- Email: [email protected]
Rare Lesions of the Internal Auditory Canal
Accepted Manuscript Rare Lesions of the Internal Auditory Canal Kentaro Watanabe, M.D., Mary In-Ping Huang Cobb, M.D., Ali R. Zomorodi, M.D., Calhoun D. Cunningham, 3rd, M.D., Yoichi Nonaka, M.D., PhD., Shunsuke Satoh, M.D., Allan H. Friedman, M.D., Takanori Fukushima, M.D., D.M.Sc. PII:
S1878-8750(16)31315-8
DOI:
10.1016/j.wneu.2016.12.003
Reference:
WNEU 4964
To appear in:
World Neurosurgery
Received Date: 26 August 2016 Revised Date:
1 December 2016
Accepted Date: 2 December 2016
Please cite this article as: Watanabe K, Huang Cobb MI-P, Zomorodi AR, Cunningham 3rd CD, Nonaka Y, Satoh S, Friedman AH, Fukushima T, Rare Lesions of the Internal Auditory Canal, World Neurosurgery (2017), doi: 10.1016/j.wneu.2016.12.003. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Watanabe TITLE PAGE
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Title: Rare Lesions of the Internal Auditory Canal
Authors: Kentaro Watanabe, M.D.1, 4, Mary In-Ping Huang Cobb, M.D.1, Ali R. Zomorodi
M.D.1, Calhoun D. Cunningham 3rd M.D.2, Yoichi Nonaka, M.D., PhD.1, 3, Shunsuke Satoh
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M.D.1, 5, Allan H. Friedman,M.D.1, Takanori Fukushima, M.D., D.M.Sc.1,
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Affiliations:
Department of Neurosurgery, Duke University Medical Center, 2301 Erwin Rd, Durham, NC,
27710, USA 2
Department of Surgery, Division of Head and Neck Surgery & Communication Sciences, Duke
Raleigh, NC 27609, USA 3
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University Medical Center, Duke Otolaryngology of Raleigh 3480 Wake Forest Road, Suite 404,
Department of Neurosurgery, Fukushima Takanori Skull Base Center, Shinyurigaoka General
Department of Neurosurgery, Hôpital Lariboisirère, Paris VII-Diderot University 2 rue
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Hospital, 255 Furusawa Aso-ku, Kawasaki, Kanagawa, 215-0026, Japan
Ambroise Pare, Paris, 75475 France 5
Department of Neurosurgery, Southern TOHOKU General Hospital, 7-115 Yatsuyamada,
Koriyama, Fukushima, 963-8052 Japan
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ACCEPTED MANUSCRIPT Watanabe Corresponding Author: Takanori FUKUSHIMA, M.D. DUMC Box 3807
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Durham, NC 27710 Phone: 919.239.0264 Fax: 919.239.0266
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Email: [email protected]
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Key words: internal auditory canal, acoustic neuroma, facial schwannoma, cochlear schwannoma, intermedius schwannoma, meningioma, cavernous hemangioma, MALT lymphoma, arachnoid cyst, lipochoristoma
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Abbreviations:
IAC: Internal auditory canal, RS: Retrosigmoid, MF: Middle fossa, TL: Translabyrinthine, MALT: Mucosa associated lymphoid tissue, MRI: Magnetic resonance imaging, CT: Computed
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tomography, VS: Vestibular schwannoma, CPA: Cerebellopontine angle, ENG: Electoronystagmography, ABR: Auditory brainstem response, PTA: Pure tone average, T1WI:
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T1 weighted image, T2WI: T2 weighted image, GdT1W: T1 with gadolinium contrast, CISS: Constructive interference in steady state, CSF: cerebrospinal fluid
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ACCEPTED MANUSCRIPT Watanabe ABSTRACT
Background: Approximately 95% of tumors occurring within the internal auditory canal (IAC)
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are vestibular schwannomas (VSs). Many undergo stereotactic radiation without definitive tissue diagnosis. Rare IAC tumors are not all radiosensitive and are poorly described. Methods: Between 1992 and 2015, 289 consecutive patients with IAC lesions operated on were
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retrospectively reviewed. Results: Fifteen patients (5.2%) (16 operations) had unusual
histological findings, including non-vestibular schwannomas (two facial schwannomas, two
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cochlear schwannomas, two intermedius schwannomas), three meningiomas, three cavernous hemangiomas, a mucosa associated lymphoid tissue (MALT) lymphoma, an arachnoid cyst, and a lipochoristoma. None of these rare tumors could be identified prior to surgery. Three operative approaches were used: retrosigmoid approach, middle fossa subtemporal approach, or
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translabyrinthine approach. Few complications occurred including facial nerve palsy, loss of hearing, and vestibular function. Five-year average follow up revealed one patient with recurrence. Conclusions: Clinical exam and imaging alone were insufficient to correctly identify
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treatment.
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these tumors. Definitive pathological diagnosis should be strongly considered to help tailor
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ACCEPTED MANUSCRIPT Watanabe INTRODUCTION
Approximately 10% of intracranial tumors occur in the internal auditory canal (IAC) and
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cerebellopontine angle (CPA). The vast majority (95%) of these tumors are vestibular
schwannomas (VSs). VSs originate from myelin-producing schwann cells of the vestibular
portion of the vestibulocochlear nerve [1]. Their overall incidence is rising, reaching 20 per
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million [2], with reasons investigated ranging from increased cell phone use, to improvements and overuse of diagnostic MRI studies [3-6]. Its benign natural history, with no growth or slow
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growth at 1-2 mm per year [7, 8] also contributes to its rising prevalence, estimated at 200 per million [9].
Not all tumors in the IAC and CPA are vestibular schwannomas. In the CPA, meningiomas and
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epidermoids are the next two most common tumors [10]. In the IAC, rare tumors that mimic VSs have been described in 4.3% of a 351-patient consecutive case series [11] and several other case studies. They include hybrid peripheral nerve sheath tumors [12], meningiomas [14-16],
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glioblastoma multiforme [17], metastases [18-20], primary adenocarcinoma [21], arachnoid cysts [22], lipomas [23, 24], lipochoristoma [25-27], melanoma [28, 29], and cavernous hemangiomas
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[10, 30].
With advances in neuroimaging technology, an increasing number of asymptomatic smaller tumors localized to the IAC are being detected. When small and medium sized tumors grow and become more symptomatic, they are often treated with radiosurgery or fractionated radiotherapy without histologic confirmation. However, if progressive enough to require microsurgery,
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ACCEPTED MANUSCRIPT Watanabe operating on radiated tissue is more challenging with almost certain risk of total hearing loss and increased risk of facial nerve paresis. Unusual lesions can be encountered in the IAC, which may not be radiosensitive. We describe here 15 rare IAC tumors that were surgically resected by the
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senior author (TF).
