Comparison of the auditory-evoked brainstem response wave I to distortion-product otoacoustic emissions resulting from changes to inner ear blood flow.
OBJECTIVE
Examine and compare in detail the time courses of the auditory brainstem response (ABR) wave I amplitude and latency to the distortion-product otoacoustic emission (DPOAE) amplitude and phase measured in the rabbit model following deliberate obstruction of cochlear blood flow (CBF).


METHODS
Using a posterior fossa craniotomy in five rabbits, the internal auditory artery (IAA) was compressed with a probe. ABR and otoacoustic emission were continuously monitored before, during, and after the compressions.


RESULTS
ABR wave I amplitudes demonstrated measurable decreases at a mean of 28.3 s after IAA compression, whereas DPOAE amplitudes decreased after a mean of 14.8 s. Wave I latencies began to increase at a mean of 18.3 s after occlusion, while DPOAE phase measures changed after a mean of only 4.8 s following IAA compression. The time-course patterns were similar for the amplitudes of both ABR wave I and DPOAE.


CONCLUSIONS
ABR wave I amplitude follows a similar, though delayed (by approximately 10 s) time-course pattern to that of the DPOAE following IAA compression. The implication of these findings for intraoperative auditory monitoring is that changes in many currently employed measures will lag actual surgically induced alterations in CBF by at least 20 to 30 s.
Telischi
F F
FF
Department of Otolaryngology-Ear Institute, University of Miami, Florida 33101, USA.
Mom
T
T
Agrama
M
M
Stagner
B B
BB
Ozdamar
O
O
Bustillo
A
A
Martin
G K
GK
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001300:Audiometry, Evoked Response / Q000379:methods; D001307:Auditory Perception / Q000502:physiology; D002528:Cerebellar Neoplasms / Q000601:surgery; D002530:Cerebellopontine Angle / Q000601:surgery; D003051:Cochlea / Q000098:blood supply* / Q000502:physiology; D003056:Cochlear Nerve / Q000502:physiology; D004195:Disease Models, Animal; D004424:Ear Canal / Q000601:surgery; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D016343:Monitoring, Intraoperative; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology*; D010865:Pilot Projects; D011817:Rabbits; D013997:Time Factors