Intrameatal Vestibular Schwannoma Research Articles

Macroscopic and microscopic changes of the vestibulocochlear nerve after Gamma Knife treatment

Wir berichten über einen Fall, bei dem makroskopische und mikroskopische Veränderungen des Verstibularnervs nach radiochirurgischer Behandlung eines intrameatalen Vestibularisschwannoms beobachtet wurden. Der Fallbericht zeigt das erste Mal ein morphologisches Korrelat der unerwünschten Effekte der Gamma-Knife-Therapie von Vestibularisschwannomen und unterstreicht, dass trotz eines deutlichen Abstands zum bestehenden Tumor degenerative Veränderungen der neuralen Strukturen erwartet werden können.

A microscope-assisted endoscopic transcanal transpromontorial approach for vestibular schwannoma resection: a preliminary report.

To evaluate the feasibility of a microscope-assisted endoscopic transcanal transpromontorial approach (METTA) for the removal of small vestibular schwannomas (VS) limited to the internal auditory canal (IAC), and introduce a modification without external auditory canal (EAC) closure. Between August 2018 and February 2019, seven patients with intrameatal VS underwent surgery in our center, endoscopic transcanal transpromontorial approach was applied in the first 2 patients and the rest 5 patients were operated via METTA. Treatment outcomes including efficacy of tumor resection, facial nerve outcome, operation time and post-operative course were recorded and analyzed. All seven patients were pathologically confirmed to have intrameatal VS. Total tumor removal was achieved in all cases. Two patients experienced cerebrospinal fluid leakage which resolved spontaneously within 5days. The average operation time was 161.41 ± 18.42min. All patients presented normal facial nerve function 1month after surgery. The METTA was effective in the removal of intrameatal VS. It can be an alternative surgical option for intrameatal VS with no serviceable hearing.

Meningiomas of the Internal Auditory Canal.

Identify and define specific preoperative and postoperative characteristics of intracanalicular meningiomas (ICMs) in order to improve their diagnosis and management, and to differentiate them from intrameatal vestibular schwannomas (IMVSs). Preoperative symptomatology, magnetic resonance imaging (MRI), and postoperative outcomes of 28 ICMs were analyzed. The results were compared to the literature and IMVSs treated by our group. Anacusis and progressive hearing loss were more frequent in the present population than the cases reviewed (P = .0064 and P = .0001, respectively). Hearing loss affected more than 90% of the patients, with anacusis in 32.1% of the cases. Facial palsy affected 17.9% of the patients. In comparison to IMVSs, preoperative anacusis was more associated to meningiomas (P = .0037), and the facial nerve was more compromised in ICMs than IMVSs, both preoperatively (P = .0011) and at follow-up (P < .0001). According to a re-evaluation of preoperative MRIs and comparison with IMVSs, linear tumor borders, and linear morphology along the internal auditory canal wall, but not the presence of a dural tail, were significantly more present in ICMs (P = .0035, P = .0004, P = .1963, respectively). These characteristics could have led to a correct preoperative diagnosis in 61% of our cases. Contrariwise to IMVSs, the frequent preoperative anacusis and facial palsy demonstrate the more aggressive nature of ICMs, which also carry a higher risk of postoperative facial palsy and difficulty to preserve hearing. An attentive evaluation of imaging should ease diagnosis, and asymptomatic or stable ICMs should be enrolled in a wait-and-scan protocol. 4 Laryngoscope, 131:E413-E419, 2021.

Suction Spatula for Surgery of Vestibular Schwannomas in Supine Position: Technical Note

Resection of vestibular schwannomas with good functional outcome remains a neurosurgical challenge. In this study, we report on our initial experience with a suction spatula, which allows free bimanual dissection of small tumors in a clear, bloodless surgical field in supine position. Forty-one patients underwent vestibular schwannoma surgery in supine position, using a suction spatula. To analyze its feasibility, 11 aspects of the device were compared with the regular retractor. The suction spatula was successfully applied in all surgeries. Compared with a common spatula, the suction spatula showed superior performance during meatotomy, microsurgical and endoscopic tumor dissection, and management of bleedings. We noted no difference in ergonomics, compatibility, instrumental conflict, costs, reusability, and sterilization issues. Minor performance was related to its thickness/size. There were no significant disadvantages according to our data. There were no surgical complications related to this device. The main advantage of the suction spatula is in the treatment of small, mainly intrameatal vestibular schwannomas in supine patient position. It gives the surgeon a "third hand" while enabling a continuous bimanual dissection with 2 microinstruments without the use of a regular suction tip.