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MATERIALS AND METHODS
We searched retrospectively the clinical database from 1992 to 2015 for patients who underwent
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surgical management of IAC tumors (minimal to no extension into the CPA) by the principal investigator (TF) at four institutions (Duke University Medical Center, Durham, NC; WakeMed Hospital, Raleigh, NC; Southern Tohoku General Hospital, Fukushima, Japan; and Shin Komonji Hospital, Fukuoka, Japan). Surgeries were performed at Duke University Medical
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Center (Durham, NC), Southern Tohoku General Hospital (Fukushima, Japan), Moriyama Memorial Hospital (Tokyo, Japan), Shinyurigaoka General Hospital (Kanagawa, Japan), and Shinkomonji Hospital (Fukuoka, Japan). Approval was
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obtained from the Duke University Institutional Review Board along with a data
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transfer agreement from the four hospitals in Japan. Clinical charts were reviewed and data collected included demographics, clinical symptoms, MRI reports, pre-operative working diagnosis, pathologic diagnosis and descriptions, operative approach, and postoperative complications. Facial nerve palsy was classified using the House Brackman (HB) Scale. The retrosigmoid (RS) approach was used for resection of small to medium sized, proximally located tumors, with the goal of minimum exposure and hearing preservation. Subtemporal middle fossa (MF) approach was used for laterally located tumors filling the fundus, because it provided
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ACCEPTED MANUSCRIPT Watanabe optimal surgical exposure and angulation for tumor resection. The translabyrinthine (TL) approach was used to improve exposure for laterally placed tumors within the IAC, while sacrificing residual, non-serviceable hearing. Summative statistics were performed using MS
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Excel. Based on the small number of rare tumors, no further statistical analysis was performed.
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RESULTS
From 1992 to 2015, 289 consecutive patients who underwent surgical management of an IAC
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lesion by the senior author (TF) were retrospectively reviewed. Based on pathologic reports and operative notes, the majority of these patients had VSs (95%, 274/289). However, 15 of these patients (5.1%) had rare tumors. There were 8 males and 7 females with a mean age of 49.3±12 (Table 1). A total of 16 operations were performed on these 15 patients (one patient had an
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ipsilateral recurrence). Three different surgical approaches were taken, including RS (n = 11), MF (n = 3), and TL (n = 2). None of the patients received radiotherapy (Table 1). The follow up
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range is 1 to 13 years.
Clinical presentation
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Sensorineural hearing loss was the most common presenting symptom (n = 11), followed by tinnitus (n = 6), vertigo (n = 5), and dizziness (n = 4) (Table 1). One patient had baseline facial nerve palsy H & B Grade IV. (Table 1)
Facial Nerve First talk about the 3 patients where facial function was not preserved. In the 6 cases with new
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ACCEPTED MANUSCRIPT Watanabe postoperative facial nerve palsies, severity as measured by the HB scale improved to at least a grade III or lower by one year follow up. Two of these patients underwent a TL approach. The
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remaining four underwent a RS approach.
Two patients with adherent tumors underwent intraoperative resection of the facial nerve, followed by facial reanimation with a sural nerve graft. One of them had a facial nerve
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schwannoma. She developed a facial nerve palsy HB VI that recovered to III at one year followup (Patient #2). The other patient had a cavernous hemangioma with preoperative facial palsy
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HB grade IV that worsened to a grade VI postoperatively. He but recovered with nerve graft to a grade III with nerve graft at one year follow up (Patient #12).
The third case involved a nervus intermedius schwannoma with anatomic preservation of the facial nerve, but postoperatively developed a facial nerve palsy HBV that resolved to II at one
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year follow up (Patient #6).
The fourth case had an intracanalicular meningioma with anatomical preservation of the facial nerve, however postoperativly developed facial nerve palsy HB III that resolved to I at one year
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follow up. (Patient#8)
The fifth case involved a recurrent cavernous hemangioma operated via TL with facial response
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on the tumor on intraoperative neuromonitoring. However he developed a postoperative facial nerve palsy HB IV that recovered to HB II at 6 months follow-up (Patients#10). The last patient had a lipochoristoma with facial nerve response on intraoperative neuromonitoring. However, he developed a postoperative facial nerve palsy HB II that resolved to HB I at 4 months follow-up (Patient #15). Fortunately,the case of the small facial nerve schwannoma (Patient#1) did not have facial palsy
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ACCEPTED MANUSCRIPT Watanabe postoperativly because of the tumor and attachment of the tumor is small.
Vestibular Nerve
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The vestibular nerve was intentionally sacrificed in six cases. Two patients underwent a TL approach, and four underwent RS for tumors of the nervus intermedius, cochlear schwannoma, facial schwannoma, and cavernous hemangioma. All six patients demonstrated gradual
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improvement in balance function with no patient exhibiting disabling dizziness or balance
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problems.
Cochlear Nerve
In the majority of patients (11/16, 68.7 %), hearing function improved (n = 1), remained intact (n = 3), or stably diminished (n = 7). The cochlear nerve was intentionally sacrificed in two patients
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undergoing TL approach and one patient with a cochlear schwannoma. The remaining patients undergoing a MF (n = 2) and RS approach (n =2) had baseline hearing loss that worsened after
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surgery.
Imaging and histopathology
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Two-thirds of the cases (11/16, 68.6%) were assumed to be VS preoperatively (Table 2). Based on clinical symptoms and imaging, we were unable to predict the diagnosis of any patient for the initial operation. Final pathologic diagnoses of rare IAC tumors included 6 schwannomas originating from non-vestibular sources (2 facial schwannomas (Figure 1), 2 cochlear schwannomas (Figure 2), 2 intermedius schwannomas (Figure 3)), three meningiomas, three cavernous hemangioma (Figure 4), a mucosa associated lymphoid tissue lymphoma (MALT)
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ACCEPTED MANUSCRIPT Watanabe (Figure 5), an arachnoid cyst (Figure 6) and a lipochoristoma (Figure 7) (Table 2).
Recurrence
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At a range of 1 to 13 year follow up, 14/15 patients had no recurrence (Table 1). Patient #10 had a recurrence at 5 years with re-resection followed by a stable thin area of enhancement in the
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IAC fundus at 7 year follow up.
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DISCUSSION
We describe here several rare tumors in the IAC. All types of tumors found in this study have been described in at least one other case study. Our rare tumor rate of 5.2% in 289 patients is comparable to the other large case series of 4.3% in 351 patients [12]. Given the limitations of
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two small case series, it is still interesting to note that the majority of our non-VS IAC cases were schwannomas from other origins (n = 6, 43%) compared to only one facial schwannoma in
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theirs. The majority of their non-VS cases were lipomas (n = 6, 40%) and we found none.
Postoperative Cranial Nerve Function
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Overall, patients in our case series had good preservation or improvement of baseline facial nerve, vestibular nerve, and cochlear nerve function. When excluding patients with strategies that were intended to sacrifice facial nerve function (e.g., intentional facial sacrifice with reanimation, or cases where the facial nerve was severely involved with the tumor), facial nerve function was noted to be normal or near normal in 86.7% of patients. Vestibular nerve function was preserved in 10 patinets. Six patients had intentional sacrifice of vestibular function and
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ACCEPTED MANUSCRIPT Watanabe each of these patients ultimately recovered without long term balance difficulties. Similarly, the cochlear nerve function was preserved in all patients except those where it was intentionally
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sacrificed (cochlear schwannoma) and translabyrinthine approach.
Difficulty predicting pathology
Based on imaging, we were unable to predict the histopathology of any of the rare virgin tumors.
