Exclusive endoscopic transcanal transpromontorial approach: a new perspective for internal auditory canal vestibular schwannoma treatment

Abstract

OBJECTIVE The aim of this study was to describe the first case series in which an exclusive endoscopic transcanal transpromontorial approach (EETTA) was used to treat small vestibular schwannomas (VSs) and meningiomas of the internal auditory canal (IAC). METHODS The authors performed a retrospective review of patients who had undergone surgery using an EETTA to the IAC at 2 university tertiary care referral centers during the period from November 2011 to January 2015. RESULTS Ten patients underwent surgery via an EETTA for the treatment of VS in the IAC at the University Hospital of Modena or the University Hospital of Verona. The patients had Koos Grade I or II tumors and American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) Class D hearing status preoperatively. Gross-total resection was achieved in all patients. No major complications such as cerebrospinal fluid leakage or hemorrhage were reported. In 7 of 10 (70%) patients, facial nerve function was normal immediately after surgery (Rough Grading System [RGS] Grade I). Two patients presented with a transitory facial palsy immediately after surgery (RGS Grade II-III) but experienced complete recovery during the follow-up period. The mean follow-up was 10 months. CONCLUSIONS The EETTA proved to be successful for the removal of VS or meningioma involving the cochlea, fundus, and IAC, with possible lower complication rates and less invasive procedures than those for traditional microscopic approaches. The potential for the extensive and routine use of this approach in lateral and posterior skull base surgery will depend on the development of technology and surgical refinements and on the diffusion of skull base endoscopic skills among the otolaryngological and neurosurgical communities.

Defining the Limits of Endoscopic Access to Internal Auditory Canal

“…The expansion of this technique to IAC and the lateral skull base, however, remains a relatively novel concept with limited published data. The present study supports prior data and suggests that EETA is a viable and safe route of access to the lateral skull base in select cases [5][6][7]9] . The facial nerve was structurally preserved in this study despite the fact that the labyrinthine segment of the facial nerve lies adjacent to the fundostomy created into IAC.…”

“…This distance indicates that caution should be taken when widening the entry point to IAC anteriorly. Our results underscore those of Marchioni et al and others who suggest that visualization of the carotid canal in the protympanum is recommended to maximize safety when using this approach [6][7][8][9]14] .…”

“…Recently, Marchioni et al [9] published the first case series (n=10) of an exclusively endoscopic transcanal resection of Koos Grade I (within IAC) or II (IAC and limited CPA involvement) tumors. All the patients in this cohort had American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) Class D hearing status (from severe to profound hearing loss) preoperatively.…”

“…Recently, Marchioni et al [6][7][8][9] have described an exclusively endoscopic transcanal approach (EETA) to IAC. It differs from traditional approaches as it offers a direct route through the ear canal, a natural orifice of the temporal bone.…”

“…Compared with a posterior or medial approach, EETA does not require any external incisions, soft-tissue dissection, or mastoidectomy. Recent reports have demonstrated that this approach has been used successfully in a limited number of patients [7,9] . Initial data suggest that EETA is applicable to pathologies involving the IAC fundus, petrous apex, pericarotid, and intravestibular areas.…”