ImportanceOpening the cochlear‒carotid recesses through the endoscope-assisted modified translabyrinthine approach to treat lesions in the petrous apex has been demonstrated to preserve the cochlea and hearing. The objective parameters of recesses and their relationships with vital structures were fundamental to the effective application of this technique.ObjectiveHerein, we present a quantitative analysis of cochlear‒carotid recesses on high-resolution computed tomography (HRCT) images and discuss their implications for hearing preservation in the surgical management of massive petrous bone cholesteatomas (PBCs).DesignObservational study.ParticipantsTwenty samples (40 sides) obtained between April and June 2021 radiographically via HRCT.MethodsHRCT images of 40 ears were acquired at 0.60 mm thickness and processed via Mimics. The intrinsic structures of the temporal bone were reconstructed in a 3D view. The morphological data were precisely measured on multiplanar reconstructed images. In addition, clinical implications were demonstrated in one patient with massive temporal bone cholesteatoma.ResultsA 3D model of the cochlear‒carotid recesses was reconstructed. The recesses were essentially divided into 2 parts, namely, the triangle anterior and superior to the cochlea (TASC) and the triangle anterior and inferior to the cochlea (TAIC). The size of the cochlear‒carotid recesses varied widely among the samples. The TASC was accessible in 80% of the samples via a conventional ear endoscope with a diameter of 3 mm, while the applicability of the TAIC was 62.5%. We further discovered that the low position of the trigeminal nerve impression and the small distance between the cochlea and the jugular bulb suggested narrow recesses. The thickness of the compact bone shell of the cochlear lumen acted as a safe drilling divider.ConclusionsHRCT and 3D reconstruction clearly displayed cochlear‒carotid recesses. For patients with massive PBC, the use of an endoscope to open recesses is feasible in the majority of cases and increases the possibility of preserving the structure and function of the cochlea. Individualized preoperative measurements of cochlear‒carotid recesses via HRCT could help surgeons perform safe and accurate dissection.
Keywords: 3D reconstruction; cochlear-carotid recesses; hearing preserving; petrous bone cholesteatoma.