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Both schwannomas and meningiomas can be bright on T2 and homogeneously enhancing. The location and type of schwannoma is difficult to tell on imaging because of the small space in the
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IAC. Meningiomas, MALT lymphomas, and cavernous hemangiomas originate from the dura. Meningiomas typically have a dural tail and hyperostosis. However, when a small tumor grows in a crowded space, the dural tail may be obscured. MALT lymphomas originate from epithelial cells that are embryologically close to the meningotheilial arachnoid cells. Cavernous
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hemangiomas appear with different levels of intensity on MRI depending upon the age of blood manifested by different types of hemoglobin or hemosiderin products. Overall, the diagnosis of rare tumors on imaging is compromised by their relatively small size, location in a limited space,
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and proximity to intricate and variable anatomic structures [31-33]. Furthermore, clinical symptoms do not help much in forming a differential diagnosis since they are often based on
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mass effect, which occurs in both VSs and non-VSs.
Management of IAC tumors
None of the IAC tumors in this study had prior radiation. Management of IAC tumors to-date is largely based on patient and clinician preference. Most large (>2.5 cm) symptomatic IAC/CPA tumors are treated surgically. However, more controversy exists over small or medium sized
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ACCEPTED MANUSCRIPT Watanabe tumors. When clinical symptoms worsen, or when serial MRI imaging shows rapid tumor progression or size >25 mm diameter, a discussion of treatment options is often initiated. Options include radiosurgery, fractionated radiotherapy, or microsurgery [6, 7]. Several meta-analyses
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have compared the different modalities with mixed conclusions [6, 7, 34-43]. Radiosurgery and fractionated radiotherapy tend to be associated with a lower mortality rate and fewer cranial nerve deficits. However, there is a greater recurrence rate, requiring repeated treatments or
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ultimately microsurgery. At that point, radiated tissue and nearby eloquent anatomic structures
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are compromised, making surgery more challenging [44-46].
This poses a difficult challenge for clinical decision-making. Proceeding to radiosurgery or fractionated radiotherapy often occurs without histologic confirmation for the following reasons: 1) statistical likelihood of a tumor in the CPA or IAC being a VS, 2) difficulty of making an
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alternative diagnosis based on clinical symptoms or radiographic findings, 3) relative radiosensitivity of VSs, and 4) higher risks of microsurgery. While radiosurgery can be effective for VSs, rare tumors may benefit from microsurgery, with the goal of gross total resection dependent
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on intraoperative pathology.
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Obtaining a definitive histologic diagnosis can help guide further treatment during and after surgery. For example, for tumors that invade the cochlear cavity, a neurosurgeon can be more conservative if it is not a schwannoma. An intraoperative diagnosis of a meningioma can help redirect the neurosurgeon to the dural attachment for an optimal Simpson grade dissection. Aggressive MALT lymphomas can tolerate a subtotal resection since they are amenable to radiotherapy after microsurgery. However, lipochoristomas and cavernous hemangiomas should
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ACCEPTED MANUSCRIPT Watanabe be more aggressively managed surgically, since radiotherapy is not effective. Therefore, obtaining a definitive histologic diagnosis can improve both optimal dissections intraoperatively,
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and guide postoperative follow up treatment and surveillance.
CONCLUSION
In conclusion, our field’s understanding of IAC tumors is still growing. We present here 15
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additional cases of rare IAC tumors that contribute to an emerging body of literature describing non-vestibular schwannomas. Although approximately 95% of IAC tumors are vestibular
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schwannomas, MRI imaging is insufficient in most cases to predict actual pathology. Some of these tumors may be radiosensitive, but there is a trend towards treating small IAC tumors nonoperatively before a pathologic diagnosis. We are concerned that when surgical management is required, the potential compromise from prior radiation to these intricate tumors may handicap
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the surgeon’s ability to approach and resect this already technically challenging tumor. With clinical exam and imaging alone not sufficient to correctly identify these tumors, definitive
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pathological diagnosis should be strongly considered to help tailor treatment.
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ACCEPTED MANUSCRIPT Watanabe ACKNOWLEDGEMENTS: None FUNDING
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This research did not receive any specific grant from funding agencies in the public, commercial,
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or not-for profit sectors.
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FIGURE LEGENDS
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Figure 1: Facial Schwannoma
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[45]
Fig 1A: MRI T1-gad shows an enhanced tumor in the left IAC. Fig 1B: Via a left retrosigmoid approach, the superior vestibular nerve was normal.
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Fig 1C: The tumor originated from the facial nerve.
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IV = inferior vestibular nerve, SV = Superior vestibular nerve, FN = Facial nerve, Tu = Tumor
Figure 2: Cochlear Schwannoma Fig 2A: Via a right retrosigmoid approach, the superior and inferior vestibular nerves were normal
Fig 2B:After dividing between the vestibular nerves, the tumor appeared to be originating from the cochlear nerve.
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ACCEPTED MANUSCRIPT Watanabe Co = Cochlear nerve, IV = Inferior vestibular nerve, SV = Superior vestibular nerve, Tu = Tumor
Fig 3A: MRI T1-gad shows an IAC tumor.
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Figure 3: Intermedius Schwannoma
Fig 3B: Via a Right retrosigmoid approach, both superior and inferior vestibular nerves were resected. The tumor originated from the intermedius nerve.
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Fig 3C: After removing the tumor, the cochlear nerve and the facial nerve were intact.
Facial nerve, Tu = Tumor
Figure 4: Cavernous Hemangioma
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Fig 4A: Recurrent mass in the IAC, MRI T1-gad, axial
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Fig 4B: MRI T1-gad, coronal
Fig 4C: A T2-star MR image revealed an isointense tumor.
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Fig 4D: Via a left middle fossa approach, adherent tumor on the facial nerve was resected.
Figure 5: MALT Lymphoma
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Fig 5A: Enhancing mass stuffed in the IAC, seeming to originate from the dura mater, MRI T1gad, axial
Fig 5B: MRI T1-gad, coronal
Figure 6: Arachnoid Cyst Fig 6: Right middle fossa approach, after opening the internal auditory canal, revealed the
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ACCEPTED MANUSCRIPT Watanabe arachnoid cyst displacing the FN, VNs, and CN. AE = Arcuate eminence, FN = Facial nerve, VNs = Vestibular nerves, CN = Cochlear nerve,
Figure 7: Lipochoristoma
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GSPN = Greater superficial petrosal nerve
Fig 7A: A small mass lesion in the deep part of the IAC, MRI T1-gad axial
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Fig 7B: MRI CISS (Constructive interference in steady state) Fig 7C: Preoperative audiogram
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Fig 7D: Right retrosigmoid approach of the IAC showed a tumor attached to the inferior vestibular nerve. The superior vestibular nerve was intact.
Fig 7E: A tumor located in the deep fundus originating from the inferior vestibular nerve. Fig 7F: Variable mature adipocytes, mature fibrous tissue and tortuous thick walled vessel.
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Photomicrographic, H & E, original magnification x 100.