Three-dimensional imaging of the human internal acoustic canal and arachnoid cistern: a synchrotron study with clinical implications.

A thorough knowledge of the gross and micro‐anatomy of the human internal acoustic canal (IAC) is essential in vestibular schwannoma removal, cochlear implantation (CI) surgery, vestibular nerve section, and decompression procedures. Here, we analyzed the acoustic‐facial cistern of the human IAC, including nerves and anastomoses using synchrotron phase contrast imaging (SR‐PCI). A total of 26 fresh human temporal bones underwent SR‐PCI. Data were processed using volume‐rendering software to create three‐dimensional (3D) reconstructions allowing soft tissue analyses, orthogonal sectioning, and cropping. A scalar opacity mapping tool was used to enhance tissue surface borders, and anatomical structures were color‐labeled for improved 3D comprehension of the soft tissues. SR‐PCI reproduced, for the first time, the variable 3D anatomy of the human IAC, including cranial nerve complexes, anastomoses, and arachnoid membrane invagination (acoustic‐facial cistern; an extension of the cerebellopontine cistern) in unprocessed, un‐decalcified specimens. An unrecognized system of arachnoid pillars and trabeculae was found to extend between the arachnoid and cranial nerves. We confirmed earlier findings that intra‐meatal vestibular schwannoma may grow unseparated from adjacent nerves without duplication of the arachnoid layers. The arachnoid pillars may support and stabilize cranial nerves in the IAC and could also play a role in local fluid hydrodynamics.

An international comparison of diagnostic and management strategies for vestibular schwannoma

ObjectiveTo compare international diagnostic and management strategies for vestibular schwannoma (VS).MethodsA web-based questionnaire was sent to 130 otolaryngologists, mainly identified through the European Skull Base Society. It contained questions on general information including guideline usage as well as questions on diagnosis (focussing on selection of patients for MRI) and management of VS, including case scenarios. Descriptive statistics were reported.ResultsThirty-six otolaryngologists working in 11 different countries completed the questionnaire (response rate: 28%). Guidelines for diagnosis and management of VS are used by 44% and 42% of respondents, respectively. In the diagnostic strategy for VS, different types and combinations of audiovestibular function tests are used when deciding whether a patient should undergo an MRI. Respondents apply 18 different definitions of asymmetrical hearing loss. Variation was also apparent from reported considerations on management of VS. Most respondents (84%) prefer a wait-and-scan strategy in case of a small intrameatal VS (Koos 1). Variety in management strategies increases for patients with a medium to large sized VS (Koos 2, 3 and 4). The details of each management strategy (wait-and-scan, microsurgery, stereotactic radiosurgery and fractionated radiotherapy) also differ among respondents.ConclusionsA large variation in diagnostic and management strategies for VS was identified between respondents. More evidence and/or consensus seem warranted to reduce uncertainties for patients, and differences in outcome and costs that might result from the variety of strategies currently being applied.

VIIIth nerve cavernous hemangioma mimicking a stage 1 acoustic schwannoma

ObjectiveTo report a case of VIIIth nerve cavernous hemangioma, a very rare differential diagnosis among the various pathologies presenting as small enhancing entities into the internal auditory canal. It is one of the most challenging when imaging is not able to differentiate it from an intrameatal vestibular schwannoma. Methods and resultsWe report a cavernous hemangioma extruding from the internal auditory canal, diagnosed after a left translabyrinthine resection in a 45-year-old man complaining of profound sensorineural hearing loss, with no facial paresis or dizziness. The preoperative differential diagnosis of a vestibular schwannoma was impossible, due to the absence of calcifications that usually characterize temporal bone hemangiomas. Clinical presentation, radiological features and treatment considerations are discussed along with up-to-date review of pertinent literature. ConclusionsWhen considering an apparent small intra-auditory canal schwannoma, otoneurologists should be aware of the rare possibility of a cavernous hemangioma. Early diagnosis and surgical treatment may improve the functional outcome, possibly preserving neural integrity.

