title: The learning curve in post-operative hearing results in vestibular schwannoma surgery.
abstract: OBJECTIVE
  We chronologically investigated whether the hearing preservation (HP) rate improved or not in vestibular schwannoma (VS) surgery.
  
  
  METHODS
  HP surgery has been attempted in 127 VS patients with pre-operative class A and B hearing from 1976 to 1999. The HP rate was chronologically compared with hearing level and tumor size.
  
  
  RESULTS
  The preservation rate of pre-operative class A hearing which was preserved post-operatively as class A has recently been increasing especially in patients with an intracanalicular (IC) tumor. This rate was improved to 67% from 1995, although this was 33% from 1989 to 1994. However, the preservation rate of pre-operative class B in patients with an IC tumor and that of pre-operative class A hearing which was preserved as class A in patients with a larger tumor extending into the posterior fossa, have not improved over the last 10 years.
  
  
  CONCLUSIONS
  These results indicate that the improvement of the HP rate is mainly due to the increased number of patients with an IC tumor with class A pre-operative hearing. In patients with a tumor of 4-20 mm in size, especially in those showing pre-operative class B hearing, there may be histologically some limitations such as gliosis in the cochlear nerve in the preservation rate of good quality (class A or B) of hearing.
authors.affiliation: Department of Otolaryngology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Kanzaki
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
authors.forename: K
authors.initials: K
authors.lastname: Ogawa
mesh_terms: D000293:Adolescent; D000328:Adult; D001300:Audiometry, Evoked Response / Q000379:methods; D001301:Audiometry, Pure-Tone / Q000379:methods; D004428:Ear Neoplasms / Q000150:complications* / Q000601:surgery*; D007758:Ear, Inner / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D006311:Hearing Disorders / Q000175:diagnosis* / Q000209:etiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D009464:Neuroma, Acoustic / Q000150:complications* / Q000175:diagnosis / Q000601:surgery*; D013506:Otologic Surgical Procedures / Q000379:methods; D011182:Postoperative Care; D011300:Preoperative Care; D012720:Severity of Illness Index; D013997:Time Factors; D014057:Tomography, X-Ray Computed