2026 Poster Presentations
P116: ENDOLYMPHATIC SAC TUMOR MASQUERADING AS A VESTIBULAR SCHWANNOMA
Douglas J Totten, MD, MBA; Hunter L Elms, MD; Rick F Nelson, MD, PhD; Indiana University
Introduction: Endolymphatic sac tumors (ELST) are rare, locally aggressive tumors of the posterior petrous ridge which likely originate from the endolymphatic sac epithelium. ELSTs may originate de novo or may be associated with von Hippel-Lindau (VHL) disease. This report discusses the case of a sporadic ELST masquerading as a vestibular schwannoma (VS).
Methods: Case report of a patient with a large ELST initially diagnosed as a VS or paraganglioma.
Results: A 42-year-old patient presented with a known, progressive, left jugular foramen tumor, a 5-year history of progressive hearing loss, and a 2-year history of progressive facial palsy to House-Brackmann (HB) III/VI, and new-onset dysequilibrium. The patient presented due to facial weakness after prior loss to follow-up at an outside institution. 5-year interval MRI identified an enlarged 2.6 x 1.7 x 2.8 cm cystic-solid mass with multiple high velocity internal flow voids, avid contrast enhancement, significant T2 signal, and no restricted diffusion. Differential considerations included cystic schwannoma and paraganglioma (Figure 1). CT demonstrated lytic change throughout the labyrinth, cochlea, internal auditory canal, and middle ear (Figure 2). The patient subsequently underwent excision of the mass via a translabyrinthine/transcochlear approach. As the tumor extended into the labyrinthine segment and IAC, meticulous exposure of the entire course of the facial nerve was necessary for complete tumor removal. Postoperatively, the patient experienced transient dizziness and had a seroma managed with bedside aspiration. Facial function was stable at HB III/VI. Final pathology demonstrated an ELST. Postoperative imaging at 1 month (Figure 3) was consistent with complete tumor removal and the patient will be serially monitored.
Conclusion: ELSTs can present with symptoms and imaging findings similar to other temporal bone pathologies, like vestibular schwannomas or jugular paragangliomas. Although rare, ELSTs should be considered as a possible diagnosis, particularly when imaging findings are not classic for VS or paraganglioma. The mainstay for ELST treatment is surgical resection with gross total resection, when possible, with great care taken to preserve facial nerve function.
Figure 1. Pre-operative magnetic resonance imaging (MRI) of the endolymphatic sac tumor with characteristics suggestive, but not diagnostic, for schwannoma and paraganglioma. A) Axial T2-weighted image of tumor; B) Coronal T2-weighted image; C) Axial T1-weighted non-contrast image of tumor; D) Coronal post-contrast T1-weighted image demonstrating components with avid enhancement.
Figure 2. Pre-operative computed tomography (CT) axial imaging demonstrating erosion of the labyrinthine canals, cochlea, internal auditory canal, and middle ear structures. A) Axial image demonstrating normal (right) and diseased (left) temporal bone structures; B) Coronal image demonstrating normal bony covering of inner ear structures; C) Coronal image demonstrating extent of erosion from the endolymphatic sac tumor.
Figure 3. 1-month postoperative magnetic resonance imaging (MRI) of the right temporal bone demonstrating complete removal of endolymphatic sac tumor (ELST). A) Axial T2-weighted image; B) Coronal T2-weighted image; C) Axial T1-weighted post-contrast image; D) Coronal T1-weighted post-contrast image.