Introduction: Vestibular schwannomas are the most frequent group of nervous system tumors, and the most frequent in the posterior fossa, followed by meningiomas. They are benign lesions of slow growth, grade I according to the 2016 WHO classification. The standard approach is retro sigmoid with a microscope, using an endoscope to explore blind spots under the microscope; however, pure endoscopic approaches with good surgical and functional results have been reported. Objective: To present a representative case of pure endoscopic resection of a vestibular schwannoma. Materials and Methods. A 54-year-old woman consulted for right hearing loss, with no other neurological signs, and contrast-enhanced MRI revealed a tumor of the cerebellopontine angle with remodeling of the internal auditory canal. Tumor resection was performed entirely using an endoscopic technique. Results. There were no intraoperative complications. During the post-operatory she presented paresis of the VII cranial nerve House Brackman III. Conclusions. In our case, a pure endoscopic approach allowed us to completely resect the vestibular schwannoma.
Keywords: Endoscopic Surgery; Vestibular Schwannoma; Skull Base
Vestibular schwannomas (VS) represent between 8 and 10% of intracranial tumors, with an average annual incidence of 0.78 to 1.15 cases per 100,000 inhabitants . They are well-differentiated slow-growing tumors that originate from Schwann cells , 95% develop from the VIII cranial nerve, with the V cranial nerve being the second most frequent . According to the WHO-2016 classification, they are grade I .
In recent years, some skull base surgeons have begun to experiment with endoscopic techniques for pathology of the cerebellopontine angle (CPA) . Several reports describe a better visualization of neurovascular structures of the CPA with an endoscope compared to the microscope [3-8]. The intracanalicular extension of the lesions is best eliminated under endoscopic control, trying to avoid extensive drilling of the posterior face of the internal auditory canal . Currently the endoscope is mainly used as a complement in conventional surgeries, to explore blind spots under a microscope. VS surgery provides an very suitable scenario for the use of the endoscope in the posterior fossa . We present a representative case of complete endoscopic resection of VS at the National Institute of Neurological Sciences in Lima, Peru.
Materials and Methods
A 54-year-old woman with no significant medical antecedents consulted for a 2-year history of decreased hearing in the right ear, without any other symptoms. Neurological and neuro-otological evaluation revealed marked hearing loss in the right ear, with no other neurological signs. On magnetic resonance imaging (MRI), an extra-axial lesion in the right CPA can be seen that remodels in the internal auditory canal (IAC), with diameters of 2.5 * 2.7 * 2.3 cm, homogeneously enhancing after gadolinium injection. In the T2-weighted sequence, large right APC cisterns can be seen, which we considered a favorable anatomical detail for the endoscopic approach, making it unnecessary to retract the cerebellar parenchyma to reach the lesion (Figure 1).
Figure 1: Gadolinium enhanced magnetic resonance images in axial, coronal, and sagittal views: extra-axial tumor homogeneously enhancing after contrast, which slightly displaces the pons and right middle cerebellar peduncle. Widened internal auditory canal with part of the tumor inside and large cerebellopontine angle cisterns.
Patient with Mayfield head in left ¾ lateral position. A standard retrosigmoid craniotomy of approximately 3 cm in diameter was performed. 0°, 4mm and 18 cm optics were used, and a fourhanded approach was performed. After the durotomy based on the sigmoid sinus, the optics entered at the level of the union of the transverse and sigmoid sinuses. Cerebrospinal fluid was drained to widen the approach space and thus avoid retracting the cerebellum (Figure 2, 3). The tumor and its medial, lateral, cephalic and caudal margins were defined, identifying and protecting the VII-VIII cranial nerve complex that was observed in the posterior-inferior margin of the tumor. The tumor was resected using the instruments for endonasal surgery, straight instruments, initially as internal decompression to finally resect the capsule. Since the main difficulty of this surgical technique is the limited maneuverability in such a small space, the straight endonasal surgeries instruments, in our opinion, favor maneuverability in this reduced space. The tumor was a soft, poorly vascularized, yellowish-colored tumor typical of VS. There were no complications during surgery, achieving total resection of the tumor.