Internal Acoustic Canal Reconstruction after Drilling via Retrosigmoid Approach – Step By Step Technique and Tips
Complete exposure of internal auditory canal (IAC) is a fundamental step cerebellum-pontine angle (CPA) surgery such as vestibular schwannoma and petroclival meningiomas. So important as complete exposure is adequate closure to avoid complications such as CSF fistula and meningitis. In most series, rates of leakage ranges between 2.4% to 18.7% with different closure techniques. The aim of this article is to describe a safe technique for closure of IAC using a 3-fold protection after retrosigmoid approach in supine position with contralateral rotation of the head to removal of vestibular schwannoma. Description is performed in a stepwise manner and some tips are reinforced. After cistern drainage and exposure of CPA, a dural flap is performed in the region, which will be drilled (posterior wall of IAC). It is dissected from the bone and placed inferiorly based in a pedicle over the jugular foramen. After removing completely the tumor, palpation of IAM fundus and inspection of with endoscope is needed to ensure that no mastoid cells are opened. If this is noticed, under direct (microscopic or endoscopic) view, a plug of muscle should be place adjusted into this aperture and left with fibrin sealant. So, the dural flap should de placed completely outstretched over the nerves inside IAM, covering all its extension. Fibrin sealant is applied over the dural flap and another piece of muscle should be placed into the IAM, covering the dural flap with fibrin sealant again over it. This 2-fold (or three) protection of IAM is a fundamental step to avoid postoperative CSF paradoxical CSF-leak. This technique was performed in last 500 cases of vestibular schwannoma microsurgical resection with good results in avoiding leakage. To improve results of the technique, an endoscopic inspection is performed to detect open mastoid cells in regions not visible under microscopy. This technique besides reducing CSF leakage protects the nerves in its intrameatal segment since this dural flap functionally simulates the posterior wall of IAC.