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ACCEPTED MANUSCRIPT Table 1: Demographics, Clinical Presentation, and Surgical Approach Pt
Age
Sex
Diag nosis
Cranial Nerve Function (baseline/postoperative) Facial Nerve
Vestibular Nerve
Approach
Follow up
Cochlear Nerve
40
F
FS
Intact/Intact
Vertigo, Dizziness, Tinnitis /Resolved at 1 mo
Sensorineural hearing loss/Stable
RS
4 yrs No recurrence
2
42
F
FS
Intact/Intact
Sensorineural hearing loss/Worsened
RS
8 yrs No recurrence
3
64
F
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Intact/HB VI post op, HB III at 1yr Intact/Intact
Tinnitus/Resolved
Mild sensorineural hearing loss/Improved
RS
7 yrs No recurrence
4
58
F
CS
Intact/Intact
Dizziness, Tinnitus/Resolved
Sensorineural hearing loss/ Hearing loss
MF
13 yrs No recurrence
5
53
F
NIS
Intact/Intact
Vertigo, Tinnitus /Resolved at 3 mo
Mild sensorineural hearing loss/Stable
RS
5 yrs No recurrence
6
36
M
NIS
Intact/ HB V postop, HB II at 1yr
Vertigo/Resolved
Mild sensorineural hearing loss/ Stable
RS
3 yr No recurrence
7*
66
M
Me
Intact/Intact
Tinnitus/Resolved
Sensorineural hearing loss/Worsened
MF
13 yrs No recurrence
8*
39
M
Me
Intact/ HB III postop, HB I at 1yr
Intact/Intact
Profound sensorineural hearing loss/Hearing loss
TL
10 yrs: No recurrence
9
58
M
Me
Intact/Intact
Vertigo/Resolved
Intact/Intact
RS
4 yrs: No recurrence
10
33
M
CH
Intact/Intact
Dizziness/Resolved
Sensorineural hearing loss/stable
1st RS
5 yrs: Recurrence
Intact/ HB IV post op, HB II at 6 mo
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immediate postop, worsened at 5 yrs
Intact/Intact
Sensorineural hearing loss/Hearing loss
2nd TL
7 yrs: Stable thin area of enhancement in IAC fundus
Intact/Intact
Sensorineural hearing loss/Stable
RS
1yr: No recurrence
66
M
CH
Intact/Intact
12
29
M
CH
Intact/Resolved
Sensorineural hearing loss/ Hearing loss
RS
2 yrs: No recurrence
13
45
M
ML
HB VI/ HB VI post op, HB III at 1yr Intact/Intact
Intact/Vertigo
Sensorineural hearing loss/Worsened
RS
1 yr: No recurrence
14
63
F
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Intact/Intact
Imbalance/Improved
Bilateral hearing loss/Stable
MF
10 yrs: No recurrence
15
48
M
LC
Intact/HB II postop, HB I at 1yr
Vertigo, Tinnitus/Improved
Intact/intact
RS
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1 yrs: No recurrence
*previously published case (Asaoka 2002) M = male, F = female, R = right, L = left, HB = House & Brackman, RS = Retrosigmoid approach, TL = Translabyrinthine approach, IAC = Internal auditory canal, MF = Middle fossa approach, AC = Arachnoid cyst, CH = Cavernous hemangioma, CS = Cochlear schwannoma, FS = Facial schwannoma, LC = Lipochoristoma, Me = Meningioma, ML = MALT lymphoma, NIS=Nervus intermedius schwannoma,
ACCEPTED MANUSCRIPT Table 2: IAC tumor characteristics Sid e
Size (mm)
MRI
Preoperativ e Diagnosis
Final Diagnosis
Description
Approach
1
L
2x4
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Facial schwannoma
Under superior and inferior vestibular nerve, Tumor was originated from facial nerve, which could be preserved because of small attachment.
RS
2
R
4x13
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Facial schwannoma
Fusiform adhered to facial nerve, between vestibular and cochlear nerve, removed with facial nerve, reanimated with sural nerve graft.
RS
3
R
2x4
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Cochlear schwannoma
Tumor located under superior and inferior vestibular nerves, attached to cochlear nerve.
RS
4
L
3x4
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Cochlear schwannoma
Ventral to inferior vestibular nerve, adhered to stretched cochlear nerve with difficulty visualizing continuation of cochlear nerve. ABR signal loss during dissection
MF
5
R
3x11
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Intermedius schwannoma
Originating from intermedius nerve, Superior and inferior vestibular nerve were divided and resected
RS
6
L
4x13
Cyst: T1W: hypointense T2W: hyperintense
Cystic Vestibular schwannoma
Intermedius schwannoma
Originated from intermedius nerve, anatomic preservation of facial nerve Superior and inferior vestibular nerve were sacrificed
RS
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Capsule: T1W isointense GdT1W: heterogeneous T2W: hypointense
L
3x12
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Meningioma (Psammomatous)
Vascular, adhered to rostral dura of IAC (Simpson Grade 2)
MF
8*
L
4x14
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Meningioma (Meningothelial)
Vascular, originate from rostral dura, adhered to facial nerve, invaded anterior petrosal bone. Greater superficial petrosal nerve was cut, facial nerve rerouted inferiorly
TL
9
L
2x3
T1W: isointense GdT1W: homogeneous
10
L
3x7
T1W: isointense GdT1W: homogeneous
L
3x10
T2*: isointense GdT1W: homogeneous
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7*
Meningioma (Meningothelial)
No adherent to nerves, tumor originate from the dura, the tumor removed with dura
RS
Vestibular schwannoma
Cavernous Hemangioma
Vessels originating from floor of IAC, tumor engulfed in cochlear and facial nerve, which were both preserved. Residual tumor in fundus.
1st RS
Tumor separated from facial nerve with thin residual near fundus. Vestibular and cochlear nerve sacrificed (from TL approach).
2nd TL
Cavernous Hemangioma
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Vestibular schwannoma
Cavernous Hemangioma
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Cavernous Hemangioma
Tumor separated from facial nerve and cochlear nerve. Vestibular nerves were anatomical intact.
RS
T1W: isointense GdT1W: heterogeneous
Cavernous hemangioma
Cavernous Hemangioma
RS
3x12
GdT1W: homogeneous Dural tail
Meningioma
MALT lymphoma
Tumor has high vascularity, and adhered facial and cochlear nerve. Vestibular nerves were sacrificed. The facial nerve was reconstructed with sural nerve Extended to fundus, with dural tail medial and lateral around porous area. Vestibular and cochlear nerve were sacrificed.
