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Hypothesis: This study aimed to evaluate whether there is a difference in the degree of intracochlear trauma when the cochlear implant electrode arrays is inserted through different quadrants of the round window membrane., Background: The benefits of residual hearing preservation in cochlear implant recipients have promoted the development of atraumatic surgeries. Minimal trauma during electrode insertion is crucial for residual hearing preservation., Methods: In total, 25 fresh human temporal bones were subjected to mastoidectomy and posterior tympanotomy. The cochlear implant electrode array was inserted through the anterosuperior quadrant of the round window membrane in 50% of the bones and through the anteroinferior quadrant in the remaining 50%. The temporal bones were dehydrated, embedded in epoxy, serially polished, stained, viewed through a stereomicroscope, and photographed with the electrode arrays in situ. The resulting images were analyzed for signs of intracochlear trauma., Results: Histological examinations revealed varying degrees of damage to the intracochlear structures, although the incidence and severity of intracochlear trauma were not influenced by the quadrant of insertion., Conclusions: The incidence and severity of intracochlear trauma were similar in all samples, irrespective of electrode array insertion through the anterosuperior or anteroinferior quadrant of the round window membrane.

Unlabelled: The auditory brainstem implant (ABI) is an option for deaf patients who do not have the whole of their auditory pathways preserved. The surgery, because of its anatomical and functional complexity, requires specific training of the surgeon in an anatomy lab., Aim: To study the surgical anatomy of the surgery for auditory brainstem implant., Study Design: Anatomic study., Material and Method: In this exercise we dissected a fresh cadaver prepared with a dye solution injected into the arteries and intra-cranial veins. The location for the insertion of the electrode for the ABI has been studied through the translabyrinthine access., Results: The surgical technique used for implanting the electrode of the brainstem is similar to that used in the removal of the schwannoma vestibular. The cochlear nucleus complex, composed of the ventral and dorsal cochlear nuclei is the location for placing the electrode. The ventral cochlear nucleus is the principal nucleus for transmission of neural impulses from the VIII par and form the main ascendant route of the cochlear nerve. Neither the ventral nor the dorsal nuclei are visible during surgery and their location depends on the identification of adjacent anatomical structures., Conclusion: The region for the implantation of the electrode in the auditory brainstem implant presents anatomical references that allow its easy identification during surgery.