Evaluation of Surgical Approaches to Endoscopic Auditory Brainstem Implantation

Abstract

This study finds that endoscopy provides superior visualization of the lateral recess of the fourth ventricle than the operating microscope with all approaches. The retrosigmoid approach is recommended, as it provides the best view of the implantation site and the easiest angle for placement of the prosthesis. The use of the endoscope may allow for a smaller craniotomy than with conventional microscopic techniques, depending on tumor size. The translabyrinthine approach provides a good view of the lateral recess but had no advantage over other approaches. The middle cranial fossa approach is only possible with angled endoscopes; however, it is technically the most difficult and places the facial nerve at greatest risk.

Multidisciplinary approach for ABI recipients: surgical, electrophysiologic, and behavioral outcomes

“…Brackmann et al [7] noted that the dorsal nucleus in lower mammals forms a characteristic bbulgeQ on the brainstem surface, which they have not observed in humans. We have seen this surface bulge in cadaveric specimens as well as in our patients when performing endoscopic placement, which may indicate that such a landmark is, at best, inconsistent and therefore unreliable [5]. Further complicating localization of the dorsal cochlear nucleus is its position within the lateral recess of the fourth ventricle, an area reported to be not directly visible within the standard translabyrinthine surgical field [8].…”

“…as we have described previously. [5] Intraoperative EABR was also performed using the paradigm recommended by Cochlear Americas, with the exception that repeated mapping was completed until optimal placement, as defined by the maximum number of active auditory electrodes achieved. Table 1 and Figs.…”

“…However, the use of the endoscope in placement of an ABI electrode array has been explored to accomplish this goal [5]. In addition, the endoscope has been employed successfully as an adjunct to resection of acoustic neuromas and surgery of the vestibular nerve [6].…”

Minimally Invasive Endoscopic and Endoscopy-Assisted Microsurgery of Vestibular Schwannoma

“…Endoscopy was also evaluated for the placement of an auditory brainstem implant via the translabyrinthine, retrosigmoid, and middle cranial fossa approaches. Authors stated that endoscopy provided superior visualization of the lateral recess of the fourth ventricle than the operating microscope with all approaches and recommended the retrosigmoid approach as it provides the best view of the implantation site and the easiest angle for placement of the neuroprosthesis (Friedland & Wackym, 1999). Endoscopic technique and assistance during microvascular decompression of the facial nerve for hemifacial spasm, trigeminal nerve for trigeminal neuralgia, glossopharyngeal nerve for glossopharyngeal neuralgia, and cochlear nerve for incapacitating tinnitus were shown to add additional accuracy rate in identifying nerve-vessel conflicts and even revealed a significant number of persistent nerve compression in despite negative binocular microscopic evidence (Magnan et al 1993, Magnan et al 1997, Jarrahy et al 2000, Miyazaki et al 2005, Chen et al 2008, Guevarra et al 2008.…”

“…The foramen of Luschka, the sleevelike lateral recess of the fourth ventricle, is situated at the lateral margin of the pontomedullary sulcus, just behind the junction of the glossopharyngeal nerve with the brainstem, and immediately posteroinferior to the junction of the facial and vestibulocochlear nerves with the brainstem. The foramen itself is infrequently well visualized but tuft of the choroid plexus protruding out of the foramen of Luschka over the posterior surface of the glossopharyngeal and vagus nerves, just inferior to the junction of the facial and vestibulocochlear nerves with the brainstem can be well identified (Friedland & Wackym, 1999, Rhoton, 2000a). Flocculus, projects from the margin of the lateral recess and foramen of Luschka into the cerebellopontine angle, just posterior to facial and vestibulocochlear nerves.…”