
distance from the neural generator. They represent activity from deep or
distant structures such as the brainstem or thalamus. The P14 of the median
nerve SSEP is a classic example of a far-field potential generated in the
medial lemniscus and recorded from scalp electrodes.
Question 2: The central conduction time (CCT) for the median nerve SSEP
is calculated as:
A) N20 latency minus N9 latency
B) N20 latency minus P14 latency
C) P14 latency minus N13 latency
D) N20 latency minus N13 latency
Correct Answer: B) N20 latency minus P14 latency
,Rationale: Central conduction time (CCT) represents the time required for the
neural impulse to travel from the brainstem (P14) to the primary
somatosensory cortex (N20). Prolongation of CCT may indicate dysfunction in
the central somatosensory pathways. The normal CCT for median nerve SSEP
is approximately 5-7 ms.
Question 3: A "stationary potential" in SSEP recording is one that:
A) Changes latency with stimulus intensity
B) Remains at a fixed latency regardless of recording electrode position
C) Is generated by a moving dipole
D) Is always positive in polarity
*Correct Answer: B) Remains at a fixed latency regardless of recording
electrode position
Rationale: Stationary potentials are generated by fixed neural generators
(such as synapses or fiber tracts crossing anatomical boundaries). The N13
potential of the median nerve SSEP is a stationary potential generated in the
dorsal horn of the cervical spinal cord. Stationary potentials are useful for
monitoring because their latency remains stable, making them reliable
indicators of spinal cord function.
Question 4: The N20-P25 complex of the median nerve SSEP is recorded
from:
A) The ipsilateral parietal scalp
B) The contralateral parietal scalp (CP3/CP4)
C) The midline (Cz)
D) The cervical spine (C5)
,Correct Answer: B) The contralateral parietal scalp (CP3/CP4)
Rationale: The N20-P25 complex is recorded from the contralateral parietal
scalp (CP3 for right-sided stimulation, CP4 for left-sided stimulation)
referenced to Fz or a non-cephalic reference. The N20 is the first cortical
response from the primary somatosensory cortex (area 3b).
Question 5: Which of the following is the primary purpose of
somatosensory evoked potentials (SSEPs) during surgery?
A) To monitor motor pathway integrity
B) To monitor the integrity of the somatosensory pathways
C) To monitor cranial nerve function
D) To monitor cortical excitability
Correct Answer: B) To monitor the integrity of the somatosensory
pathways
Rationale: SSEPs are used to monitor the integrity of the somatosensory
pathways, including the peripheral nerves, spinal cord dorsal columns,
brainstem, and somatosensory cortex. Changes in SSEP amplitude or latency
can indicate injury to these pathways during surgery.
Question 6: The P37 peak of the posterior tibial nerve SSEP is generated in:
A) The lumbar spinal cord
B) The brainstem
C) The primary somatosensory cortex (medial aspect)
D) The thalamus
Correct Answer: C) The primary somatosensory cortex (medial aspect)
, Rationale: The P37 peak of the posterior tibial nerve SSEP is the first cortical
response from the primary somatosensory cortex (medial aspect of area 1). It
is recorded from the midline (Cz) referenced to Fz. The P37 occurs
approximately 37 ms after stimulation and is used to assess the integrity of
the somatosensory pathways from the lower extremity.
Question 7: The N9 peak of the median nerve SSEP is recorded from:
A) The contralateral parietal scalp
B) Erb's point (supraclavicular fossa)
C) The cervical spine
D) The midline (Cz)
Correct Answer: B) Erb's point (supraclavicular fossa)
Rationale: The N9 peak is recorded from Erb's point in the supraclavicular
fossa and represents the brachial plexus response. It is used as a peripheral
control to verify that stimulation is reaching the peripheral nerve. The N9 is
the first peak in the median nerve SSEP and occurs approximately 9 ms after
stimulation.
Question 8: SSEPs recordings typically require a bandpass filter setting of:
A) 1-100 Hz
B) 10-1,000 Hz
C) 30-3,000 Hz
D) 100-10,000 Hz
Correct Answer: C) 30-3,000 Hz
Rationale: SSEP recordings typically use a bandpass of 30-3,000 Hz. The low-
frequency filter (30 Hz) removes slow baseline drift and movement artifact,