Distinct spontaneous shrinkage of a sporadic vestibular schwannoma

We present a case with outspoken spontaneous vestibular schwannoma shrinkage and review the related literature. The patient was initially diagnosed with a left-sided, intrameatal vestibular schwannoma, which subsequently grew into the cerebello-pontine angle (CPA), followed by total shrinkage of the CPA component without any intervention over a 12-year observation period. The literature on spontaneous tumor shrinkage was retrieved by searching the subject terms "vestibular schwannoma, conservative management" in PubMed/MEDLINE database, without a time limit. Of the published data, the articles on "shrinkage" or "negative growth" or "regression" or "involution" of the tumor were selected, and the contents on the rate, extent and mechanism of spontaneous tumor shrinkage were extracted and reviewed. The reported rate of spontaneous shrinkage of vestibular schwannoma is 5-10% of patients managed conservatively. Extreme shrinkage of the tumor may occur spontaneously.

Vestibular Schwannoma

In vestibular schwannoma (VS) surgery, the arachnoidal duplication, based on an epiarachnoidal origin of the tumor, is reputedly induced by medial growth of tumor and helpful in atraumatic dissection. This study was intended to verify the epiarachnoidal origin of VS. We studied 49 human temporal bones (TBs) specimens. Twenty-two TBs from 18 patients with VS were selected. An additional series of 27 TBs without any tumor within the internal auditory meatus were also included. We identified the location of the meninges and the position of the transition zone inside the meatus and described the lateral extension of the subarachnoid spaces. In VS specimens, psammoma bodies were seen at the fundus along the arachnoidal layer. No connective tissue or protrusion of a psammoma body was observed between the nerves and the VS. High magnification failed to demonstrate any meningeal cleavage plane between the facial or cochlear nerve and the tumor. The subarachnoid space was visible within the internal auditory meatus and extended from the porus to the fundus. In every case, the transition zone, the vestibular ganglion, or the VS was located in the subarachnoid fluid space. We were not able to identify any layer between tumor and the intrameatal contents and did not observe any conjunctive-tissue capsule surrounding the intrameatal VS, as an epiarachnoidal tumor origin would suggest. These observations are in contradiction with the descriptions concerning the epiarachnoidal origin of VS.

Cavernous angiomas within the internal auditory canal

The aim of this study was to describe the symptomatology, radiological features, and surgical treatment of patients with cavernous angiomas within the internal auditory canal (IAC). The authors reviewed the cases of seven patients with cavernous angiomas in the IAC that had been surgically treated in the 22-year period between 1983 and 2005. All the patients had presented with sensorineural hearing loss, and four suffered from tinnitus. Four patients also reported facial symptoms such as hemispasm or progressive palsy; one of these patients had presented with sudden facial paresis due to intrameatal tumor hemorrhage. According to computed tomography (CT) results, the lesions caused enlargement of the IAC. Interestingly, these same angiomas showed variable features on magnetic resonance (MR) imaging, making their differentiation from intrameatal vestibular schwannomas (VSs) sometimes impossible. In all patients the lesions were totally removed via the suboccipital retrosigmoid approach. They could be dissected away from the facial nerve in five cases, whereas in two cases, because of the location of the lesion, the seventh cranial nerve had to be sectioned and repaired with a sural nerve graft. Transient worsening of seventh cranial nerve symptoms occurred in two patients, with postoperative improvement in each of them. The cochlear nerve could not be functionally preserved because of its extreme adherence to the tumor, although its continuity was preserved in four patients. Complete deafness was the only postoperative complication. Cavernous angiomas of the IAC are very uncommon lesions that can imitate the symptoms of VSs. Although it is the most sensitive study available, MR imaging does not show sufficiently specific findings to differentiate the two lesion types. Thus, the preoperative diagnosis must be based on patient symptoms plus the CT and MR imaging features.

