title: Middle ear ventilation status postoperatively after translabyrinthine resection of vestibular schwannoma with mastoid obliteration and Eustachian tube occlusion: is the Eustachian tube enough to ventilate the middle ear without the mastoid air cell system?
abstract: BACKGROUND
  Gas pressure balance is essential for maintaining normal middle ear function. The mucosal surfaces of the middle ear, the mastoid air cell system (MACS), and the Eustachian tube (ET) play a critical role in this process; however, the extent that each of these factors contributes to overall middle ear ventilation is unknown. The objective of this study was to determine if the ET alone can maintain normal middle ear pressure without the MACS. To do this, we reviewed subjects who had their MACS completely removed with translabyrinthine (TL) surgery for vestibular schwannoma.
  
  
  METHODS
  A retrospective chart review was done to collect pre and postoperative tympanometry data from patients who underwent resection of vestibular schwannoma. Data from the operative side was compared to the non-operative side at 2 years post-op.
  
  
  RESULTS
  Twenty-four patients were included in this study. Of these, 63 % achieved a type A tympanogram at 2 years post-op in the TL resection group, implying an ability to maintain middle ear pressure in the absence of a mastoid cavity. Because some had negative pressures post TL resection, the average change in pre and postoperative pressure was -37.5 daPa for the operative side and 7.8 daPa for the non-operative side. This was significantly different.
  
  
  CONCLUSIONS
  The difference for change in pre and postoperative pressure and compliance between operative and non-operative side might be expected from the ET plugging during TL resection. However, more interesting are those patients in whom the ET presumably reopens, and in these subjects, despite having no mastoid compartment at all, and the space obliterated with fat, they were still able to maintain normal ventilation of the middle ear space.
  
  
  CONCLUSIONS
  Our findings imply that the ET alone is adequate to ventilate at least the reduced middle ear space following TL surgery in most subjects, and perhaps in 100 % if the ET hadn't been plugged during surgery. Hence, the mastoid air cell system, even when healthy, is not needed to maintain air in the middle year cleft.
authors: Division of Otolaryngology-Head & Neck Surgery, Department of Surgery, Dalhousie University, Room 3184 Dickson Building, VGH Site, 1278 Tower Road, QEII HSC, Halifax, NS B3H 2Y9, Canada.
authors: James
authors: J
authors: Belyea
authors: Division of Otolaryngology-Head & Neck Surgery, Department of Surgery, Dalhousie University, Room 3184 Dickson Building, VGH Site, 1278 Tower Road, QEII HSC, Halifax, NS B3H 2Y9, Canada.
authors: Brandon
authors: B
authors: Wickens
authors: Division of Otolaryngology-Head & Neck Surgery, Department of Surgery, Dalhousie University, Room 3184 Dickson Building, VGH Site, 1278 Tower Road, QEII HSC, Halifax, NS B3H 2Y9, Canada. m.bance@dal.ca.
authors: Manohar
authors: M
authors: Bance
mesh_terms: D000158:Acoustic Impedance Tests; D000293:Adolescent; D000328:Adult; D000368:Aged; D004432:Ear, Middle / Q000502:physiology / Q000503:physiopathology*; D005064:Eustachian Tube / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008416:Mastoid / Q000502:physiology / Q000503:physiopathology*; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000503:physiopathology / Q000601:surgery*; D011312:Pressure; D012189:Retrospective Studies
keywords: Eustachian tube; Mastoid air cell system; Middle ear ventilation; Pressure regulation; Tympanogram