4.5x11
T1W: hypointense T2W: hyperintense GdT1W: no enhancement
Cystic lesion
Arachnoid cyst
CNs easily revealed and decompressed after arachnoid cyst wall was removed
MF
11
L
3x7
12
L
3x8
13
L
14
R
RS
2x4
T1W:isointensity-partial hyperintensity GdT1W: heterogeneous
It looks originate from the inferior vestibular Vestibular Lipochoristoma ACCEPTED MANUSCRIPT nerve. Facial nerve was intact. Vestibular schwannoma nerves were sacrificed. Facial nerve monitor was responded on the tumor with 0.2mA
*previously published case (Asaoka 2002)
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R = right, L = left, RS = Retrosigmoid approach, TL = Translabyrinthine approach, MF = Middle fossa approach, CNs = Cranial nerves,
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HIGHLIGHTS . • Rare internal auditory canal (IAC) tumors are poorly described • We describe 15 rare IAC tumors in 289 consecutive patients • Clinical exam and imaging alone were insufficient for correct diagnosis • Without tissue diagnosis, radiation may be ineffective or harmful • Tissue diagnosis of IAC tumors can help tailor further management
S1878-8750(16)31315-8
DOI:
10.1016/j.wneu.2016.12.003
Reference:
WNEU 4964
To appear in:
World Neurosurgery
Received Date: 26 August 2016 Revised Date:
1 December 2016
Accepted Date: 2 December 2016
Please cite this article as: Watanabe K, Huang Cobb MI-P, Zomorodi AR, Cunningham 3rd CD, Nonaka Y, Satoh S, Friedman AH, Fukushima T, Rare Lesions of the Internal Auditory Canal, World Neurosurgery (2017), doi: 10.1016/j.wneu.2016.12.003. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Watanabe TITLE PAGE
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Title: Rare Lesions of the Internal Auditory Canal
Authors: Kentaro Watanabe, M.D.1, 4, Mary In-Ping Huang Cobb, M.D.1, Ali R. Zomorodi
M.D.1, Calhoun D. Cunningham 3rd M.D.2, Yoichi Nonaka, M.D., PhD.1, 3, Shunsuke Satoh
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M.D.1, 5, Allan H. Friedman,M.D.1, Takanori Fukushima, M.D., D.M.Sc.1,
1
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Affiliations:
Department of Neurosurgery, Duke University Medical Center, 2301 Erwin Rd, Durham, NC,
27710, USA 2
Department of Surgery, Division of Head and Neck Surgery & Communication Sciences, Duke
Raleigh, NC 27609, USA 3
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University Medical Center, Duke Otolaryngology of Raleigh 3480 Wake Forest Road, Suite 404,
Department of Neurosurgery, Fukushima Takanori Skull Base Center, Shinyurigaoka General
Department of Neurosurgery, Hôpital Lariboisirère, Paris VII-Diderot University 2 rue
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Hospital, 255 Furusawa Aso-ku, Kawasaki, Kanagawa, 215-0026, Japan
Ambroise Pare, Paris, 75475 France 5
Department of Neurosurgery, Southern TOHOKU General Hospital, 7-115 Yatsuyamada,
Koriyama, Fukushima, 963-8052 Japan
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ACCEPTED MANUSCRIPT Watanabe Corresponding Author: Takanori FUKUSHIMA, M.D. DUMC Box 3807
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Durham, NC 27710 Phone: 919.239.0264 Fax: 919.239.0266
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Email: [email protected]
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Key words: internal auditory canal, acoustic neuroma, facial schwannoma, cochlear schwannoma, intermedius schwannoma, meningioma, cavernous hemangioma, MALT lymphoma, arachnoid cyst, lipochoristoma
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Abbreviations:
IAC: Internal auditory canal, RS: Retrosigmoid, MF: Middle fossa, TL: Translabyrinthine, MALT: Mucosa associated lymphoid tissue, MRI: Magnetic resonance imaging, CT: Computed
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tomography, VS: Vestibular schwannoma, CPA: Cerebellopontine angle, ENG: Electoronystagmography, ABR: Auditory brainstem response, PTA: Pure tone average, T1WI:
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T1 weighted image, T2WI: T2 weighted image, GdT1W: T1 with gadolinium contrast, CISS: Constructive interference in steady state, CSF: cerebrospinal fluid
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ACCEPTED MANUSCRIPT Watanabe ABSTRACT
Background: Approximately 95% of tumors occurring within the internal auditory canal (IAC)
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are vestibular schwannomas (VSs). Many undergo stereotactic radiation without definitive tissue diagnosis. Rare IAC tumors are not all radiosensitive and are poorly described. Methods: Between 1992 and 2015, 289 consecutive patients with IAC lesions operated on were
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retrospectively reviewed. Results: Fifteen patients (5.2%) (16 operations) had unusual
histological findings, including non-vestibular schwannomas (two facial schwannomas, two
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cochlear schwannomas, two intermedius schwannomas), three meningiomas, three cavernous hemangiomas, a mucosa associated lymphoid tissue (MALT) lymphoma, an arachnoid cyst, and a lipochoristoma. None of these rare tumors could be identified prior to surgery. Three operative approaches were used: retrosigmoid approach, middle fossa subtemporal approach, or
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translabyrinthine approach. Few complications occurred including facial nerve palsy, loss of hearing, and vestibular function. Five-year average follow up revealed one patient with recurrence. Conclusions: Clinical exam and imaging alone were insufficient to correctly identify
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treatment.
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these tumors. Definitive pathological diagnosis should be strongly considered to help tailor
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ACCEPTED MANUSCRIPT Watanabe INTRODUCTION
Approximately 10% of intracranial tumors occur in the internal auditory canal (IAC) and
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cerebellopontine angle (CPA). The vast majority (95%) of these tumors are vestibular
schwannomas (VSs). VSs originate from myelin-producing schwann cells of the vestibular
portion of the vestibulocochlear nerve [1]. Their overall incidence is rising, reaching 20 per
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million [2], with reasons investigated ranging from increased cell phone use, to improvements and overuse of diagnostic MRI studies [3-6]. Its benign natural history, with no growth or slow
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growth at 1-2 mm per year [7, 8] also contributes to its rising prevalence, estimated at 200 per million [9].
Not all tumors in the IAC and CPA are vestibular schwannomas. In the CPA, meningiomas and
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epidermoids are the next two most common tumors [10]. In the IAC, rare tumors that mimic VSs have been described in 4.3% of a 351-patient consecutive case series [11] and several other case studies. They include hybrid peripheral nerve sheath tumors [12], meningiomas [14-16],
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glioblastoma multiforme [17], metastases [18-20], primary adenocarcinoma [21], arachnoid cysts [22], lipomas [23, 24], lipochoristoma [25-27], melanoma [28, 29], and cavernous hemangiomas
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[10, 30].
With advances in neuroimaging technology, an increasing number of asymptomatic smaller tumors localized to the IAC are being detected. When small and medium sized tumors grow and become more symptomatic, they are often treated with radiosurgery or fractionated radiotherapy without histologic confirmation. However, if progressive enough to require microsurgery,
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ACCEPTED MANUSCRIPT Watanabe operating on radiated tissue is more challenging with almost certain risk of total hearing loss and increased risk of facial nerve paresis. Unusual lesions can be encountered in the IAC, which may not be radiosensitive. We describe here 15 rare IAC tumors that were surgically resected by the
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senior author (TF).
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MATERIALS AND METHODS
We searched retrospectively the clinical database from 1992 to 2015 for patients who underwent
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surgical management of IAC tumors (minimal to no extension into the CPA) by the principal investigator (TF) at four institutions (Duke University Medical Center, Durham, NC; WakeMed Hospital, Raleigh, NC; Southern Tohoku General Hospital, Fukushima, Japan; and Shin Komonji Hospital, Fukuoka, Japan). Surgeries were performed at Duke University Medical
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Center (Durham, NC), Southern Tohoku General Hospital (Fukushima, Japan), Moriyama Memorial Hospital (Tokyo, Japan), Shinyurigaoka General Hospital (Kanagawa, Japan), and Shinkomonji Hospital (Fukuoka, Japan). Approval was
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obtained from the Duke University Institutional Review Board along with a data
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transfer agreement from the four hospitals in Japan. Clinical charts were reviewed and data collected included demographics, clinical symptoms, MRI reports, pre-operative working diagnosis, pathologic diagnosis and descriptions, operative approach, and postoperative complications. Facial nerve palsy was classified using the House Brackman (HB) Scale. The retrosigmoid (RS) approach was used for resection of small to medium sized, proximally located tumors, with the goal of minimum exposure and hearing preservation. Subtemporal middle fossa (MF) approach was used for laterally located tumors filling the fundus, because it provided
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ACCEPTED MANUSCRIPT Watanabe optimal surgical exposure and angulation for tumor resection. The translabyrinthine (TL) approach was used to improve exposure for laterally placed tumors within the IAC, while sacrificing residual, non-serviceable hearing. Summative statistics were performed using MS
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Excel. Based on the small number of rare tumors, no further statistical analysis was performed.