Endoscope-Controlled Removal of Intrameatal Vestibular Schwannomas

The use of endoscopes for surgery of the cerebellopontine angle tumors is steadily obtaining widespread acceptance. The objective of the present study was a laboratory and clinical evaluation of the safety of the endoscope-controlled microneurosurgical removal of the intrameatal vestibular schwannomas through a retrosigmoid approach. The anatomical investigation was done on formalin-fixed cadaver heads and dry temporal bones. Clinical series included 33 consecutive patients (23 women and 10 men; mean age 50 +/- 15 years). A bayonet-style rigid endoscope with 70 degrees angle of view and 4 mm outer diameter was found to be optimal for observation of the internal auditory canal. Its insertion in the cerebellopontine cistern should be preferably done under control through an operating microscope. Endoscope-controlled manipulations necessitate the use of a special holder system, which provides a stable position of the device and allows bimanual manipulations by the surgeon. A thermographic evaluation did not reveal a significant increase of the local temperature due to use of the endoscope. Use of the endoscope permitted removal of the neoplasm from the most lateral part of the internal auditory canal and identification of the nerve of tumor origin. In total, 28 tumors underwent total removal, and anatomical preservation of the facial nerve was attained in 31 cases. Damage of the facial nerve by the endoscope was met once. In 8 out of 16 patients, who showed serviceable hearing before surgery, this was preserved after tumor removal. In conclusion, endoscope-controlled removal of the intrameatal vestibular schwannomas seems to be a technically feasible, effective and safe procedure. Nevertheless, good equipment and special training are absolutely necessary for attainment of optimal results.

Is Navigation Useful in the Resection of Small Intrametal Vestibular Schwannomas?

Introduction: Navigation is generally accepted as an optional additional procedure in skull base surgery. The precise imaging by MR and CT and the correct transforming of these data by the referencing procedure of the navigation system is mandatory. Due to individual differences of the petrous bone it is sometimes difficult to identify the anatomical landmarks near the inner ear canal. Therefore the use of navigation can reduce drill work to progress directly to the optimal target point of uncovering the inner ear canal in small intrameatal vestibular schwannomas (stage I and II, grade 1, 2, or 3 according to Zini and Magnan) by navigation.

Meningiomas of the internal auditory canal.

Meningiomas arising primarily within the internal auditory canal (IAC) are notably rare. By far the most common tumors that are encountered in this region are neuromas. We report a series of eight patients with meningiomas of the IAC, analyzing the clinical presentations, surgical management strategies, and clinical outcomes. The charts of the patients, including histories and audiograms, imaging studies, surgical records, discharge letters, histological records, and follow-up records, were reviewed. One thousand eight hundred meningiomas were operated on between 1978 and 2002 at the Neurosurgical Department of Nordstadt Hospital. Among them, there were 421 cerebellopontine angle meningiomas; 7 of these (1.7% of cerebellopontine angle meningiomas) were limited to the IAC. One additional patient underwent surgery at the Neurosurgical Department of the International Neuroscience Institute, where a total of 21 cerebellopontine angle meningiomas were treated surgically from 2001 to 2003. As a comparison, the incidence of intrameatal vestibular schwannomas during the same period, 1978 to 2002, was 168 of 2400 (7%). There were five women and three men, and the mean age was 49.3 years (range, 27-59 yr). Most patients had signs and symptoms of vestibulocochlear nerve disturbance at presentation. One patient had sought treatment previously for total hearing loss before surgery. No patient had a facial paresis at presentation. The neuroradiological workup revealed a homogeneously contrast-enhancing tumor on magnetic resonance imaging in all patients with hypointense or isointense signal intensity on T1- and T2-weighted images. Some intrameatal meningiomas showed broad attachment, and some showed a dural tail at the porus. In all patients, the tumor was removed through the lateral suboccipital retrosigmoid approach with drilling of the posterior wall of the IAC. Total removal was achieved in all cases. Severe infiltration of the facial and vestibulocochlear nerve was encountered in two patients. There was no operative mortality. Hearing was preserved in five of seven patients; one patient was deaf before surgery. Postoperative facial weakness was encountered temporarily in one patient. Although intrameatal meningiomas are quite rare, they must be considered in the differential diagnosis of intrameatal mass lesions. The clinical symptoms are very similar to those of vestibular schwannomas. A radiological differentiation from vestibular schwannomas is not always possible. Surgical removal of intrameatal meningiomas should aim at wide excision, including involved dura and bone, to prevent recurrences. The variation in the anatomy of the faciocochlear nerve bundle in relation to the tumor has to be kept in mind, and preservation of these structures should be the goal in every case.

