The local ethical committee approved the publication of this clinical case. A written informed consent form was collected from the patient.
1. Clinical and audiological evaluation
<ol>
	<li>Collect personal or familiar history of VHL disease or compatible symptoms from the patient.</li>
	<li>Perform a neurological examination to investigate central causes. Ensure that there is no pathological cause to be underlined and the facial nerve function is normal.</li>
	<li>Assess external, middle, and inner ear functionality and assess whether a complete audiological and otoneurological evaluation is necessary.</li>
	<li>After a bilaterally negative otoscopy, perform a hearing assessment using a pure tone and vocal audiometry with a classical clinical audiometer and a tympanometry with stapedial reflex study with a clinical tympanometry.</li>
</ol>
2. Imaging study
<ol>
	<li>Perform an MRI to further exclude other causes of vertigo and to study the internal auditory canal (IAC) and pontocerebellar angle (PCA), 2 days after the hospitalization.
	<ol>
		<li>Use a 1.5 T MRI system equipped with an 8-channel phased array head coil to perform the brain, brainstem, and petrous bone examination.</li>
		<li>For the MRI examination protocol, use axial fluid-attenuated inversion recovery and axial fast spin-echo T2-weighted sequences. Target steady-state free precession (SSFP) images with a FIESTA (Fast Imaging Employing Steady-state Acquisition) sequence on the inner ear. Acquire high-resolution volumetric images with T1-weighted SPGR (Spoiled Gradient-Recalled) sequence before and after contrast media administration.</li>
	</ol>
	</li>
	<li>Perform a high-resolution computer tomography (HRCT) of the petrous bone, with a 64-slice scan to confirm the presence of any isodense mass.</li>
	<li>After the execution of the MRI and the HRCT, define the grading of the tumor and plan the surgical approach for the mass resection. Discuss the prognosis of the surgery and the disease with the patient.</li>
</ol>
3. Surgical management
<ol>
	<li>Twenty-four hours before the surgery, have an experienced interventional neuroradiologist perform an arterial&#160;embolization of the mass on a biplane angiograph.</li>
	<li>Perform the embolization with poly vinyl alcohol particles of 150-250 microns size with selective catheterization of the feeding vessels.</li>
	<li>If as in this case, there is limited extension of the tumor but a relevant hearing deficit, schedule a surgical resection of the mass through a translabirinthine approach to be performed by a 25 years-experienced surgeon of the ear and the lateral skull base.</li>
	<li>After a C-shaped retroauricolar incision and the raising of a temporalis muscle&#39;s flap, perform an ample mastoidectomy with a Striker S2 &#960;Drive drilling system.
	<ol>
		<li>Cut round precision and fluted tips, as well as coarse and fine diamond round tips, depending on the drilled structures.</li>
		<li>Expose the sigmoid sinus and the dura of the middle cranial fossa posteriorly and superiorly, respectively.</li>
		<li>Complete an ample antrotomy with a complete exposure of the small process of the incus and then, prepare a posterior tympanotomy.</li>
		<li>Drill out all the retro-facial mastoid cells up to the mastoid tip, until the identification of the jugular bulb.</li>
		<li>Complete the posterior labyrinthectomy with semicircular canals until the identification of the internal auditory canal (IAC).</li>
		<li>Identify the neoplasm after the complete exposure of the dura of the middle and posterior cranial fossa, in the endolymphatic sac area. If the the neoplasm is indivisible from the dura of the posterior cranial fossa, cut the dura and remove it en-bloc with the tumor. If the neoplasm has reached and invaded the IAC, open the IAC to completely remove the tumor.</li>
	</ol>
	</li>
	<li>Conduct an intraoperative extemporaneous histological examination.</li>
	<li>Seal the posterior tympanotomy and the antrotomy with surgical wax, and fill the ample mastoid cavity with autologous abdominal fat and fibrin glue.</li>
	<li>Check for post-surgical cerebrospinal fluid (CSF) leak and assess the blood loss due to surgery.</li>
</ol>
4. Postsurgical course
<ol>
	<li>In the post-operatory course, check for vertigo, residual hearing, CSF leakages, and facial nerve palsy among other complications.</li>
</ol>