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RESULTS
From 1992 to 2015, 289 consecutive patients who underwent surgical management of an IAC
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lesion by the senior author (TF) were retrospectively reviewed. Based on pathologic reports and operative notes, the majority of these patients had VSs (95%, 274/289). However, 15 of these patients (5.1%) had rare tumors. There were 8 males and 7 females with a mean age of 49.3±12 (Table 1). A total of 16 operations were performed on these 15 patients (one patient had an
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ipsilateral recurrence). Three different surgical approaches were taken, including RS (n = 11), MF (n = 3), and TL (n = 2). None of the patients received radiotherapy (Table 1). The follow up
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range is 1 to 13 years.
Clinical presentation
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Sensorineural hearing loss was the most common presenting symptom (n = 11), followed by tinnitus (n = 6), vertigo (n = 5), and dizziness (n = 4) (Table 1). One patient had baseline facial nerve palsy H & B Grade IV. (Table 1)
Facial Nerve First talk about the 3 patients where facial function was not preserved. In the 6 cases with new
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ACCEPTED MANUSCRIPT Watanabe postoperative facial nerve palsies, severity as measured by the HB scale improved to at least a grade III or lower by one year follow up. Two of these patients underwent a TL approach. The
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remaining four underwent a RS approach.
Two patients with adherent tumors underwent intraoperative resection of the facial nerve, followed by facial reanimation with a sural nerve graft. One of them had a facial nerve
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schwannoma. She developed a facial nerve palsy HB VI that recovered to III at one year followup (Patient #2). The other patient had a cavernous hemangioma with preoperative facial palsy
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HB grade IV that worsened to a grade VI postoperatively. He but recovered with nerve graft to a grade III with nerve graft at one year follow up (Patient #12).
The third case involved a nervus intermedius schwannoma with anatomic preservation of the facial nerve, but postoperatively developed a facial nerve palsy HBV that resolved to II at one
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year follow up (Patient #6).
The fourth case had an intracanalicular meningioma with anatomical preservation of the facial nerve, however postoperativly developed facial nerve palsy HB III that resolved to I at one year
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follow up. (Patient#8)
The fifth case involved a recurrent cavernous hemangioma operated via TL with facial response
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on the tumor on intraoperative neuromonitoring. However he developed a postoperative facial nerve palsy HB IV that recovered to HB II at 6 months follow-up (Patients#10). The last patient had a lipochoristoma with facial nerve response on intraoperative neuromonitoring. However, he developed a postoperative facial nerve palsy HB II that resolved to HB I at 4 months follow-up (Patient #15). Fortunately,the case of the small facial nerve schwannoma (Patient#1) did not have facial palsy
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ACCEPTED MANUSCRIPT Watanabe postoperativly because of the tumor and attachment of the tumor is small.
Vestibular Nerve
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The vestibular nerve was intentionally sacrificed in six cases. Two patients underwent a TL approach, and four underwent RS for tumors of the nervus intermedius, cochlear schwannoma, facial schwannoma, and cavernous hemangioma. All six patients demonstrated gradual
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improvement in balance function with no patient exhibiting disabling dizziness or balance
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problems.
Cochlear Nerve
In the majority of patients (11/16, 68.7 %), hearing function improved (n = 1), remained intact (n = 3), or stably diminished (n = 7). The cochlear nerve was intentionally sacrificed in two patients
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undergoing TL approach and one patient with a cochlear schwannoma. The remaining patients undergoing a MF (n = 2) and RS approach (n =2) had baseline hearing loss that worsened after
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surgery.
Imaging and histopathology
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Two-thirds of the cases (11/16, 68.6%) were assumed to be VS preoperatively (Table 2). Based on clinical symptoms and imaging, we were unable to predict the diagnosis of any patient for the initial operation. Final pathologic diagnoses of rare IAC tumors included 6 schwannomas originating from non-vestibular sources (2 facial schwannomas (Figure 1), 2 cochlear schwannomas (Figure 2), 2 intermedius schwannomas (Figure 3)), three meningiomas, three cavernous hemangioma (Figure 4), a mucosa associated lymphoid tissue lymphoma (MALT)
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Recurrence
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At a range of 1 to 13 year follow up, 14/15 patients had no recurrence (Table 1). Patient #10 had a recurrence at 5 years with re-resection followed by a stable thin area of enhancement in the
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IAC fundus at 7 year follow up.
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DISCUSSION
We describe here several rare tumors in the IAC. All types of tumors found in this study have been described in at least one other case study. Our rare tumor rate of 5.2% in 289 patients is comparable to the other large case series of 4.3% in 351 patients [12]. Given the limitations of
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two small case series, it is still interesting to note that the majority of our non-VS IAC cases were schwannomas from other origins (n = 6, 43%) compared to only one facial schwannoma in
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theirs. The majority of their non-VS cases were lipomas (n = 6, 40%) and we found none.
Postoperative Cranial Nerve Function
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Overall, patients in our case series had good preservation or improvement of baseline facial nerve, vestibular nerve, and cochlear nerve function. When excluding patients with strategies that were intended to sacrifice facial nerve function (e.g., intentional facial sacrifice with reanimation, or cases where the facial nerve was severely involved with the tumor), facial nerve function was noted to be normal or near normal in 86.7% of patients. Vestibular nerve function was preserved in 10 patinets. Six patients had intentional sacrifice of vestibular function and
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ACCEPTED MANUSCRIPT Watanabe each of these patients ultimately recovered without long term balance difficulties. Similarly, the cochlear nerve function was preserved in all patients except those where it was intentionally
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sacrificed (cochlear schwannoma) and translabyrinthine approach.
Difficulty predicting pathology
Based on imaging, we were unable to predict the histopathology of any of the rare virgin tumors.
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Both schwannomas and meningiomas can be bright on T2 and homogeneously enhancing. The location and type of schwannoma is difficult to tell on imaging because of the small space in the
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IAC. Meningiomas, MALT lymphomas, and cavernous hemangiomas originate from the dura. Meningiomas typically have a dural tail and hyperostosis. However, when a small tumor grows in a crowded space, the dural tail may be obscured. MALT lymphomas originate from epithelial cells that are embryologically close to the meningotheilial arachnoid cells. Cavernous
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hemangiomas appear with different levels of intensity on MRI depending upon the age of blood manifested by different types of hemoglobin or hemosiderin products. Overall, the diagnosis of rare tumors on imaging is compromised by their relatively small size, location in a limited space,
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and proximity to intricate and variable anatomic structures [31-33]. Furthermore, clinical symptoms do not help much in forming a differential diagnosis since they are often based on
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mass effect, which occurs in both VSs and non-VSs.
Management of IAC tumors
None of the IAC tumors in this study had prior radiation. Management of IAC tumors to-date is largely based on patient and clinician preference. Most large (>2.5 cm) symptomatic IAC/CPA tumors are treated surgically. However, more controversy exists over small or medium sized
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ACCEPTED MANUSCRIPT Watanabe tumors. When clinical symptoms worsen, or when serial MRI imaging shows rapid tumor progression or size >25 mm diameter, a discussion of treatment options is often initiated. Options include radiosurgery, fractionated radiotherapy, or microsurgery [6, 7]. Several meta-analyses
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have compared the different modalities with mixed conclusions [6, 7, 34-43]. Radiosurgery and fractionated radiotherapy tend to be associated with a lower mortality rate and fewer cranial nerve deficits. However, there is a greater recurrence rate, requiring repeated treatments or
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ultimately microsurgery. At that point, radiated tissue and nearby eloquent anatomic structures
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are compromised, making surgery more challenging [44-46].