Trigeminal root recording in normal trigeminal function.

Despite many investigations on the detection of trigeminal evoked potentials (TEP), there is still no consensus on a technique or interpretation of its components. In order to obtain clear TEP waveforms and analyze the origin of early components, we recorded TEP by the conventional far-field technique at the ipsilateral auricula as well as by near-field technique with a bipolar electrode at the trigeminal root just distal to the entry zone of its root. Trigeminal recordings were performed in nine patients with intrameatal vestibular schwannomas and in three with trigeminal neuralgia without trigeminal nerve deficits. In near-field recording at the trigeminal root, a triphasic response was recorded, with the first component occurring at 3.16 ms, 2.98 ms, and 4.16 ms following supraorbital, infraorbital, and mandibular nerve stimulation, respectively. Using conventional farfield TEP, the first component recorded at the trigeminal root occurred later than the first component in all other recordings. This suggests that the N2.0 component of far-field TEP is of extra-axial origin and the N5 component is of brainstem origin. The N13.0 component may be of cortical origin. We conclude that the N5.0 component and N5.0-N13.0 interpeak latency may be used as electrophysiological parameters of brainstem function during posterior fossa surgery.

Intracanalicular Vestibular Schwannoma - Therapeutic Options

The growth of purely intrameatal vestibular schwannoma (VS) was investigated in a series of 40 patients with 40 unilateral VS in the period 1973 to 1996 (mean 3.6 years). Twenty-seven tumours (67.5%) revealed growth and 13 tumours (32%) had no measurable growth. Four growth patterns were observed: (i) 15 tumours (37.5%) exhibited constant growth; (ii) 13 tumours (32.5%) had no measurable growth; (iii) 8 tumours (20%) revealed growth subsequent to a no-growth period; and (iv) 4 tumours (10%) manifested different growth patterns during the observation period. The mean diameter growth per year was 3.2 mm. The findings of the present study, especially those achieved in groups B (the non-growing tumours) and C (tumour growth subsequent to a silent period), question the reliability of the results achieved by radiosurgery, as no tumour growth may occur with no intervention.

Management of Intrameatal Vestibular Schwannoma: Microsurgery, Radiosurgery or "Wait and Scan"

The growth of purely intrameatal vestibular schwannoma (VS) was investigated, in the period 1973-96 in a series of 40 patients with 40 unilateral VS. In the present study, the material was analysed and updated. By the end of the observation period (mean 3.6 years), 27 tumours (67.5%) revealed growth and 13 tumours (32%) had no measurable growth. Four growth patterns were observed: (A) 15 tumours (37.5%) exhibited constant growth; (B) 13 tumours (32.5%) had no measurable growth; (C) 8 tumours (20%) revealed growth subsequent to a no-growth period; and (D) 4 tumours (10%) showed different growth patterns during the observation period. The annual diameter growth rate ranged between 00 mm/year and 6.5 mm/year and the mean diameter growth per year was 3.2 mm. The findings of the present study, especially those for group B (the non-growing tumours) and C (tumour growth subsequent to a silent period) bring into question the reliability of the results achieved by radiosurgery, as without any intervention it may be that no tumour growth occurs.