Microsurgical Removal Of The Large Acoustic Neuromas By The Retrosigmoid Suboccipital Keyhole Approach

Objective: To evaluate the safety and efficacy of removing large acousticneuromas (＞3.0cm) by the retrosigmoid suboccipital keyhole approach inpark-bench position, and to modify the design of the incision and bone flap.Methods: A retrospective analysis of 37 consecutive cases who suffer fromLarge acoustic neuromas (mean (SD), 4.1 cm) between January 2003 andDecember 2006. All were removed by the retrosigmoid suboccipital keyholeapproach with park-bench position while continuous electrophysiologicalmonitoring provides feedback regarding the exact identity and anatomicaland functional preservation of the facial and cochlear nerves. Design thelocation of the incision and bone flap preoperative which based on the dataof cranial CT and MR, The diameter of bone windows is from 2.5cm to3.5cm. The facial nerve results were graded according to theHouse-Brackmann scale (in 1985), good facial function (grade 1 and grade2), moderate function (grade 3 and grade 4) and poor function (grade 5 andgrade 6),The hearing results were evaluated by use of the classification andthe guidelines of the American Academy of Otolaryngology-Head and NeckSurgery (AAO-HNS), serviceable hearing:pure tone threshold average(PTA)≤50dB, speech discrimination score(SDS)≥50%, Compared withpreoperation,+/-15 dB pure-tone average or +/-15% speech discriminationwas definited as hearing preservedResults: The tumour was removed completely in 15 of 37patients(40.5%).Near-total removed in 18(48.6%), subtotal removed in4(10.8). The facial nerve was anatomically preserved in 35(94.6%)of the patients and 2 cases whose facial nerve couldn't preserved,one whounderwent primary end-to-end nerve anastomosis, another who appliedhemihypoglossal-facial combination six months later, anatomicallypreservation of cochlear nerve was achieved in 16 of37(43.2), Cerebrospinal fluid leak occurred in 3 patients, meningitisoccurred in 3 cases including 2 asepsis meningitis too. No continuouspostoperative headache, the patients who underwent near-total and subtotalremoved have had a gamma knife, all patients have follow-up from 4 to 24months, 81% had excellent facial nerve function (House-Brackmann grade1/2).hearing preservation in 19 patients, all of them have near-total orsubtotal, one patients who no servicable hearing preoperative recoverd toservicable hearing six months later. one had to another operate because ofrecurrence 12 months later.Conclusions: The modified design methods of incision and bone flapdiminishes the unexpected complications according to incision, the locationof bone flap is much fit to the need of operation, which reducesunnecessary craniectomy and exploration of brain tissue, The using of theretrosigmoid suboccipital keyhole approach can minimizes the trauma andcomplication due to operation, and was advantage with beauty, The rate ofthe facial nerve preservation is equivalent with the traditional one. Above all,Itis suitable to the microsurgerical removal of large acoustic neuroma, and theefficacy and safety is equivalent with the traditional one.