This poses a difficult challenge for clinical decision-making. Proceeding to radiosurgery or fractionated radiotherapy often occurs without histologic confirmation for the following reasons: 1) statistical likelihood of a tumor in the CPA or IAC being a VS, 2) difficulty of making an
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alternative diagnosis based on clinical symptoms or radiographic findings, 3) relative radiosensitivity of VSs, and 4) higher risks of microsurgery. While radiosurgery can be effective for VSs, rare tumors may benefit from microsurgery, with the goal of gross total resection dependent
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Obtaining a definitive histologic diagnosis can help guide further treatment during and after surgery. For example, for tumors that invade the cochlear cavity, a neurosurgeon can be more conservative if it is not a schwannoma. An intraoperative diagnosis of a meningioma can help redirect the neurosurgeon to the dural attachment for an optimal Simpson grade dissection. Aggressive MALT lymphomas can tolerate a subtotal resection since they are amenable to radiotherapy after microsurgery. However, lipochoristomas and cavernous hemangiomas should
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and guide postoperative follow up treatment and surveillance.
CONCLUSION
In conclusion, our field’s understanding of IAC tumors is still growing. We present here 15
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additional cases of rare IAC tumors that contribute to an emerging body of literature describing non-vestibular schwannomas. Although approximately 95% of IAC tumors are vestibular
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schwannomas, MRI imaging is insufficient in most cases to predict actual pathology. Some of these tumors may be radiosensitive, but there is a trend towards treating small IAC tumors nonoperatively before a pathologic diagnosis. We are concerned that when surgical management is required, the potential compromise from prior radiation to these intricate tumors may handicap
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the surgeon’s ability to approach and resect this already technically challenging tumor. With clinical exam and imaging alone not sufficient to correctly identify these tumors, definitive
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pathological diagnosis should be strongly considered to help tailor treatment.
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ACCEPTED MANUSCRIPT Watanabe ACKNOWLEDGEMENTS: None FUNDING
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This research did not receive any specific grant from funding agencies in the public, commercial,
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or not-for profit sectors.
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ACCEPTED MANUSCRIPT Watanabe deterioration in healthy adults and is accompanied by local tumor control and a highly preserved quality of life (QOL) as patients' self-reported outcome. Radiother Oncol 2013;106(2):175-80. D'Astous M, Ho AL, Pendharkar A, Choi CY, Soltys SG, Gibbs IC, Tayag AT, Thompson PA, Adler JR, Chang SD. Stereotactic radiosurgery for non-vestibular cranial nerve schwanommas. J Neurooncol 2016. Kessel KA, Fischer H, Vogel MM, Oechsner M, Bier H, Meyer B, Combs SE. Fractionated vs. single-fraction stereotactic radiotherapy in patients with vestibular schwannoma : Hearing preservation and patients' self-reported outcome based on an established questionnaire. Strahlenther Onkol 2016. Roche PH, Regis J, Deveze A, Delsanti C, Thomassin JM, Pellet W. [Surgical removal of unilateral vestibular schwannomas after failed Gamma Knife radiosurgery]. Neurochirurgie 2004;50(2-3 Pt 2):383-93. Roche PH, Robitail S, Delsanti C, Marouf R, Pellet W, Regis J. [Radiosurgery of vestibular schwannomas after microsurgery and combined radio-microsurgery]. Neurochirurgie 2004;50(2-3 Pt 2):394-400. Roche PH, Robitail S, Pellet W, Deveze A, Thomassin JM, Regis J. [Results and indications of gamma knife radiosurgery for large vestibular schwannomas]. Neurochirurgie 2004;50(2-3 Pt 2):377-82.
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FIGURE LEGENDS
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Figure 1: Facial Schwannoma
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Fig 1A: MRI T1-gad shows an enhanced tumor in the left IAC. Fig 1B: Via a left retrosigmoid approach, the superior vestibular nerve was normal.
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Fig 1C: The tumor originated from the facial nerve.
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IV = inferior vestibular nerve, SV = Superior vestibular nerve, FN = Facial nerve, Tu = Tumor
Figure 2: Cochlear Schwannoma Fig 2A: Via a right retrosigmoid approach, the superior and inferior vestibular nerves were normal
Fig 2B:After dividing between the vestibular nerves, the tumor appeared to be originating from the cochlear nerve.
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ACCEPTED MANUSCRIPT Watanabe Co = Cochlear nerve, IV = Inferior vestibular nerve, SV = Superior vestibular nerve, Tu = Tumor
Fig 3A: MRI T1-gad shows an IAC tumor.
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Figure 3: Intermedius Schwannoma
Fig 3B: Via a Right retrosigmoid approach, both superior and inferior vestibular nerves were resected. The tumor originated from the intermedius nerve.
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Fig 3C: After removing the tumor, the cochlear nerve and the facial nerve were intact.
Facial nerve, Tu = Tumor
Figure 4: Cavernous Hemangioma
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NI = Nerves intermedius, IV = Inferior vestibular nerve, SV = Superior vestibular nerve, FN =
Fig 4A: Recurrent mass in the IAC, MRI T1-gad, axial
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Fig 4B: MRI T1-gad, coronal
Fig 4C: A T2-star MR image revealed an isointense tumor.
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Fig 4D: Via a left middle fossa approach, adherent tumor on the facial nerve was resected.
Figure 5: MALT Lymphoma
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Fig 5A: Enhancing mass stuffed in the IAC, seeming to originate from the dura mater, MRI T1gad, axial
Fig 5B: MRI T1-gad, coronal
Figure 6: Arachnoid Cyst Fig 6: Right middle fossa approach, after opening the internal auditory canal, revealed the
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ACCEPTED MANUSCRIPT Watanabe arachnoid cyst displacing the FN, VNs, and CN. AE = Arcuate eminence, FN = Facial nerve, VNs = Vestibular nerves, CN = Cochlear nerve,
Figure 7: Lipochoristoma
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GSPN = Greater superficial petrosal nerve
Fig 7A: A small mass lesion in the deep part of the IAC, MRI T1-gad axial
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Fig 7B: MRI CISS (Constructive interference in steady state) Fig 7C: Preoperative audiogram
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Fig 7D: Right retrosigmoid approach of the IAC showed a tumor attached to the inferior vestibular nerve. The superior vestibular nerve was intact.
Fig 7E: A tumor located in the deep fundus originating from the inferior vestibular nerve. Fig 7F: Variable mature adipocytes, mature fibrous tissue and tortuous thick walled vessel.
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Photomicrographic, H & E, original magnification x 100.
