Normal hearing after resection of a large vestibular schwannoma

Abstract

Advances in anesthesia and surgical techniques have brought the surgical mortality rate for vestibular schwannomas (VS) to less than 1% [1][2][3] . Increased preservation rates of facial and cochlear function were observed in the most recent large series by Samii et al.1 . Nevertheless, preservation of House-Brackmann grade I and Hannover Class H1 (PTA <20dB and SDS >95%) hearing function postoperatively after total removal of large tumors is still a challenge, even in experienced hands 1,2,[4][5][6] . Our objective is to add to the literature a case of a large VS that was totally excised, with preservation of normal facial and hearing functions. Details on the surgical technique are presented. CASE Case descriptionA 30-year-old female presented with a 2-month history of trigeminal neuralgia in the right V3 distribution, along with normal hearing, an unusual symptomatology for a large VS. Neurological examination was normal. Imaging studies showed a large (34 × 33 × 28 mm), enhancing, spherical mass in the right cerebellopontine angle with erosion of the porus acusticus but no dural tail. A vestibular schwannoma, extension Class T4b (IV ventricle was compressed and distorted), was diagnosed (Fig 1). Her audiometry showed Class H1 hearing in the right ear. Surgical techniqueA three-quarter prone position was used, with the nose pointing up 10 degrees and vertex tilted 15 degrees down, relative to the operating room floor. A lumbar drain was used to drain 50 cc mL CSF throughout the opening. A standard suboccipital retrosigmoid approach was used and the cerebellum was gently retracted after opening the Cisterna Magna. The bed was totally rotated away so the surgeon could have a tangential view of the internal auditory canal (IAC). The configuration of the lesion allowed drilling the posterior lip of the porus, which was followed by internal debulking of the tumor using microinstruments. The intrameatal portion of the facial nerve was then identified at the fundus with the aid of a monopolar stimulator. We used facial nerve monitoring throughout but no cochlear nerve monitoring was done. Although we did not expect preservation of hearing, all attempts were made to preserve the cochlear nerve intact. The cochlear and facial nerves were preserved anatomically with a glistening layer of arachnoid overlying their posterior surface, to avoid any stretching on them. Facial nerve function was confirmed at the end of the case by stimulation at the brainstem using a 0.1 mA current. Total removal was confirmed after inspection of the tumor bed. Hemostasis was carefully done. The meatus was covered with a free muscle graft and biological glue. A cranioplasty was performed using polymethylmethacrylate after a watertight dural

Automated facial–vestibulocochlear nerve complex identification based on data‐driven tractography clustering

“…We used multishell HCP data to create the template, which is of high quality with minimal distortion artifacts and a small voxel size of 1.25 Â 1.25 Â 1.25 mm. 3 Second, we found that deterministic tractography is more suitable than probabilistic tractography in creating the FVN template. In this study, we mainly forced on the cisternal portion of the FVN and the portion just entering the brainstem that does not have a large bend.…”

“…1 The FVN controls facial expression 2 and hearing. 3 Tumor 4 and intraoperative inadvertent injury may lead to FVN dysfunctions, such as paralysis, impaired facial function, 5 and hearing loss, 6 or psychological issues. 7 The aim of surgical treatment is to excise tumors totally while preserving FVN function.…”

“…The facial–vestibulocochlear nerve complex (FVN) consists of cranial nerves (CNs) VII and VIII, which emerge from the lower lateral pons across the cisternal portion and enter the internal auditory canal (IAC) 1 . The FVN controls facial expression 2 and hearing 3 . Tumor 4 and intraoperative inadvertent injury may lead to FVN dysfunctions, such as paralysis, impaired facial function, 5 and hearing loss, 6 or psychological issues 7 .…”