Sheep are used as a large-animal model for otology research and can be used to study implantable hearing devices. However, a method for temporal bone extraction in sheep, which enables various experiments, has not been described, and literature on middle ear access is limited. We describe a method for temporal bone extraction and an extended facial recess surgical approach to the middle ear in sheep.
Ten temporal bones from five Hampshire sheep head cadavers were extracted using an oscillating saw. After craniotomy and removal of the brain, a coronal cut was made at the posterior aspect of the orbit followed by a midsagittal cut of the occipital bone and disarticulation of the atlanto-occipital joint. Temporal bones were surgically prepared with an extended facial recess approach. Micro-CT scans of each temporal bone were obtained, and anatomic dimensions were measured.
Temporal bone extraction was successful in 10/10 temporal bones. Extended facial recess approach exposed the malleus, incus, stapes, and round window while preserving the facial nerve, with the following surgical considerations: minimally pneumatized mastoid; tegmen (superior limit of mastoid cavity) is low-lying and sits below temporal artery; chorda tympani sacrificed to optimize middle ear exposure; incus buttress does not obscure view of middle ear. Distance between the superior aspect of external auditory canal and tegmen was 2.7 (SD 0.9) mm.
We identified anatomic landmarks for temporal bone extraction and describe an extended facial recess approach in sheep that exposes the ossicles and round window. This approach is feasible for studying implantable hearing devices.
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We acknowledge Jonathan May of May Family Enterprises Inc. for supplying the sheep specimens. We also acknowledge Christopher B. Damoci, Manager of the Oncology Precision Therapeutics and Imaging Core (OPTIC) at Columbia University Medical Center, for his assistance with the micro-CT scans. The Columbia University Medical Center Cancer Center Support Grant (CCSG), NIH grant #P30 CA013696 (National Cancer Institute) partially funds this shared resource. We also acknowledge Yew Song Cheng, MD, for his comments and suggestions on the paper.
This work was supported by funding from the National Institute on Deafness and Other Communication Disorders (NIDCD) R01 DC016874.
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Below is the link to the electronic supplementary material.
Supplementary file1. Video scrolling through the axial CT scan of presurgical specimen 3R from inferior to superior. (MOV 82236 KB)
Supplementary file2. Video scrolling through the coronal CT scan of presurgical specimen 3R from posterior to anterior. (MOV 92701 KB)
Supplementary file3. Video scrolling through the sagittal CT scan of presurgical specimen 3R from right (lateral) to left (medial). (MOV 105851 KB)
Supplementary file4. Video scrolling through the axial CT scan of postsurgical specimen 3R from inferior to superior. (MOV 75986 KB)
Supplementary file5. Video scrolling through the coronal CT scan of postsurgical specimen 3R from posterior to anterior. (MOV 91274 KB)
Supplementary file6. Video scrolling through the sagittal CT scan of postsurgical specimen 3R from right (lateral) to left (medial). (MOV 67198 KB)
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Waring, N.A., Chern, A., Vilarello, B.J. et al. Sheep as a Large-Animal Model for Otology Research: Temporal Bone Extraction and Transmastoid Facial Recess Surgical Approach. JARO (2023). https://doi.org/10.1007/s10162-023-00907-0