<ol>
	<li>Heffner, D. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-grade+adenocarcinoma+of+probable+endolymphatic+sac+origin+A+clinicopathologic+study+of+20+cases.">Low-grade adenocarcinoma of probable endolymphatic sac origin A clinicopathologic study of 20 cases.</a> Cancer. 64 (11), 2292-2302 (1989).</li><li>Lonser, R. R., Baggenstos, M., Kim, H. J., Butman, J. A., Vortmeyer, A. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+vestibular+aqueduct:+site+of+origin+of+endolymphatic+sac+tumors.">The vestibular aqueduct: site of origin of endolymphatic sac tumors.</a> J Neurosurg. 108 (4), 751-756 (2008).</li><li>Megerian, C. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endolymphatic+sac+tumors:+histopathologic+confirmation,+clinical+characterization,+and+implication+in+von+Hippel-Lindau+disease.">Endolymphatic sac tumors: histopathologic confirmation, clinical characterization, and implication in von Hippel-Lindau disease.</a> Laryngoscope. 105, 801-808 (1995).</li><li>Zanoletti, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endolymphatic+sac+tumour+in+von+Hippel-Lindau+disease:+management+strategies.">Endolymphatic sac tumour in von Hippel-Lindau disease: management strategies.</a> Acta Otorhinolaryngol Ital. 37 (5), 423-429 (2017).</li><li>Mendenhall, W. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+Treatment+of+Endolymphatic+Sac+Tumor+of+the+Temporal+Bone.">Current Treatment of Endolymphatic Sac Tumor of the Temporal Bone.</a> Adv Ther. 35 (7), 887-898 (2018).</li><li>Wu, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surgical+management+of+endolymphatic+sac+tumor:+classification,+outcomes+and+strategy.+A+single+institution's+experience.">Surgical management of endolymphatic sac tumor: classification, outcomes and strategy. A single institution's experience.</a> Eur Arch Otorhinolaryngol. , (2022).</li><li>Bausch, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+endolymphatic+sac+tumors+and+von+Hippel-Lindau+disease+in+the+International+Endolymphatic+Sac+Tumor+Registry.">Characterization of endolymphatic sac tumors and von Hippel-Lindau disease in the International Endolymphatic Sac Tumor Registry.</a> Head Neck. 38, E673-E679 (2016).</li><li>Tang, J. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systematic+Review+of+Endolymphatic+Sac+Tumor+Treatment+and+Outcomes.">Systematic Review of Endolymphatic Sac Tumor Treatment and Outcomes.</a> Otolaryngol Head Neck Surg. , (2022).</li><li>Balasubramaniam, S., Deshpande, R. B., Misra, B. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gamma+knife+radiosurgery+in+jugular+foramen+endolymphatic+sac+adenocarcinoma.">Gamma knife radiosurgery in jugular foramen endolymphatic sac adenocarcinoma.</a> J Clin Neurosci. 16 (5), 710-711 (2009).</li><li>Poletti, A. M., Dubey, S. P., Colombo, G., Cugini, G., Mazzoni, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Treatment+of+endolymphatic+sac+tumour+(Papillary+adenocarcinoma)+of+the+temporal+bone.">Treatment of endolymphatic sac tumour (Papillary adenocarcinoma) of the temporal bone.</a> Rep Pract Oncol Radiother. 21 (4), 391-394 (2016).</li><li>Bambakidis, N. C., Megerian, C. A., Ratcheson, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+grading+of+endolymphatic+sac+tumor+extension+by+virtue+of+von+Hippel-Lindau+disease+status.">Differential grading of endolymphatic sac tumor extension by virtue of von Hippel-Lindau disease status.</a> Otol Neurotol. 25 (5), 773-781 (2004).</li><li>Schipper, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endolymphatic+sac+tumours:+surgical+management.">Endolymphatic sac tumours: surgical management.</a> J Otolaryngol. 35 (6), 387-394 (2006).</li><li>Li, F., Zhang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grading+system+and+surgical+approaches+for+endolymphatic+sac+tumors.">Grading system and surgical approaches for endolymphatic sac tumors.</a> Arch Otorhinolaryngol. 278 (5), 1345-1353 (2021).</li><li>Chittiboina, P., Lonser, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Von+Hippel-Lindau+disease.">Von Hippel-Lindau disease.</a> Handb Clin Neurol. 132, 139-156 (2015).</li><li>Sykopetrites, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+endolymphatic+sac+tumor:+challenges+in+the+eradication+of+a+localized+disease.">The endolymphatic sac tumor: challenges in the eradication of a localized disease.</a> Eur Arch Otorhinolaryngol. 278 (7), 2297-2304 (2021).</li><li>Devaney, K. O., Ferlito, A., Rinaldo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endolymphatic+sac+tumor+(low-grade+papillary+adenocarcinoma)+of+the+temporal+bone.">Endolymphatic sac tumor (low-grade papillary adenocarcinoma) of the temporal bone.</a> Acta Otolaryngol. 123 (9), 1022-1026 (2003).</li></ol>

The authors declare no conflicts of interest.

