| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1996: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
1)According to the changes in CoBF,CAP and ABR by compression of acoustic neurovascular bundle, we classified these changes into three types of hearing disturbance.
(1)In neural types, Which noticed in 66.7% of cephalad compression cases, prolongation of I-II interpeak latency and decrease of the amplitude of wave II-IV without decrease of CoBF and changes of CAP were noticed as the results of neural conduction blockage.
(2)In cochlear insufficiency type, which noticed in 71.4% of caudal compression cases, allacoustically evoked potential was disappeared folliwed by cochlear ischemia.
(3)In mixed type, as a result of both neural and cochlear ischemia, all acoustically evoked potential was disappeared transiently with partially decreased CoBF.
The results indicate that the cochlear nerve or the internal auditory artery is more susceptible to damage by compression of a cephalad or a caudal compression point, and that the compcepression position is an important determinant in the type of auditory dysfunction and the degree of hearing loss.
2)The following thing became clear from the changes of CoBF and CAP during put and removes of compression on the neurovascular bundle.
(1)Disappear of CAP did not mean the complete shut off of CoBF,it occurred when CoBF decreased 70% or more.
(2)CAP recovered promptly after resuming blood fiow, but only 30% is recovered with more than 30 miniutes complete compression.
(3)When blood flow was left at all, CAP recovered about 60% or more even after 30 minute's compression.
These findings suggested that both the degrees of compromise of CoBF and the duration of ischemia are important factors affecting the recovery of auditory function.
3)Furthermore, after administration of carbogen, the cochlear blood flow was increased and the improvement of CAP was noticed.
We emphasize that carbogen inhalation give the validity toward acute cochlear hearing impairment.
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