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ACCEPTED MANUSCRIPT Table 1: Demographics, Clinical Presentation, and Surgical Approach Pt
Age
Sex
Diag nosis
Cranial Nerve Function (baseline/postoperative) Facial Nerve
Vestibular Nerve
Approach
Follow up
Cochlear Nerve
40
F
FS
Intact/Intact
Vertigo, Dizziness, Tinnitis /Resolved at 1 mo
Sensorineural hearing loss/Stable
RS
4 yrs No recurrence
2
42
F
FS
Intact/Intact
Sensorineural hearing loss/Worsened
RS
8 yrs No recurrence
3
64
F
CS
Intact/HB VI post op, HB III at 1yr Intact/Intact
Tinnitus/Resolved
Mild sensorineural hearing loss/Improved
RS
7 yrs No recurrence
4
58
F
CS
Intact/Intact
Dizziness, Tinnitus/Resolved
Sensorineural hearing loss/ Hearing loss
MF
13 yrs No recurrence
5
53
F
NIS
Intact/Intact
Vertigo, Tinnitus /Resolved at 3 mo
Mild sensorineural hearing loss/Stable
RS
5 yrs No recurrence
6
36
M
NIS
Intact/ HB V postop, HB II at 1yr
Vertigo/Resolved
Mild sensorineural hearing loss/ Stable
RS
3 yr No recurrence
7*
66
M
Me
Intact/Intact
Tinnitus/Resolved
Sensorineural hearing loss/Worsened
MF
13 yrs No recurrence
8*
39
M
Me
Intact/ HB III postop, HB I at 1yr
Intact/Intact
Profound sensorineural hearing loss/Hearing loss
TL
10 yrs: No recurrence
9
58
M
Me
Intact/Intact
Vertigo/Resolved
Intact/Intact
RS
4 yrs: No recurrence
10
33
M
CH
Intact/Intact
Dizziness/Resolved
Sensorineural hearing loss/stable
1st RS
5 yrs: Recurrence
Intact/ HB IV post op, HB II at 6 mo
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immediate postop, worsened at 5 yrs
Intact/Intact
Sensorineural hearing loss/Hearing loss
2nd TL
7 yrs: Stable thin area of enhancement in IAC fundus
Intact/Intact
Sensorineural hearing loss/Stable
RS
1yr: No recurrence
66
M
CH
Intact/Intact
12
29
M
CH
Intact/Resolved
Sensorineural hearing loss/ Hearing loss
RS
2 yrs: No recurrence
13
45
M
ML
HB VI/ HB VI post op, HB III at 1yr Intact/Intact
Intact/Vertigo
Sensorineural hearing loss/Worsened
RS
1 yr: No recurrence
14
63
F
AC
Intact/Intact
Imbalance/Improved
Bilateral hearing loss/Stable
MF
10 yrs: No recurrence
15
48
M
LC
Intact/HB II postop, HB I at 1yr
Vertigo, Tinnitus/Improved
Intact/intact
RS
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1 yrs: No recurrence
*previously published case (Asaoka 2002) M = male, F = female, R = right, L = left, HB = House & Brackman, RS = Retrosigmoid approach, TL = Translabyrinthine approach, IAC = Internal auditory canal, MF = Middle fossa approach, AC = Arachnoid cyst, CH = Cavernous hemangioma, CS = Cochlear schwannoma, FS = Facial schwannoma, LC = Lipochoristoma, Me = Meningioma, ML = MALT lymphoma, NIS=Nervus intermedius schwannoma,
ACCEPTED MANUSCRIPT Table 2: IAC tumor characteristics Sid e
Size (mm)
MRI
Preoperativ e Diagnosis
Final Diagnosis
Description
Approach
1
L
2x4
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Facial schwannoma
Under superior and inferior vestibular nerve, Tumor was originated from facial nerve, which could be preserved because of small attachment.
RS
2
R
4x13
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Facial schwannoma
Fusiform adhered to facial nerve, between vestibular and cochlear nerve, removed with facial nerve, reanimated with sural nerve graft.
RS
3
R
2x4
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Cochlear schwannoma
Tumor located under superior and inferior vestibular nerves, attached to cochlear nerve.
RS
4
L
3x4
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Cochlear schwannoma
Ventral to inferior vestibular nerve, adhered to stretched cochlear nerve with difficulty visualizing continuation of cochlear nerve. ABR signal loss during dissection
MF
5
R
3x11
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Intermedius schwannoma
Originating from intermedius nerve, Superior and inferior vestibular nerve were divided and resected
RS
6
L
4x13
Cyst: T1W: hypointense T2W: hyperintense
Cystic Vestibular schwannoma
Intermedius schwannoma
Originated from intermedius nerve, anatomic preservation of facial nerve Superior and inferior vestibular nerve were sacrificed
RS
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Capsule: T1W isointense GdT1W: heterogeneous T2W: hypointense
L
3x12
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Meningioma (Psammomatous)
Vascular, adhered to rostral dura of IAC (Simpson Grade 2)
MF
8*
L
4x14
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Meningioma (Meningothelial)
Vascular, originate from rostral dura, adhered to facial nerve, invaded anterior petrosal bone. Greater superficial petrosal nerve was cut, facial nerve rerouted inferiorly
TL
9
L
2x3
T1W: isointense GdT1W: homogeneous
10
L
3x7
T1W: isointense GdT1W: homogeneous
L
3x10
T2*: isointense GdT1W: homogeneous
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7*
Meningioma (Meningothelial)
No adherent to nerves, tumor originate from the dura, the tumor removed with dura
RS
Vestibular schwannoma
Cavernous Hemangioma
Vessels originating from floor of IAC, tumor engulfed in cochlear and facial nerve, which were both preserved. Residual tumor in fundus.
1st RS
Tumor separated from facial nerve with thin residual near fundus. Vestibular and cochlear nerve sacrificed (from TL approach).
2nd TL
Cavernous Hemangioma
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Vestibular schwannoma
Cavernous Hemangioma
T1W: isointense GdT1W: homogeneous
Vestibular schwannoma
Cavernous Hemangioma
Tumor separated from facial nerve and cochlear nerve. Vestibular nerves were anatomical intact.
RS
T1W: isointense GdT1W: heterogeneous
Cavernous hemangioma
Cavernous Hemangioma
RS
3x12
GdT1W: homogeneous Dural tail
Meningioma
MALT lymphoma
Tumor has high vascularity, and adhered facial and cochlear nerve. Vestibular nerves were sacrificed. The facial nerve was reconstructed with sural nerve Extended to fundus, with dural tail medial and lateral around porous area. Vestibular and cochlear nerve were sacrificed.
4.5x11
T1W: hypointense T2W: hyperintense GdT1W: no enhancement
Cystic lesion
Arachnoid cyst
CNs easily revealed and decompressed after arachnoid cyst wall was removed
MF
11
L
3x7
12
L
3x8
13
L
14
R
RS
2x4
T1W:isointensity-partial hyperintensity GdT1W: heterogeneous
It looks originate from the inferior vestibular Vestibular Lipochoristoma ACCEPTED MANUSCRIPT nerve. Facial nerve was intact. Vestibular schwannoma nerves were sacrificed. Facial nerve monitor was responded on the tumor with 0.2mA
*previously published case (Asaoka 2002)
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R = right, L = left, RS = Retrosigmoid approach, TL = Translabyrinthine approach, MF = Middle fossa approach, CNs = Cranial nerves,
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HIGHLIGHTS . • Rare internal auditory canal (IAC) tumors are poorly described • We describe 15 rare IAC tumors in 289 consecutive patients • Clinical exam and imaging alone were insufficient for correct diagnosis • Without tissue diagnosis, radiation may be ineffective or harmful • Tissue diagnosis of IAC tumors can help tailor further management