Evoked Potentials Flashcards
7 cards from real EEG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Evoked Potentials flashcards as text
A unilaterally prolonged P100 latency on visual evoked potential testing is most characteristically associated with which condition?
Answer: Demyelinating optic neuritis (multiple sclerosis)
Demyelinating optic neuritis, most commonly seen in multiple sclerosis, slows conduction along the optic nerve, resulting in a prolonged P100 latency that may persist even after clinical recovery.
In a BAEP recording, absent Wave I with relatively preserved Waves III and V most likely indicates pathology at which level?
Answer: Cochlea or cochlear nerve peripheral to the brainstem
Wave I reflects the distal cochlear nerve action potential; its absence with central waves preserved indicates peripheral auditory dysfunction (cochlea or nerve), not brainstem pathology.
During intraoperative neurophysiological monitoring, a sudden 50% decrease in SSEP amplitude or a 10% increase in latency should prompt what immediate action?
Answer: Alert the surgical team immediately
The '50/10 rule' is the standard alert criterion: a >50% amplitude drop or >10% latency increase warrants immediate notification of the surgeon to allow corrective intervention before permanent injury.
What is the upper limit of normal for the interpeak latency I–V (IPL I–V) in BAEPs recorded from a typical adult?
Answer: Less than 4.4 ms
The IPL I–V, representing total brainstem conduction time, normally does not exceed approximately 4.4 ms; values beyond this suggest central conduction slowing.
Bilateral prolongation of SSEP cortical latencies with normal peripheral nerve and plexus responses most strongly suggests pathology at which level?
Answer: Cervical spinal cord (myelopathy)
Normal peripheral potentials with delayed cortical responses imply a central conduction abnormality; bilateral symmetric involvement points to the cervical cord rather than unilateral brain pathology.
The N20 component of the median nerve SSEP is primarily generated by which brain structure?
Answer: Primary somatosensory cortex (Area 3b, S1)
N20 reflects the initial thalamocortical volley arriving at primary somatosensory cortex (Brodmann area 3b) on the posterior bank of the central sulcus.
Which technical factor most directly degrades SSEP and BAEP signal quality by introducing 60 Hz noise and poor signal-to-noise ratio?
Answer: High electrode impedance
High electrode impedance increases susceptibility to capacitively coupled electrical interference (60 Hz), which obscures the small far-field potentials and cannot be fully corrected by averaging.