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Cochlear nerve injuries caused by cerebellopontine angle manipulations

An electrophysiological and morphological study in dogs

Tetsuji Sekiya and Aage R. Møller

P reservation of hearing is an important consideration in neurosurgical operations such as microvascular decompression of the cranial nerves 7, 8 and resection of acoustic neuromas. 9, 15 It has been known for a long time that the cochlear nerve is vulnerable, and that even delicate operative manipulations can injure the cochlear nerve sufficiently to cause permanent hearing loss. As these operative procedures are being performed more frequently, the need to find ways to decrease hearing damage has become greater. However, the precise mechanisms leading to

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Norihito Shimamura, Tetsuji Sekiya, Akinori Yagihashi, and Shigeharu Suzuki

N eurosurgeons working in the CPA have been empirically recognizing that the cochlear nerve is highly vulnerable to traumatic stress resulting from surgical procedures. 17, 19 Therefore, prevention of trauma-induced hearing loss is an extremely important issue for neurosurgeons who manage lesions in this neuroanatomical area. 17, 19 Despite its importance, no one yet precisely understands how the cochlear nerve degenerates following traumatic stress. In the present study, we quantitatively induced cochlear nerve degeneration by compressing the CPA portion

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Hiromichi Umezu and Tadashi Aiba

preserved if it remained in the serviceable range after surgery. Special attention was focused on the shape and location of the cochlear nerve at the tumor surface, based on the operative record. The cochlear nerve was defined as one of three possible shapes; the classification scheme is modified from that proposed by Koos and Perneczky. 15 In Type 1, the cochlear nerve fibers are dispersed on the tumor surface and cannot be differentiated from the tumor capsule. In Type 2, the nerve fans out but is distinguishable from the tumor capsule ( Fig. 1 left ). In Type 3

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Raymund L. Yong, Brian D. Westerberg, Charles Dong, and Ryojo Akagami

schwannoma, the major determinant of hearing outcome is the length of contact between the cochlear nerve and the vestibular schwannoma, or the degree of cochlear nerve stretch imparted by the tumor, as suggested originally by the AAO-HNS guidelines. The extracanalicular and intracanalicular lengths of contact were investigated as separate variables in an attempt to determine if 2 different relationships were in fact present. Clinical Material and Methods Patients were retrospectively identified by review of surgical records. Those who underwent gross-total resection

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Christian Scheller, Andreas Wienke, Marcos Tatagiba, Alireza Gharabaghi, Kristofer F. Ramina, Oliver Ganslandt, Barbara Bischoff, Cordula Matthies, Thomas Westermaier, Gregor Antoniadis, Maria Teresa Pedro, Veit Rohde, Kajetan von Eckardstein, Thomas Kretschmer, Johannes Zenk, and Christian Strauss

V estibular schwannomas (VSs) account for 6%–8% of all intracranial tumors. Treatment options for VS include microsurgical removal or stereotactic radiosurgery (SRS). 12 The goal of modern VS surgery is total tumor removal with preservation of facial and cochlear nerve function. 11 So far, the stability of hearing preservation and the regeneration potential of the cochlear nerve after VS surgery have been analyzed retrospectively. 2 , 3 , 8 , 12 , 17 Long-term follow-ups after SRS showed serviceable hearing rates in 44 patients with VS at 1, 3, 5, 7

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Tomio Sasaki, Tadahisa Shono, Kimiaki Hashiguchi, Fumiaki Yoshida, and Satoshi O. Suzuki

R ecent advances in microsurgical techniques, instrumentation, and intraoperative monitoring of neuronal functions have shifted the goals in VS surgery. Preservation of cochlear nerve function, as well as anatomical and functional preservation of the facial nerve, is often the goal in patients whose hearing is retained preoperatively. Surgeons must achieve maximal tumor removal and preservation of these nerve functions simultaneously. The authors of several studies have reported the results of surgery for VS resection with respect to the preservation of

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Daniele Starnoni, Giulia Cossu, Rodolfo Maduri, Constantin Tuleasca, Mercy George, Raphael Maire, Mahmoud Messerer, Marc Levivier, Etienne Pralong, and Roy T. Daniel

C ochlear nerve monitoring and preservation during vestibular schwannoma (VS) resection surgery is often challenging, especially for large tumors (extrameatal diameter > 30 mm or grade IV according to the Koos grading scale). 1 , 2 Brainstem auditory evoked potentials (BAEPs) and cochlear compound nerve action potentials (CNAPs) have been shown to be useful intraoperative tools to preserve cochlear nerve function. Their benefits are most significant in cases of small- to medium-sized tumors 3 – 5 and less useful in cases of large tumors. In this setting

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Masanori Yoshino, Taichi Kin, Akihiro Ito, Toki Saito, Daichi Nakagawa, Kenji Ino, Kyousuke Kamada, Harushi Mori, Akira Kunimatsu, Hirofumi Nakatomi, Hiroshi Oyama, and Nobuhito Saito

indicated that DTT was able to predict facial nerve location in relation to VS, descriptions of DTT predicting cochlear nerve location in relation to VS have been lacking. With the aim of addressing these issues, we investigated DTT conditions for VS. As a result, we proposed a more reliable method than previously reported 24 and were able to depict fibers corresponding with the course of the cochlear nerve 23 ; however, the rate of depiction of fibers corresponding to the course of the facial nerve was lower than previously reported. In addition, predicting before

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Nobuyuki Watanabe, Takuya Ishii, Kazuhiko Fujitsu, Shogo Kaku, Teruo Ichikawa, Kosuke Miyahara, Tomu Okada, Shin Tanino, Yasuhiro Uriu, and Yuichi Murayama

H earing preservation has become an increasingly important goal of vestibular schwannoma surgery (VSS) in patients who have useful hearing preoperatively. Several intraoperative neurophysiological methods have been developed for this purpose. 2–5 , 10 , 12 , 17 , 18 We have developed a bipolar forceps–type electrode, called the cochlear nerve compound action potential (CNAP) mobile tracer (MCT), for cochlear nerve mapping. Simultaneous monopolar and bipolar recording is possible with this device. The MCT requires only a short time (no more than 2 seconds) for

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Takuzou Moriyama, Takanori Fukushima, Katsuyuki Asaoka, Pierre-Hugues Roche, David M. Barrs, and John T. McElveen Jr.

tumors. Although the selection of a particular approach is generally dependent on the surgeon's preference, it has been our belief that the selection of the approach should be individualized according to the size or location of the tumor. In this study, we report the results of hearing preservation surgery for acoustic neuroma in a consecutive series of patients in whom the surgical approach was individualized. We also evaluated the importance of adhesion between the cochlear nerve and the tumor. Clinical Material and Methods We reviewed 63 consecutive