Evaluation of round window accessibility to cochlear implant insertion

Leong, A.C.; Jiang, Dan; Agger, Andreas; Fitzgerald-O’Connor, Alec

doi:10.1007/s00405-012-2106-4

Cited by 71 publications

(78 citation statements)

References 14 publications

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“…Total exposure of the RW will allow RW insertion of the cochlear implant electrodes. Leong et al (11) reported that the RW was visible in more than 50% to 89% of adult and 78% of paediatric cases after an optimal posterior tympanotomy. In cases in which the RW niche cannot be totally exposed, one must keep in mind that further dissection of the anatomic boundaries may cause complications such as facial paralysis and taste disorders.…”

Section: Discussionmentioning

confidence: 99%

Revisiting the Anatomy of the Facial Recess: The Boundaries of the Round Window Exposure

et al. 2016

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Background:The exposure of the round window (RW) through the facial recess (FR) is sometimes partial. The anatomic variations that alter RW exposure during cochleostomy have not been clearly defined to date. Aims: The aim of this study was to assess the best FR position in which to achieve the widest exposure of the RW niche and to define the topographic relationship between two other important anatomical structures, the facial nerve (FN) and the chorda tympani (CT). Study Design: Cadaver study. Methods: Twenty-four temporal bones were included in the study. Anterior and posterior epitympanectomy and posterior tympanotomy were performed after mastoidectomy. Bone was removed until the FN and CT were skeletonized and the CT branching point was visible. Two pictures were taken. The first was taken when the facial recess was at its widest exposure, while the second was taken when the RW niche was maximally exposed through the facial recess. Various measurements were taken. Results: The RW niche was totally visible in 19 temporal bones (79.2%). The RW was partially visible in the remaining five bones (20.8%). The unexposed part of the RW lay posteromedial to the FN in these five bones. While the branching point of the CT could be visualized in all cases at the widest exposure of RW, the part of the FN distal to the branching point was hidden in eight subjects (33.3%) under the posterior wall of the external ear canal. Conclusions: The RW niche was totally visible in most of the temporal bones. The RW lay posteromedial to the FN in some cases and total exposure was impossible.

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Section: Discussionmentioning

confidence: 99%

Revisiting the Anatomy of the Facial Recess: The Boundaries of the Round Window Exposure

et al. 2016

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“…RW insertion using the posterior tympanotyomy approach can be more challenging in some cases with limited visibility of the RW. This restricted exposition occurs in 11-22% of children, and conventional bony cochleostomy may then be required [4] . Facial nerve injury is the most concerning complication due to bony overhangs or an abnormal course of the facial nerve [4][5][6] .…”

Section: Discussionmentioning

confidence: 99%

Endoscopic-Assisted Cochlear Implantation: A Case Series

Orhan

Polat²,

Çelik³

et al. 2016

Int Adv Otol

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“…Table 1. St Thomas's classification of round window accessibility with recommended type of surgical approach [5] Figure 1. St. Thomas' Classification of round window accessibility with recommended type of surgical approach [5] Classification of Round Window Accessibility The surgical notes for the 25 patients were retrieved and analysed.…”

Section: Classification Descriptionmentioning

confidence: 99%

“…St Thomas's classification of round window accessibility with recommended type of surgical approach [5] Figure 1. St. Thomas' Classification of round window accessibility with recommended type of surgical approach [5] Classification of Round Window Accessibility The surgical notes for the 25 patients were retrieved and analysed. Amongst the cases where the status of the MPFN was mentioned, there were three where the surgeon specifically stated that he had uncovered the bone overlying the MPFN, and they were also captured on HRCT.…”

Section: Classification Descriptionmentioning

confidence: 99%

“…This enables optimum surgical access to the RWM. The extent of exposure is graded using a classification system developed at St. Thomas' Hospital, which assists in deciding between conventional electrode insertion and RW cochleostomy ( Figure 1 and Table 1) [5] . To date, our success rate with Type I and Type IIa exposure of the RWM is more than 85% of cases.…”

Section: Introductionmentioning

confidence: 99%

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Radiological Dehiscence of the Mastoid Portion of the Facial Nerve after Posterior Tympanotomy: Does It Lead to Increased Risk of Nerve Injury?

Lee¹,

Connor²,

Tysome³

et al. 2014

Int Adv Otol

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OBJECTIVE:We aimed to establish the frequency of postoperative bony dehiscence overlying the mastoid portion of the facial nerve after round window membranous cochleostomy using high-resolution computer tomography, and to ascertain whether this was associated with a higher incidence of facial nerve injury compared with other studies. We also evaluated the usefulness of the St Thomas' classification in predicting the possibility of performing round window insertions. Study Design: Retrospective case series.Setting: Tertiary auditory implant centre. MATERIALS and METHODS:Twenty-five patients who underwent cochlear implantation at our institution, two of whom were operated on bilaterally, yielding 27 ears for analysis. We conducted submillimetric analysis of postoperative high-resolution computer tomography images to ascertain the prevalence of bony dehiscence overlying the mastoid portion of the facial nerve. The type of round window found during surgery was also determined in medical records. RESULTS:We found a radiological dehiscence rate of 40%. None of the patients in our series sustained a facial palsy. We propose some possible reasons for differences between our findings and those of others. All 18 patients with a Type Ia round window, two of the three patients with a Type IIa round window, and none of the four patients with a Type III round window had a successful round window insertion. The classification was found to be a useful predictor of performing round window membranous cochleostomy. CONCLUSION:Thinning of the bony cover of mastoid potion of the facial nerve to the point of radiological dehiscence does not put it at risk. Novice cochlear implant surgeons can therefore be reassured that unroofing the bone overlying the nerve does not pose undue danger.

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Evaluation of round window accessibility to cochlear implant insertion

Cited by 71 publications

References 14 publications

Revisiting the Anatomy of the Facial Recess: The Boundaries of the Round Window Exposure

Revisiting the Anatomy of the Facial Recess: The Boundaries of the Round Window Exposure

Endoscopic-Assisted Cochlear Implantation: A Case Series

Radiological Dehiscence of the Mastoid Portion of the Facial Nerve after Posterior Tympanotomy: Does It Lead to Increased Risk of Nerve Injury?

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