Hearing preservation after XXXX surgery with intraoperative direct eighth cranial nerve monitoring: Part II. A classification of results.

@entity1 @entity5513 @entity5 @entity865 @entity130
Since the advent of brainstem auditory evoked response audiometry and computerized tomography, small @entity5513 are more frequently found. Often the @entity1 has serviceable hearing, which we would like to preserve during complete @entity5 removal. Since 1978, sixteen @entity1 with @entity5513 have been operated upon through the retrosigmoid suboccipital approach, with the goal of hearing preservation. In 1983, we began using intraoperative direct eighth nerve monitoring, which produced a rapid assessment of cochlear nerve function during the excision of small @entity5513 . The @entity5 varied in size from intracanalicular lesions to one lesion with a 3.0 cm protrusion medial to the porus acousticus. In eight of sixteen cases, intraoperative monitoring was used, and in four of the @entity1 hearing was preserved. In eight cases, intraoperative monitoring was not used, and hearing was preserved in only two @entity1 . The overall success rate--in @entity5 removal with hearing preservation--was 37%. Hearing was preserved in six of eight @entity1 who had @entity5 which measured less than 1.5 cm. In this group of cases, two of the @entity1 had a Class I good hearing result (PTA 0 to 30 dB and 70 to 100% discrimination), one @entity1 had Class III nonserviceable hearing, (PTA 65 to 75 dB and 25 to 45% discrimination), and three @entity1 had Class IV poor hearing, ( @entity865 80 to 100 dB and 0 to 20% discrimination). We found that continuous monitoring of direct eighth-nerve-evoked action potentials were extremely valuable and rapidly indicated reversible cochlear nerve @entity130 .