ELST are rare and locally aggressive neoplasms that arise on the posteromedial surface of the temporal bone. Due to their slow growth rate, and the initial paucity of the symptoms, the diagnosis is often delayed, resulting in an advanced tumor stage. Since the surgery morbidity as well as the oncologic outcomes are strongly correlated with the tumor dimensions and extension6,8,13,15, an early diagnosis is necessary. 
The first step for a prompt diagnosis is the clinical evaluation of patients. The medical and familiar history of a patient that may refer to the presence of a VHL has to be thoroughly investigated. Anyway, in the case reported herein, no history of known VHL was reported from the patient, as well as previous suggestive symptoms.
Further, since hearing loss and vertigo are a frequent association of symptoms underlying a number of peripheric clinical conditions of the ear, ranging from hydropic diseases of the inner ear to the acute unilateral vestibulopathy, but also central disturbances, is important to rule out neurological and neuroradiologic examinations in every patient reporting Meniere-like symptoms. In fact, even when the clinical picture seems to indicate a pure peripheric lesion, an imaging study of the brain, the brainstem, and the petrous bones should be always advised, even to exclude central diseases leading to peripheric deficit, but, mainly, for the study of IAC and the PCA. Those aspects are even more important when a patient presents a confirmed diagnosis of VHL or occurrences compatible with such a disease.
In the case herein reported, the diagnosis was appropriately suspected based on a rapid imaging study after the symptom's onset and intraoperatively confirmed shortly afterward. As shown here, an early diagnosis based on the clinical signs and symptoms and prompt imaging studies can lead to a more sustainable surgery, with low risk of postoperative residuals or recurrence of disease.
Even if hearing loss and vertigo are a frequent association of symptoms underlying many peripheric clinical conditions of the ear, neuroradiologic examination have to be promptly ruled out to exclude misdiagnosed central disturbances, as well as IAC or PCA diseases. Furthermore, an accurate anamnesis should investigate for occurrences that are compatible with VHL, such as prior diagnosis of tumors such as pheochromocytoma, cerebellar hemangioblastoma, or retinal angioma; prior comparison of cysts at kidneys, liver, pancreas, or genital tract; and symptoms like headache, asthenia, hypertension, ataxia, or vision disturbances14. 
In our third level referral hospital, all the patients reporting cochlear or vestibular symptoms promptly undergo an imaging study, preferably a high-field MRI study of the brain and the brainstem and the petrous bone with contrast agent, for an accurate evaluation of those structures, the IAC and the PCA, and a HRCT scan study, for the evaluation of the bony structures of the petrous bone, if needed. The occurrence of a mass arising from the posterior face of the petrous bone, especially if associated with a suspected or known diagnosis of VHL, is highly suggestive of ELST. 
Before the surgical resection of such a mass, the principal decisions to be made from the clinicians are the execution of a preliminary embolization of the tumor and the surgical access to the lesion. There is no global consensus on the necessity of a preliminary embolization6,8,15, especially in low-staging masses, but this procedure may lead to a reduction in the bleeding of the mass during the resection, ensuring a cleaner surgical field and so an easier removal of the mass. 
In this protocol for the managing of ELST, preoperative embolization is always proposed, even for limited and low-staging masses, since it leads to reduced surgery time, reduced blood loss, easier surgery and therefore, reduced morbidity. 
The early diagnosis, based on an accurate and prompt clinical assessment and imaging study in patients reporting Meniere-like symptoms, can guarantee an early-stage surgery in case of an ELST. Further, thanks to a low staging of disease at the diagnosis, an accurate embolization and a precise surgical resection of the mass, it is usually possible to achieve good oncologic results, without disease recurrence and long disease-free survival period, avoiding or reducing the incidence of the main complications of major petrous bone surgery, such as the facial nerve palsy or the postoperative CSF leaks. 
In the presence of an ELST, the imaging assessment, which should include an MRI and an HRCT study, make it possible to stage the tumor. According to the stage of the tumor and the audiologic assessment of the patient, it is possible to define a surgical approach and estimate a prognosis15. 
To date, in fact, surgical resection is considered the treatment of choice in patients with an ELST. Another therapeutic option is the radiation therapy8,15. However, since the role of adjuvant radiation therapy is not well reported yet8,16, it should be considered for patients with residual disease after surgical resection, or in inoperable patients due to morbidity or the excessive tumor extension8,10,15.
As reported by Nelson and colleagues15, another therapy for inoperable patients could be represented by pazopanib, a multikinase inhibitor and antiangiogenic agent. Anyway, there is no evidence currently supporting the use of this drug as primary or adjuvant therapy for ELSTs.
Before the surgical resection, clinicians can propose a preliminary embolization of the mass. Even if recommended by some authors6,8, especially in situations where vascularity of the tumor could otherwise preclude a complete resection, ELST preoperative embolization is not constantly reported in literature13. Even for small masses, in accordance with other authors (e.g., Wu and colleagues6), an accurate preoperative embolization is always ruled out in our center, since it can reduce the difficulty and the morbidity of the surgery, in addition to the risk of severe intraoperative blood loss. In fact, since the main goal in the treatment of ELST is full surgical eradication8,15, small masses must be treated with reduced bleeding as one of the key points in managing this pathology. 
As reported, a low-staging mass with controlled bleeding can be removed through an exclusive posterior labyrinthectomy approach, guaranteeing little postsurgical morbidity and good oncologic results. After the surgical removal of the mass, clinicians must initially deal with the postoperative symptoms and monitor the patient for complications. The eventual specific complications of such a major surgery on the petrous bone include CSF leakages and facial nerve palsy.
According to the literature, postsurgical complications, as far as residual disease after resection are, comprehensibly, more frequent when the tumors are extensive and their resection requires a highly invasive surgery6,8,15. In the case described herein, no major postsurgical complications, as well as no residual disease, were reported. Further, after the histologic confirmation of an ELST, patients with such a tumor should exclude the coexistence of a VHL through specific genetic studies. Genetic studies excluded VHL for the patient herein discussed. 
In a recent systematic review by Tang and colleagues8, from the analysis of a total of 253 unique tumors in 247 patients, reported recurrence or progression after surgery was 21.8%, after a mean time of 46.7 months (from 3 to 180 months) and the disease-free survival was 47.6 &plusmn; 46.4 months in patients with sporadic disease and 49.8 &plusmn; 48.3 months in patients with VHL-associated disease.
Even if there is no consensus on the follow-up of the patients after the resection of an ELST, an MRI study every 6 to 8 months could effectively identify a recurrence or a progression of the disease after surgery. It is not clear how long the MRI follow-up should be. In their systematic review, Tang and colleagues reported a recurrence even after 15 years from surgery, while Poletti et al.10 and Sykopetrites15 reported cases with recurrence after more than 10 years. Thus, a very lasting and accurate protocol of follow up should be considered based on the possibility of a recurrence of the disease after such a long period.
In conclusion, the case reported herein demonstrates the importance of managing ELST through early diagnosis based on an accurate clinical and radiological assessment. Further, an eventual preventive embolization of the mass and an accurate surgery on a small, low-grade tumor, can lead to good oncologic results with limited postoperative surgical morbidity. Despite this, a long-lasting MRI follow up should be always advised, since recurrence of the disease is possible even after a long time after surgery.

Endolymphatic sac tumors (ELST) are neoplasms originating from the endolymphatic sac, a neuroectoderm-derived organ located in the posteromedial surface of the temporal bone. Histologically, ELST are characterizable as low-grade papillary adenocarcinoma1. Usually, ELST are slow-growing, with local aggressiveness and a low risk of distant metastases2,3,4. ELST can be sporadic, but they are also frequently associated with von Hippel Lindau disease (VHL)4.
Given the slow growing rate, the paucity of the clinical signs, and the late onset of the symptoms, they are difficult to diagnose in the early stages, especially when not associated with VHL5,6. The typical symptomatology at diagnosis of ELST includes hearing loss (79.8%), tinnitus (52.6%), and disequilibrium (45.5%), due to endolymphatic hydrops or intralabyrinthine hemorrhages4,7,8. Further and less frequent symptoms are facial palsy (25.6%), headache (13.8%), otalgia (5.1%), and trigeminal symptoms (3.2%)8.
The current treatment of ELST is primarily surgical resection. The tumor&#39;s residuals can be treated with stereotactic radiosurgery, which can be considered if the patient cannot tolerate the operation9,10. The surgical approach and the prognosis are mostly related to the tumor extension6. Even if there is no official staging system for ELST11,12, a recent grading system proposed by Li and colleagues13, based on imaging data and intraoperative findings, defined four main grades, according to the tumor extension. This and other previously proposed staging systems are reported in Table 1.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Article</td>
			<td colspan="4">ELST Staging / Grading</td>
		</tr>
		<tr>
			<td>Bambakidis et al.11</td>
			<td colspan="4">Stage I: confiled to the temporal bone and middle ear</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Stage II: extended to the posterior fossa</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Stage III: extended to the middle cranial fossa</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Stage IV: extended to the clivus and/or sphenoid wing</td>
		</tr>
		<tr>
			<td>Schipper et al.12</td>
			<td colspan="4">Type A: limited to the dura of the posterior cranial fossa</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Type B: infiltration of lateral semicircular canal and/or cochlea</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Type C: infiltration of sigmoid sinus and/or jugular bulb</td>
		</tr>
		<tr>
			<td>Li et al.13</td>
			<td colspan="4">Grade I: confined to the posterior petrous bone between posterior semicircular canal and posterior fossa, may involve facial nerve, no inner ear and jugular foramen invasion</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Grade II: extended anteriorly with invasion of semicircular canals, cochlea, IAC, middle ear, without cerebellopotine angle and jugular foramen involvement</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Grade IIIa: involvement of jugular foramen or internal carotid artery or clivus</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Grade IIIb: extensive intracranial invasion or involvement of cavernous sinus or jugular foramen</td>
		</tr>
		<tr>
			<td>Wu et al.6</td>
			<td colspan="4">Type I: confined to the endolymphatic sac region</td>
		</tr>
		<tr>
			<td></td>
			<td colspan="4">Type II: extended to at least another one anatomic structure</td>
		</tr>
	</tbody>
</table>
Table 1: Previously published tumor staging systems. An overview of previously published grading/staging systems.
To date, only ~300 cases were reported, mostly as single clinical cases or small case series5,6. Recurrence rates and survival estimates have not been clearly defined yet8. In the present paper, we report the clinical and surgical management of a single case of sporadic ELST, as well as the follow-up results, providing clinicians our experience of the handling of such a challenging otologic skull base surgery and rare disease. Here, we describe ELST in a 55-year-old woman who accessed our otologic tertiary level referral center from a peripheric hospital. The patient had been hospitalized 3 days before for a sudden worsening of the left hearing loss, which began 3 months earlier, accompanied by an episode of acute vertigo with nausea and vomiting. The anamnesis was positive for hypertension and hypercholesterolemia, both under treatment, and smoking (3 pack-years). No personal or familiar history of VHL disease or compatible symptoms were reported by the patient.

<table><tbody><tr><td>AC40</td><td>Interacoustic</td><td></td><td>Clinical audiometer</td></tr><tr><td>AT235</td><td>Interacoustic</td><td></td><td>Clinical tympanometry</td></tr><tr><td>Innova 3131</td><td>GE Healthcare</td><td></td><td>Biplane angiograph</td></tr><tr><td>LightSpeed VCT</td><td>GE Healthcare</td><td></td><td>64 Slice CT system</td></tr><tr><td>S2 &amp;pi;Drive</td><td>Striker</td><td></td><td>Drilling system for Otosurgery</td></tr><tr><td>Signa HDX</td><td>GE Healthcare</td><td></td><td>1.5 T MRI system</td></tr><tr><td>SYNAPSYS VNG</td><td>Inventis</td><td></td><td>Video nystagmograph</td></tr></tbody></table>

surgical treatment of an endolymphatic sac tumor

Endolymphatic sac tumors (ELST) are low-grade papillary adenocarcinoma originating from the endolymphatic sac. Usually slow-growing, with local aggressiveness and a low risk of distant metastases, ELST can be sporadic but also frequently associated with von Hippel Lindau disease. The current treatment of ELST is primarily surgical resection. A 55-year-old woman accessed our otologic tertiary level referral center for a sudden worsening of hearing loss in her left ear and vertigo. A magnetic resonance (MRI) and computer tomography scan study subsequently showed a mass in the petrous bone; hence, the presence of an ELST was hypothesized. After embolization of the mass, the patient underwent surgical removal of the lesion. The resection of the mass was done through a translabirinthine approach, with an uneventful procedure. No residual disease remained after surgery. After 24 months of radiologic follow up with MRI, there are no signs of recurrence disease. This paper reports the management of this sporadic ELST, as well as the follow up results, providing clinicians this protocol for the handling of such a challenging otologic skull base surgery and rare disease.

From the audiologic assessment, it was possible to identify a moderately severe left sensorineural hearing loss (Figure 1), with a reduction of word discrimination. The tympanometry was bilaterally normal, and the stapedial reflexes were evocable with ipsilateral and contralateral stimulus. At the videonystagmography , it was possible to assess a grade II horizontal spontaneous nystagmus beating on the right side, which grew in intensity after head shaking. From the clinical and audiological assessment, the case seemed to be associated with a peripheric cochlear and labyrinthic deficit, without signs of central pathology.
Form the MRI study it was possible to identify an occupation of the left mastoid cells by high-intensity mucous material, conditioning a swollen appearance of the cortex bone in the posterior side of the petrous part with obliteration of the ipsilateral pontocerebellar cistern and minimal imprint on the left cerebellar gyri, which was compatible with the presence of an ELST (Figure 2).
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65079/65079fig02.jpg" /> 
Figure 2: Preoperative MRI. T1-weighted SPGR sequence after gadolinium contrast agent administration showed an isointense mass with foci of hyperintensity, with heterogeneous enhancement. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65079/65079fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The patient was then submitted to a high-resolution computer tomography (HRCT) of the petrous bone, with a 64-slice scan that confirmed the presence of an isodense mass on the posterior wall of the petrous bone with erosion and an infiltrative &#34;moth-eaten&#34; pattern (Figure 3).
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/65079/65079fig03.jpg" /> 
Figure 3: Preoperative HRCT. Isodense mass on the posterior wall of the left petrous bone with erosion of petrous bone and an infiltrative &#34;moth-eaten&#34; pattern. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65079/65079fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
According to the Li grading system13, in this case, it was possible to suspect the presence of a grade 2 ELST. The diagnostic digital subtraction angiogram showed a vascular tumor with tumor blush due to blood supply from the ascending pharyngeal, posterior auricular, and occipital branches of the left external carotid artery (Figure 4A).
Post embolization angiogram showed complete obliteration of the tumor blush (Figure 4B). There was no complication during and after the procedure.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/65079/65079fig04.jpg" /> 
Figure 4: Left external carotid artery angiogram lateral view. (A) Tumor blush, (B) complete obliteration of the tumor blush after embolization. Abbreviation: ECA = external carotid artery. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65079/65079fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
After the complete exposure of the dura of the middle and posterior cranial fossa, in the endolymphatic sac area, an easily bleeding neoplasm was identified. The neoplasm was indivisible from the dura of the posterior cranial fossa, so the dura was cut and removed en-bloc with the tumor.
The neoplasm had reached and invaded the IAC, which had to be opened to completely remove the tumor. The intraoperative extemporaneous histological examination indicated the neoplasm as a papillary tumor. Inside the IAC, the facial nerve seemed to be intact, and it was possible to electrically stimulate it, with good muscular responses. There was no appearance of post-surgical cerebrospinal fluid (CSF) leak, and the blood loss due surgery was minimal.
Post surgery, the patient experienced self-limiting vertigo for a week, a total loss of the left residual hearing, but no other complications. In particular, the patient did not present CSF leakages or any grade of facial nerve palsy. One week after the surgery, the definitive histological examination confirmed the papillary nature of the tumor, confirming the diagnosis of ELST. The genetic study excluded the presence of a VHL disease. The patient is in good health. She undergoes radiological follow-up with MRI every 6 to 8 months. After 24 months, she does not present radiological or clinical signs of recurrence disease.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65079/65079fig01.jpg" /> 
Figure 1: Tonal audiometry. Left sensorineural moderately severe hearing loss. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65079/65079fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Surgical Treatment of an Endolymphatic Sac Tumor at JoVE.com

Surgical Treatment of an Endolymphatic Sac Tumor

Here, we discuss clinical and radiological features of endolymphatic sac tumors and report the methodology and results of a surgical removal in a case in care at our otologic referral center.

Endolymphatic sac tumors (ELST) are low-grade papillary adenocarcinoma originating from the endolymphatic sac. Usually slow-growing, with local ...

surgical-treatment-of-an-endolymphatic-sac-tumor

Nanyang Technological University

Research

JoVE Journal

Medicine

537 Views.  University of Pisa. Here, we discuss clinical and radiological features of endolymphatic sac tumors and report the methodology and results of a surgical removal in a case in care at our otologic referral center. 

Video: Surgical Treatment of an Endolymphatic Sac Tumor

Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal model of the condition and an important correlate for human Meniere's disease. In 1965, Robert Kimura and Harold Schuknecht first described an intradural approach for obstruction of the endolymphatic duct (Kimura 1965). Although effective, this technique, which requires penetration of the brain's protective covering, incurred an undesirable level of morbidity and mortality in the animal subjects. Consequently, Andrews and Bohmer developed an extradural approach, which predictably produces fewer of the complications associated with central nervous system (CNS) penetration.(Andrews and Bohmer 1989) 
The extradural approach described here first requires a midline incision in the region of the occiput to expose the underlying muscular layer. We operate only on the right side. After appropriate retraction of the overlying tissue, a horizontal incision is made into the musculature of the right occiput to expose the right temporo-occipital suture line. The bone immediately inferio-lateral the suture line (Fig 1) is then drilled with an otologic drill until the sigmoid sinus becomes visible. Medial retraction of the sigmoid sinus reveals the operculum of the endolymphatic duct, which houses the endolymphatic sac. Drilling medial to the operculum into the area of the endolymphatic sac reveals the endolymphatic duct, which is then packed with bone wax to produce obstruction and ultimately ELH. 
In the following weeks, the animal will demonstrate the progressive, fluctuating hearing loss and histologic evidence of ELH.

This video shows how to surgically obstruct the guinea pig's endolymphatic duct to produce endolymphatic hydrops.

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal ...

Biology

A Revised Surgical Approach to Induce Endolymphatic Hydrops in the Guinea Pig

Endolymphatic hydrops is an enlargement of scala media that is most often associated with Meniere&#39;s disease, though the pathophysiologic mechanism(s) remain unclear. In order to adequately study the attributes of endolymphatic hydrops, such as the origins of low-frequency hearing loss, a reliable model is needed. The guinea pig is a&#160;good model because it hears in the low-frequency regions that are putatively affected by endolymphatic hydrops. Previous research has demonstrated that endolymphatic hydrops can be induced surgically via intradural or extradural approaches that involve drilling on the endolymphatic duct and sac. However, whether it was possible to create an endolymphatic hydrops model using an extradural approach that avoided dangerous drilling on the endolymphatic duct and sac was unknown. The objective of this study was to demonstrate a revised extradural approach to induce experimental endolymphatic hydrops at 30 days post-operatively by obliterating the endolymphatic sac and injuring the endolymphatic duct with a fine pick. The sample size consisted of seven guinea pigs. Functional measurements of hearing were made and temporal bones were subsequently harvested for histologic analysis. The approach had a success rate of 86% in achieving endolymphatic hydrops. The risk of cerebrospinal fluid leak was minimal. No perioperative deaths or injuries to the posterior semicircular canal occurred in the sample. The presented method demonstrates a safe and reliable way to induce endolymphatic hydrops at a relatively quick time point of 30 days. The clinical implications are that the presented method provides a reliable model to further explore the origins of low-frequency hearing loss that can be associated endolymphatic hydrops.

This article demonstrates an extradural approach to obliterate the guinea pig endolymphatic sac and injure the endolymphatic duct with a fine pick in order to induce experimental endolymphatic hydrops.

Endolymphatic hydrops is an enlargement of scala media that is most often associated with Meniere&#39;s disease, though the pathophysiologic mechanism(s) ...

Neuroscience

An Endoscopic Transcanal Transpromontorial Approach for Vestibular Schwannomas using a Computer-Based Three-Dimensional Imaging System

A 2D monocular endoscope has been used in transcanal transpromontory vestibular schwannoma surgery instead of craniotomy. However, the absence of depth perception is the limitation of this approach. With the loss of depth perception, the surgeon will be not able to perform delicate and particularly complicated surgery. A binocular endoscope has been developed to provide stereoscopic vision with better depth perception for complicated anatomic structures and has been applied in some endoscopic surgeries. However, the diameter of the endoscope is a limitation in the performance of transcanal otologic surgeries. A small diameter endoscope facilitates easier surgery in a restricted space. A computer-based 3D imaging system can obtain 3D images in real-time using a small monocular endoscope. In this study, to evaluate the feasibility of a computer-based 3D imaging system for endoscopic lateral skull base surgery, we applied this 3D imaging system in a transcanal transpromontorial approach in two patients with vestibular schwannomas. The surgical procedure was completed without complication in these two cases. There was no mortality, perioperative complications, nor notable postoperative complications. Using this computer-based 3D imaging system, a better depth perception and stereoscopic vision was observed compared to a conventional 2D endoscope. The improvement in depth perception offers superior management of the complicated surgical anatomy.

Here, we present a transcanal transpromontorial approach for vestibular schwannomas using a computer-based three-dimensional (3D) imaging system combined with a two-dimensional (2D) endoscope. This system provided stereoscopic vision, better depth perception and reduced visual fatigue. This 3D imaging system enabled the application of 3D vision technology in endoscopic lateral skull base surgery.

A 2D monocular endoscope has been used in transcanal transpromontory vestibular schwannoma surgery instead of craniotomy. However, the absence of depth ...

Endaural Endoscopic Atticoantrotomy (Retrograde Mastoidectomy) using a Constant Suction Bone-drilling Technique

Endoscopic middle ear surgery is a widely employed minimally invasive surgical technique to address middle ear and mastoid pathology. Bone drilling is the main technical challenge of endoscopic middle ear surgery. The accompanying video describes the detailed protocol of a constant-suction bone-drilling technique and the procedure of endaural exclusive endoscopic atticoantrotomy (retrograde mastoidectomy) using this technique. The main components of this bone-drilling technique include a soft and flexible suction tube, which is placed into the tympanic cavity to provide constant suction, and a soft sleeve, which is wrapped around the drill shaft to prevent the high-speed rotating shaft from damaging the lens of the endoscope. With these simple modifications, the traditional otological electrodrill can be used for drilling a tiny endaural incision in endoscopic middle ear surgery. Based on this bone-drilling technique, endaural endoscopic atticoantrotomy (retrograde mastoidectomy) can be successfully established for the removal of various amounts of bone, depending on the extent of the lesion. The short-term postoperative outcome seems promising.

Endaural Endoscopic Atticoantrotomy Retrograde Mastoidectomy using a Constant Suction Bone-drilling Technique

In this paper, we present the protocol and short-term outcomes of endaural exclusive endoscopic atticoantrotomy using a constant suction bone-drilling technique.

Endoscopic middle ear surgery is a widely employed minimally invasive surgical technique to address middle ear and mastoid pathology. Bone drilling is the ...

An Integrated (Microscopic/Endoscopic) Dissection Ear Surgery Course

Traditionally, otologic surgical training consisted of microscopic cadaveric dissections. However, during the last decades the endoscope has significantly changed the surgical perspective in the otologic field. Thus, the modern ear and lateral skull base surgeon should master the entire spectrum of endoscopic and microscopic approaches, with the aim of tailoring the procedure and guaranteeing the best possible functional outcome. This work proposes a step-by-step guided and illustrated dissection course, including indications for the setup of the cadaver lab and the integration of the microscope and endoscope to enhance the use of both instruments. The alternation of the endoscope and microscope allows the novice to train the correct handling of the instruments in the surgical field under both optical views. This aspect is of utmost importance since it is not advisable to start off a technique without practicing the other one, as both are important and complementary in the modern otologic surgery setting.

An Integrated Microscopic/Endoscopic Dissection Ear Surgery Course

Traditionally, otologic surgical training consisted of microscopic cadaveric dissections. However, during the last decades the endoscope has significantly ...

The Microscopic Transcanal Approach in Stapes Surgery Revisited

The microscopic transcanal (aka transmeatal) surgical approach was first described in the 60s, offering a minimally invasive means of reaching the external auditory canal, the middle ear, and epitympanon. Such an approach avoids a retroauricular or endaural skin incision; however, working through a narrow space needs angled microsurgical instruments and specific training in otologic surgery. The transcanal approach restricts the working space; however, it offers a binocular microscopic vision into the middle ear without extended skin incisions and thus, reducing post-operative pain and bleeding. In addition, this minimally invasive approach avoids scar tissue complications, hypoesthesia of the auricle, and potential protrusion of the pinna. Despite its numerous advantages, this method is still not routinely performed by otologic surgeons. Since this minimally invasive technique is more challenging, there is a need for extensive training in order for it to be widely adopted by otologic surgeons. This article provides step-by-step surgical instructions for stapes surgery and reports possible indications, pitfalls, and limitations using this microscopic transcanal technique.

This article describes the microscopic transcanal technique for stapes surgery, providing step-by-step surgical instructions for familiarizing surgeons with this approach.

The microscopic transcanal (aka transmeatal) surgical approach was first described in the 60s, offering a minimally invasive means of reaching the ...

Endoscopic Cholesteatoma Surgery

Implementation of endoscopes in cholesteatoma surgery resulted in considerable changes in the management of cholesteatoma in the last two decades. Compared to the microscopic approach with an excellent but straight-line view and limited illumination, the introduction of endoscopes provides a wide-angled panoramic view. Moreover, angled lenses allow the surgeon to visualize the middle ear and its hidden recesses through a transcanal, minimally-invasive approach. The endoscope enables the surgeon to remove limited cholesteatoma of the middle ear and its recesses using an exclusive endoscopic technique by taking advantage of these benefits. This reduces the rate of residual disease and sparing external incisions and excessive temporal bone drilling as in a transmastoid approach. Since transcanal endoscopic access is mainly a one-handed technique, it implies the need for specific procedures and technical refinements. This article describes a step-by-step guide as a surgical manual for endoscopic removal of epitympanic cholesteatoma. Different techniques for cholesteatoma dissection and bone removal for epitympanectomy, including curettage and powered instruments such as drills and ultrasonic devices with their outcomes, are discussed. This may offer ear surgeons insight into technical refinements and the latest technological developments and open the horizon for different techniques.

The present protocol describes a step-by-step guide for the complete endoscopic removal of epitympanic cholesteatoma with different techniques for cholesteatoma dissection and bone removal for epitympanectomy.

Implementation of endoscopes in cholesteatoma surgery resulted in considerable changes in the management of cholesteatoma in the last two decades. ...

Endolymphatic Duct Blockage as a Surgical Treatment Option for M&#233;ni&#232;re's Disease

Endolymphatic duct blockage is a relatively new treatment option for M&#233;ni&#232;re's disease, aiming to reduce vertigo attacks while sparing hearing and equilibrium. After a regular mastoidectomy, the posterior semicircular canal is identified, and Donaldson's line is determined. This is a line through the horizontal semicircular canal, crossing the posterior semicircular canal. The endolymphatic sac is usually found at this site under the posterior semicircular canal. The bone of the endolymphatic sac and the dura are thinned until the sac is skeletonized, after which the endolymphatic duct is identified. The duct is then blocked with a titanium clip. Using a computerized tomography (CT) scan, the position is confirmed. Follow-up visits take place 1 week, 6 weeks and 1 year after surgery. To this day, only one prospective trial assessing this method has been conducted, comparing this new method to endolymphatic sac decompression. Results of the duct blockage are promising, with 96.5% of the patients free of vertigo after 2 years. However, further research is required.

Endolymphatic duct blockage is a relatively new surgical method for patients suffering from M&#233;ni&#232;re's disease. Following a regular mastoidectomy, the endolymphatic duct is identified and ligated using a regular titanium hemoclip. The effectiveness of this procedure is currently being assessed in a randomized trial.

Endolymphatic duct blockage is a relatively new treatment option for M&#233;ni&#232;re's disease, aiming to reduce vertigo attacks while sparing hearing ...

Robot-Assisted Transcanal Endoscopic Ear Surgery for Congenital Cholesteatoma

Congenital cholesteatoma accounts for 25% of cholesteatoma cases in children. Transcanal Endoscopic Ear Surgery (TEES) is ideal for these patients because it offers a wide endoscopic view of the middle ear and a minimally invasive approach. The two main limitations are the loss of one operative hand and a narrow external auditory canal in younger children. Here, we present the case of a 3-year-old patient with a Potsic stage III congenital cholesteatoma adherent to the incus and branches of the stapes. A robotic-assisted TEES procedure was performed, during which a robotic arm with 6 degrees of freedom held a 0&#176;, 2.9 mm wide endoscope, enabling the surgeon to work in a narrow environment with both hands. The procedure's duration was 2 h and 9 min, including 16 min for the installation and draping of the robotic arm. After a trans-canal approach, the cholesteatoma was dissected from the ossicles using both a needle (or sickle knife) and suction to stabilize the ossicles and limit the risk of hearing trauma. The cholesteatoma was debulked to reduce its size, allowing it to be pushed under the malleus anteriorly and then separated from other adherences before removal. A tragal cartilage graft was used to reinforce the tympanic membrane.

This protocol describes the removal of congenital cholesteatoma using minimally invasive transcanal endoscopic ear surgery with a two-handed approach and a robotic endoscope holder.

Congenital cholesteatoma accounts for 25% of cholesteatoma cases in children. Transcanal Endoscopic Ear Surgery (TEES) is ideal for these patients because ...

Dissection of the Endolymphatic Sac from Mice

The study of mutant mouse models of human hearing and balance disorders has unraveled many structural and functional changes which may contribute to the human phenotypes. Although important progress has been done in the understanding of the development and function of the neurosensory epithelia of the cochlea and vestibula, limited knowledge is available regarding the development, cellular composition, molecular pathways and functional characteristics of the endolymphatic sac. This is, in large part, due to the difficulty of visualizing and microdissecting this tissue, which is an epithelium comprised of only one cell layer. The study presented here describes an approach to access and microdissect the endolymphatic sac from the wild-type mouse inner ear at different ages. The result of a similar dissection is shown in a pendrin-deficient mouse model of enlargement of the vestibular aqueduct. A transgenic mouse with a fluorescent endolymphatic sac is presented. This reporter mouse can be used to readily visualize the endolymphatic sac with limited dissection and determine its size. It can also be used as an educational tool to teach how to dissect the endolymphatic sac. These dissection procedures should facilitate further characterization of this understudied part of the inner ear.

This study describes how to dissect the endolymphatic sac from the inner ear of the mouse at different ages. The result of a similar dissection is shown in an Slc26a4-null mouse model of enlargement of the endolymphatic sac. A transgenic mouse with a fluorescent reporter expressed in the endolymphatic sac is presented as a model to readily visualize the endolymphatic sac, and educational tool.

The study of mutant mouse models of human hearing and balance disorders has unraveled many structural and functional changes which may contribute to the ...