Open Cerebellopontine Angle Pool Of Brainstem Auditory Evoked Potentials

Objective To study the effects of the patefaction ofcerebellopontine angle cistem on brain stem auditory evoked potential.Methods 100 cases with hemifacial spasm(HFS)from Sep, 2007 to Jun,2008 as experimental group(group A),including 44 males , 56females ,with the age between 30 and 68, normal audition,record thediversifies of the V waves'incubation periods before and after thepatefaction of CPA;20 preoperative cases with HFS from Sep, 2007 toJun, 2008 as control group (group B), including 8 males, 12females ,withthe age between 34 and 65,other conditions are similar to group A.Record the numerus of V waves'incubation periods as normal contrast.Results After the patefaction of CPA, the mean extension of V waves'incubation periods is 0.85 ms,at the ratio of 12.9%;after blockage of CPA,the mean reversion is 0.64 ms,at the ratio of 9.8%; and PA:AP is 3.1%,with the mean extension of 0.21 ms. 3 days after operation ,there are 5cases tinnitus, 3cases vertigo and no case with auditory descent .After 3months ,there are no case tinnitus, no case vertigo and no case withauditory descent. Conclusion The extension of V waves'incubationperiods exceed 1 ms without reversion after blockage of CPA indicates the reversible injury of the auditory nerve, so it may signify the injury ofthe auditory nerve at some degree.