EDT Evoked Potentials 2 — Questions and Answers
Question 1: Which wave in brainstem auditory evoked potentials (BAEPs) is thought to originate near the inferior colliculus and lateral lemniscus?
- Wave V (Correct answer)
- Wave I
- Wave II
- Wave III
Correct answer: Wave V
Wave V is the largest and most reliable BAEP component and is generated in the region of the lateral lemniscus and inferior colliculus in the midbrain.
Question 2: What is the approximate normal I-V interpeak latency in brainstem auditory evoked potentials?
- 4.0 ms (Correct answer)
- 1.5 ms
- 8.0 ms
- 10.0 ms
Correct answer: 4.0 ms
The I-V interpeak latency normally measures approximately 4.0 ms and reflects total conduction time through the brainstem auditory pathway from the cochlear nerve to the midbrain.
Question 3: Prolonged P100 latency with preserved amplitude in VEPs is most characteristic of which pathological process?
- Demyelinating disease such as multiple sclerosis affecting the optic nerve (Correct answer)
- Complete optic nerve transection
- Retinal photoreceptor disease
- Glaucomatous optic neuropathy
Correct answer: Demyelinating disease such as multiple sclerosis affecting the optic nerve
Demyelination slows axonal conduction velocity, delaying the P100 latency while the amplitude may remain normal because axons are structurally intact.
Question 4: The popliteal fossa potential in tibial nerve SSEP recordings serves which primary purpose?
- Confirming peripheral nerve activation proximal to the stimulation site (Correct answer)
- Identifying the thalamic relay response
- Verifying correct cortical electrode placement
- Measuring central conduction time
Correct answer: Confirming peripheral nerve activation proximal to the stimulation site
The popliteal fossa electrode records the tibial nerve action potential as it passes behind the knee, confirming the peripheral pathway is intact before the spinal cord segment.
Question 5: Which click stimulus polarity is most commonly used clinically for BAEPs to minimize stimulus artifact?
- Alternating polarity (Correct answer)
- Rarefaction polarity only
- Condensation polarity only
- Silence baseline with no polarity
Correct answer: Alternating polarity
Alternating polarity cancels the cochlear microphonic and reduces stimulus artifact by averaging responses to opposite-polarity clicks, preserving the neural response.
Question 6: The N13 component recorded over the posterior cervical spine in upper extremity SSEPs is generated at which anatomical level?
- Cervical spinal cord and dorsal column nuclei at the cervicomedullary junction (Correct answer)
- Primary somatosensory cortex
- Thalamus
- Brachial plexus
Correct answer: Cervical spinal cord and dorsal column nuclei at the cervicomedullary junction
N13 reflects postsynaptic activity in the cervical dorsal horn and dorsal column nuclei, and is used to differentiate cervical cord lesions from more rostral pathology.
Question 7: What click repetition rate is typically recommended for clinical BAEP recordings to balance efficiency with response quality?
- 10–11 clicks per second (Correct answer)
- 1 click per second
- 50 clicks per second
- 100 clicks per second
Correct answer: 10–11 clicks per second
A rate of approximately 10–11/s efficiently collects data while avoiding the significant amplitude reduction and latency prolongation seen at higher stimulation rates.
EDT Evoked Potentials 2
Which wave in brainstem auditory evoked potentials (BAEPs) is thought to originate near the inferior colliculus and lateral lemniscus?