Endolymphatic duct violation during retrosigmoid dissection of the internal auditory canal: a human temporal bone radiographic study.
OBJECTIVE
Successful hearing preservation after acoustic neuroma resection is sometimes complicated by delayed hearing deterioration. The goal of this study was to investigate the hypothesis that internal auditory canal (IAC) drilling during retrosigmoid acoustic neuroma removal may result in endolymphatic duct (ELD) injury, a potential cause of delayed hearing loss (HL) after hearing preservation surgery.


METHODS
Temporal bone anatomic and radiographic study and literature review.


METHODS
Twenty-one human temporal bones were analyzed with high-resolution multislice computed tomography (HRMCT) and subjected to standard retrosigmoid IAC dissection with labyrinthine preservation and follow-up HRMCT for analyses of the ELD. A MEDLINE search was performed of studies documenting long-term hearing preservation outcomes after retrosigmoid dissection.


RESULTS
Five of 21 (24%) bones were found to have violation of the ELD despite preservation of labyrinthine structures and the endolymphatic sac. These results correlate with the mean incidence of long-term hearing decline (26.6%). Reviews of human and animal studies indicate that injury to the ELD may create endolymphatic hydrops.


CONCLUSIONS
The ELD is vulnerable to injury during IAC dissection even if labyrinthine structures at the lateral aspect of the IAC are preserved. These findings may be helpful in explaining and potentially preventing some cases of long-term hearing deterioration that may be a result of endolymphatic hydrops after ELD injury during acoustic tumor removal. Careful preoperative review of imaging studies using HRMCT may prove useful before retrosigmoid dissection.
Sulman
Cecille G
CG
Department of Otolaryngology, Head and Neck Surgery, University Hospitals of Cleveland, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
Vecchiotti
Mark A
MA
Semaan
Maroun T
MT
Lewin
Jonathan S
JS
Megerian
Cliff A
CA
D002102:Cadaver; D007758:Ear, Inner / Q000601:surgery*; D004711:Endolymphatic Duct / Q000293:injuries*; D006801:Humans; D007431:Intraoperative Complications / Q000209:etiology*; D009464:Neuroma, Acoustic / Q000601:surgery*; D013701:Temporal Bone / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods