CNIM Brainstem Auditory Evoked Potentials (BAEP) 2 — Questions and Answers
Question 1: Compared to SSEPs, BAEPs are generally considered more resistant to the effects of anesthetic agents because:
- BAEPs are generated by muscle activity
- The auditory brainstem pathway is subcortical and less sensitive to anesthetic suppression (Correct answer)
- BAEPs use louder stimuli
- Anesthetics selectively suppress cortical responses
Correct answer: The auditory brainstem pathway is subcortical and less sensitive to anesthetic suppression
BAEPs reflect subcortical brainstem activity which is relatively resistant to anesthetic suppression, unlike cortical responses that are highly sensitive to anesthetic agents.
Question 2: Complete loss of all BAEP waves during posterior fossa surgery most likely indicates:
- Equipment calibration error only
- Severe brainstem compression or ischemia requiring immediate surgical attention (Correct answer)
- Normal intraoperative variability
- Patient is too deeply anesthetized
Correct answer: Severe brainstem compression or ischemia requiring immediate surgical attention
Complete loss of all BAEP waves is a critical alarm indicating severe auditory pathway compromise, brainstem ischemia, or significant compression requiring immediate surgical intervention.
Question 3: The I-V interpeak latency in BAEP monitoring reflects conduction through which neural segment?
- Cochlea to cochlear nerve
- Cochlear nerve to inferior colliculus (central auditory brainstem pathway) (Correct answer)
- Inferior colliculus to auditory cortex
- Peripheral ear canal to cochlea
Correct answer: Cochlear nerve to inferior colliculus (central auditory brainstem pathway)
The I-V interpeak latency reflects central auditory conduction time from the cochlear nerve through the entire brainstem auditory pathway to the inferior colliculus.
Question 4: During posterior fossa surgery, an isolated loss of Wave I with preserved Wave V most likely indicates:
- Cochlear or distal nerve VIII injury (Correct answer)
- Central brainstem injury
- Equipment electrode failure at the scalp
- Patient movement artifact
Correct answer: Cochlear or distal nerve VIII injury
Isolated Wave I loss with preserved Wave V suggests peripheral cochlear or distal cranial nerve VIII injury rather than central brainstem involvement.
Question 5: What is the typical stimulus repetition rate used for intraoperative BAEP recording?
- 1–5 Hz
- 10–20 Hz (Correct answer)
- 50–100 Hz
- 200–500 Hz
Correct answer: 10–20 Hz
BAEP stimuli are typically delivered at 10–20 Hz, balancing the need for rapid averaging with avoiding response habituation or overlapping echoes.
Question 6: Surgical retraction of the cerebellum during posterior fossa surgery can cause BAEP changes primarily by affecting:
- The cochlea directly
- Blood supply to the brainstem via compression of the anterior inferior cerebellar artery (AICA) (Correct answer)
- The auditory cortex
- The contralateral auditory pathway
Correct answer: Blood supply to the brainstem via compression of the anterior inferior cerebellar artery (AICA)
Cerebellar retraction can compress or stretch the AICA, compromising blood flow to the cochlea, auditory nerve, and caudal brainstem, causing ischemic BAEP changes.
CNIM Brainstem Auditory Evoked Potentials (BAEP) 2
Compared to SSEPs, BAEPs are generally considered more resistant to the effects of anesthetic agents because: