gms | German Medical Science

ESBS 2005: Skull Base Surgery: An Interdisciplinary Challenge
7th Congress of the European Skull Base Society held in association with
the 13th Congress of the German Society of Skull Base Surgery

18. - 21.05.2005, Fulda, Germany

Tumour staged surgery of endolymphatic sac tumours (ELST)

Meeting Contribution

  • Joerg Schipper - Department of Oto-Rhino-Laryngology, University of Düsseldorf, Düsseldorf, Germany
  • Wolfgang Maier - Department of Oto-Rhino-Laryngology, University of Freiburg, Freiburg, Germany
  • Steffen Rosahl - Department of Neurosurgery, Helios Hospital Erfurt, Erfurt, Germany
  • Marcos Tatagiba - Department of Neurosurgery, University of Tuebingen, Tuebingen, Germany

ESBS 2005: Skull Base Surgery: An Interdisciplinary Challenge. 7th Congress of the European Skull Base Society held in association with the 13th Congress of the German Society of Skull Base Surgery. Fulda, 18.-21.05.2005. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc05esbs39

doi: 10.3205/05esbs39, urn:nbn:de:0183-05esbs396

Published: January 27, 2009

© 2009 Schipper et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.




Endolymphatic sac tumours (ELST) were first described in 1984 [1]. Their histological classification was difficult because their characteristic papillary structures pointed to a papillary adenoma of the middle ear mucosa [2], whereas the aggressive growth behavior with bone and soft tissue infiltration suggested a malignant tumour [3]. Heffner identified the endolymphatic sac as the origin of these tumours and categorized them as low grade adenocarinomas [4]. Since the first description of the ELST 1984 there have been about such 100 cases reported in the literature, and not a single report of metastatic spread [5]. When ELST is diagnosed, one shouldrule out the presence of von Hippel-Lindau (VHL) disease [6]. The endolymphatic sac is formed between a duplication the posterior cranial fossa dura mater. The growth of ELST is characterized by fast intracranial expansion with no restriction by bony borders, with lethal potential by brain compression or meningitis, therefore requiring surgical intervention. Neurosurgical and neurootosurgical approaches have been designed [5]. The neurosurgical procedures are based on approaches that make use of the subarachnoid space of the posterior fossa, whereas the neurootosurgical methods gain access to ELST via the temporal bone. The goal of surgery is complete tumour extirpation, and preservation of the facial nerve and possibly hearing. Since ELST has been acknowledged only during the last years as a tumour entity, no consensual diagnostic and therapeutic guidelines exist up to now. We attempted a first-time classification of ELST based on our own clinical experience and literature data, as well as to develop a treatment strategy adapted to the tumour stage.

Methods and patients

We developed a staging system for ELST under consideration of data available in the literature and our own experience with these tumours. The staging of ELST is based on imaging attributes of the tumour (Table 1 [Tab. 1]). Thus, we define an ELST as type A if the tumour does neither invade the dura nor the bony cortex of the temporal bone, while the functional integrity of the facial and vestibule-cochlear nerves remains preserved. Thin-section, bone-window CT images of the skull base were used for the preoperative planning and exclusion of possible erosions of the temporal bone. As type A ELST is by definition locally limited, it may be resected via a transmastoid approach with the preservation of the facial and vestibulo-cochear nerves. For complete tumour removal, the dura must be also resected within the limits of the Trautmann triangle in order to ensure the complete tumour matrix extirpation. In all these cases, transmastoidal duraplasty is required. In the presence of CT evidence of bony erosion of the otic capsule, the ELST is staged as type B (Table 1 [Tab. 1]). These patients suffer from hearing loss and/or vertigo but the facial nerve is not damaged. The translabyrinthine approach with facial nerve preservation is appropriate in type B. Since the inner ear is eroded or destroyed, the lateral wall of the internal auditory canal is drilled away under preservationof the facial nerve. For a complete removal of the tumour matrix, dural excision and duraplasty is required. The subarachnoidal exposure should be performed by a skilled neurosurgeon. In the ELST-type C the sigmoid sinus and jugular bulb are infiltrated by tumour. The bone around the jugular bulb is altered and the margins of the sigmoid sinus are eroded. On CT, the fallopian canal around the mastoid segment of the facial nerve is eroded and the otic capsule destroyed. Clinically there is complete deafness ipsilaterally to the tumour. The facial nerve may be affected as well. We recommend the infratemporal approach for safe distal and proximal ligation and resection of sigmoid sinus and jugular bulb and complete tumour removal. Transposition of the facial nerve is performed if required by the circumstances (Fisch A infratemporal approach). As considerable loss of blood because of high tumour vascularization is possible in ELST-type C, preoperative embolization should be considered.

Seven patients were referred to the interdisciplinary Skull Base Center of the University of Freiburg, with suspected ELST on MR scans of the head. All patients had normal function of the facial nerve. There were two patients with an ELST-type A, of which one had intact hearing, while the other was deaf on the affected ear. The latter patient had had a previous transmastoid resection of an ELST earlier. Two patients were classified as ELST-type B: one had ipsilateral sensory hearing loss, the other was deaf. Three patients had a type C tumour, of whom two had ipsilateral profound hearing loss. One of the type C tumours was suspected to be a locally recurrent or residual ELST after previous resection.


All patients were surgically treated with curative intent. The staging and surgical approach was based on our ELST staging and treatment standard (Table 1 [Tab. 1]). The anatomic continuity and preoperative functional integrity of the ipsilateral facial nerve was preserved in all these patients after the operation (House-Brackmann grade I). The two type A ELST were removed via the transmastoidal approach under preservation of the anatomic integrity of the vestibulo-cochlear nerve and the preoperative hearing threshold in one of these patients, whereas the other was ipsilaterally deaf preoperatively. The lateral semicircular canal was found opened but uninvolved by tumour, thus the preoperative deafness was a result of iatrogenic violation of the inner ear during the previous operation. One of the type B ELST patients had suffered from vertigo and had preoperative ipsilateral high-tone hearing loss and bad speech recognition. The preoperative CT showed that the tumour had eroded into the perilymphatic space of a semicircular canal. This opening was found intraoperatively to be sealed off by tumour. Another patient with ELST-type B and VHL syndrome was ipsilaterally deaf at the time of his referral. The ELST type B was completely resected through a translabyrinthine approach.

One patient with an extended type C ELST presented to our center with an already advanced infiltration of the entire osseous labyrinth, sigmoid sinus, and jugular bulb. The massive vascular invasion was demonstrated by MRA. The tumour was completely removed via infratemporal and translabyrinthine approach with the ligation of the sigmoid sinus and jugular bulb. Based on the large extent of this ELST and the hypervascularity shown on MRA, we preoperatively embolized branches of the ascending pharyngeal artery and maxillary artery, which were angiographically shown to feed the tumour. Despite embolization, the tumour was very vulnerable and bleeding during surgery. Intraoperative facial nerve integrity monitoring was employed in all cases.

After a follow up period ranging 4–38 months, no recurrence was observed on periodically repeated MRI. A lumbar tap for CSF pressure reduction was left in place in all patients for 3 to 7 days postoperatively. The only postoperative morbidity occurred in one patient who complained of lightheadedness for 2 weeks that spontaneously resolved. No intraoperative and postoperative complications occurred.


The endolymphatic sac is a cavity within the duplication of the posterior cranial fossa which lies in a triangular area of the dura between the sigmoid sinus, the superior petrosal sinus, and the lateral semicircular canal (Trautmann triangle). This area of the dura is very important in ELST because it constitutes the area of original tumour-forming matrix, consequently it has to be resected with the tumour [7]. Considering its position in the immediate vicinity of vital structures of the central nervous system, we prefer the surgical approach to ELST through the temporal bone by mastoidectomy. Duraplasty has to be performed to avoid CSF leakage through the iatrogenic dural defect. Hearing preservation requires that the integrity of the perilympatic space is not violated by opening the semicircular canals intraoperatively. However, for a complete tumour ablation, the dura must be exposed and resected deeply into the vestibular aqueduct to the level of the isthmus of the endolymphatic duct. Alternative surgical methods are known in the neurosurgical literature as the antero- and retrosigmoid, as well as the suboccipital approaches. These techniques have the merit of accessing ELST by hearing-preserving surgical corridors (but this is true equally for to the transmastoidal approach). These approaches, however, address the lesion through a narrow-angle postero-inferior route that offers limited space for endolymphatic duct manipulation, whereby the resection of the tumour matrix in the endolymphatic duct isthmus becomes more difficult and, to our opinion, the risk of residual tumour increases. Furthermore, these neurosurgical approaches do not afford a thorough exploration possibility of the temporal bone when deeply infiltrated by advanced tumours. The neurosurgical approaches are generally accepted as alternative techniques intended only for the resection of type A ELST. We recommend the transmastoidal approach for resection of all 3 types of ELST, owing to the better view of the inner ear structures. The surgical corridor may be extended to a translabyrinthine or infratemporal fossa dissection depending on tumour extent, thus allowing safe tumour resection in the temporal bone. It is controversial if preoperative embolization is effective before surgical intervention in ELST or not. The vascularization of ELST is very inhomogeneous, and it is different from that of paragangliomas which are more readily amenable to successful devascularization. So a complete embolization in ELST is not feasible. We performed preoperative embolization only in one of our patients, and the effect was minor in comparison with that usually achieved in temporal bone paragangliomas. Radiotherapy remains the treatment of choice in inoperable patients. The literature on this subject is very limited. In individual cases and by all means only in advanced variants of type C ELST that show evidence of brain infiltration, radiotherapy should be considered and offered as a therapeutic option. It is our conviction based on this series, despite its limited number of cases, and on the available literature that the treatment of choice of the rare endolymphatic sac tumour is a stage-adapted transmastoidal surgery because of lacking mortality and very low morbidity.


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