BAER Flashcards
Know ear anatomy
(slides 1-12)
Know the ascending central auditory pathway
(slides 12-16)
* Receptive organ: organ of corti
* 1° sensory neurons: bipolar cells. Dendrites = synapse with hair cells. Cell bodies =** spiral ganglion** (in bony cochlea). Axons = form cochlear nerve as leaving the cochlea.
* Dorsal and ventral cochlear nuclei (rostral medulla). DCN axons form the acoustic stria and join the contraolateral lateral lemniscus. VCN axons synapse on ipsi + controlateral dorsal nucleus of the trapezoid body.
* Lateral lemniscus (pons) bilaterally
* Caudal colliculis (midbrain): integration and reflex center
* medial geniculate nucleus (thalamus): relay center
* 1° auditory cortex (temporl lobe)
AERs represent the ____ latency components of auditory evoked responses
Early (0-10ms)
3 types of BAER stimuli
- Air-conducted click
- Ton-bip or burst
- Bone-conducted click
Air-conducted clicks are square DC pulses at center frequency of ____ Hz, stimulating the ____ of the cochlea.
2-4 kHz, base (high f)
Tone-pip or burst: what’s it for?
Produces a narrow peak at a selected frequency, to stimulate a specific area of the cochlea. To assess sound sensitivity to various frequencies.
Bone-conducted click: what’s that?
Direct stimulation of the cochlea using a bone-stimulator. By-passes the middle ear. Useful to distinguish sensorineural vs conductive deafness.
What is the masking noise? what does it prevent?
Click delivered to controlateral ear. 20-30 dB lower intensity than stimulated ear. Goal: prevent the cross-over artifact
Describe anatomical placement of the 3 electrodes
- Recording: vertex
- Ground: nuchal crest (electrically neutral)
- Reference: mastoid or dorsal spinous process of T1
slide 25
How to determine the BAER threshold (dB) of a patient?
- Set intensity level to a point where no BAER response is seen
- Increase by 5 dB increments until wave V appears (wave V threshold)
BAER is ____ of arousal level
independant (awake, sedated, GA)
Know the 7 BAER waveform generators
Slide 19
Normal BAER
How is hearing confirmed ?
Presence of 4-5 vertex-positive waves
Normal BAER
How to measure:
a) wave amplitude (uV)?
b) Absolute latencies (ms)?
c) Interpeak latencies (ms)?
a) +ve peak -> following -ve trough
b) stimulus -> +ve peak
c) peak-peak
Normal BAER
Wave I occurs within ____ ms latency
1-2 ms
What should we account for when measuring absolute latencies
0.9 ms delay from tubal insert
Which interpeak latencies are most commonly measured and what do they represent
I-III: dt from cochlear nerve -> pons
I-V: cochlear nerve -> midbrain
Slide 32
What is the central conduction time
Interpeak latency from I-V
Know the effect of mastoid vs T1 reference on waveforms
Slide 35