BAER Flashcards
What is the definition of auditory evoked responses? What are the structures implied in different waves? What is their latencies?
Definition: averaged time-locked recording of brain activity in response to externally applied acoustic stimuli.
Waves:
I (1 ms) = cochlear nerve
II (1.8 ms) = cochlear nucleus
III = dorsal nucleus of the trapezoid body
IV = not clearly defined (lateral lemniscus)
V (3.5 ms) = caudal colliculus
VI (4.3 ms) = not clearly defined (medial geniculate nucleus)
VII = not clearly defined (auditory radiations)
Which waves are used for interpeak latencies?
Wave I-III: the approximate time required for the electrical activity generated in the cochlear nerve to reach the pons
Wave I-V: central conduction time - the approximate tirne for this same generated activity to reach the mesencephalon
What is the delay associated with tube insert?
+1 ms delay
(0.9 ms – Strain)
What is the effect of post-natal maturation on BAER?
Latency decreased and amplitude increased
Maximum at 40 days
What are the difference induced by T1 reference?
Increased latency wave I (1.2 msec)
Wave IV usually separated
Decreased amplitudes waves I & II
Wave V is larger
Subpeaks are common
At which age, BAER values are reached in foals? In calves?
Foals: 2-5 days
Calves: birth
What is the function of cochlear microphonics?
Peaks of non-neural peripheral origin: electrical responses that occur in different parts of the cochlea: may arise from the cuticular surface of the hair cells.
Observed just before wave I.
Differentiation of cochlear microphonics from wave I: inverse stimulus polarity.
Condensation or rarefaction since alternating polarity averages the cochlear microphonics.
Absent in congenital sensorineural deafness.
Define BAER cross over effect.
The click stimulus directed at the test ear stimulates the cochlea of the non-test ear detectable wave V from contralateral activation
Partial hearing loss from presbycusis produces what BAER changes?
1. Longer peak latencies
2. Smaller peak amplitudes
3. Elevated hearing thresholds
4. 1 and 2
5. 1,2 and 3
5
What feature of the BAER is most useful for deafness diagnosis in puppies?
1. Peak amplitudes
2. Inter-peak latencies
3. Waveform pattern
4. Peak latencies
5. Hearing threshold
3
Wave V/I amplitude ratio decreases in brainstem disease: true or false?
true
Which one of the following statements about the BAER and deafness is true?
1. Pigment-associated hereditary congenital deafness produces total deafness in an affected ear and can affect one or both ears
2. General anesthesia eliminates the BAER
3. Contralateral white noise is necessary when performing BAER testing
4. The BAER can quantify partial hearing loss, such as with presbycusis
5. Disk electrodes are preferred to subdermal needle electrodes for recording the BAER
1
In pigment-associated congenital deafness, the initial pathology leading to deafness is:
Stria vascularis degeneration
Which one of the following can significantly affect BAER recordings?
1. 1. Head size
2. Stimulus polarity (rarefaction/condensation)
3. Attention state (awake/sleep)
4. Hypothermia
5. Sex
- hypothermia
Why use signal averaging in BAER?
Because unwanted signals (EEG, ECG, …) occur randomly, while desired signal is time locked with respect to the stimulus, the unwanted signals eventually average toward a value of 0, whereas the desired signal averages toward its actual value.
The most common cause of deafness in dogs is:
Congenital hereditary sensorineural
