This protocol is significant as it shows how to treat an endolymphatic sac tumor effectively. A prompt diagnosis based on the clinical picture and imaging assessment could lead to a manageable surgery for tumor removal. To begin, perform MRI examination using axial fluid-attenuated inversion recovery and axial fast spin echo T2-weighted sequences.
Target steady-state free precession images with a fast imaging employing steady-state acquisition, or FIESTA, sequence on the inner ear. If a mass appears in the context of the petrous bone, perform a high-resolution computer tomography with at least 64-slice scan to confirm the diagnosis. Once the ELST is suspected, define the grading of the tumor and plan the surgical approach for the mass resection.
After performing a coil embolization and resection of the mass, make a C-shaped retroauricular incision, and raise the flap of the temporalis muscle. Perform ample mastoidectomy with a Stryker S2 PiDrive drilling system, and cut the round precision fluted tips and the coarse and fine diamond round tips from the drilled structures. Expose the sigmoid sinus posteriorly and the dura of the middle cranial fossa superiorly.
Complete an ample antrotomy with complete exposure of the small process of the incus. Then prepare a posterior tympanotomy by drilling out all the retrofacial mastoid cells up to the mastoid tip until the jugular bulb is identified. Complete the posterior labyrinthectomy by dissecting the semicircular canals.
Dissect the posterior bony labyrinth until identification of the internal auditory canal. Next, cut the dura and remove it on block with the tumor to identify the neoplasm and completely remove the tumor. Conduct an intraoperative extemporaneous histological examination.
Seal the posterior tympanotomy and the antrotomy with surgical wax, and fill the ample mastoid cavity with autologous abdominal fat and fibrin glue. From the audiologic assessment, it was possible to identify moderately severe left sensory neural hearing loss with reduced word discrimination. The left mastoid cells were occupied by high-intensity mucous material, causing a swollen appearance of the cortex bone and the posterior side of the petrous part with obliteration of the ipsilateral pontocerebellar cistern and minimal imprint on the left cerebellar gyri, consistent with the presence of an ELST.
The high-resolution computer tomography of the petrous bone with a 64-slice scan confirmed the presence of an isodense mass on the posterior wall of the petrous bone with erosion in an infiltrative moth-eaten pattern. According to the Lee grading system, a grade 2 ELST was suspected. The diagnostic digital subtraction angiogram showed a vascular tumor with tumor blush due to blood supply from the left external carotid artery's ascending pharyngeal, posterior auricular, and occipital branches.
The post-embolization angiogram showed complete obliteration of the tumor blush without any complications during and after the procedure. After a prompt diagnosis, a full resection of an endolymphatic sac tumor is doable, even if demanding. During the surgery, the most important point is to perform a very ample mastoidectomy, providing a full exposure of the posterior labyrinth and a good access to the endolymphatic sac region.
