Endoscopic Assisted Retrosigmoid Approach

The retrosigmoid route represents one of the traditional surgical approaches to the posterior cranial fossa and, in particular, to the cerebellopontine angle. The indications are neoplasms of the poste- rior cranial fossa and/or the cerebellopontine angle, like VIII cranial nerve schwannomas, meningiomas, epidermoid cysts, and metasta- ses, with or without internal auditory canal involvement with/with- out serviceable hearing, symptomatic neurovascular conflicts, or brainstem implant placement. The retrosigmoid approach requires a retromastoid craniotomy (or craniectomy), a microscopic dissection with dural incision behind the sigmoid sinus, in order to expose the cerebellar cisterna and open the arachnoid to enter the subarach- noid space. This maneuver allows cerebrospinal fluid drainage, which is a key step to decompress the anatomical structures inside the cerebellopontine angle and to create enough space to work in this region. At the end of microscopic lesion removal, an angled optics is useful to help the surgeon dissect the pathology and remove the remnants with intrameatal extension inside the fundus of the internal auditory canal. In this way, an extensive drilling of the posterior portion of the internal auditory canal can be avoided. Other important things to consider are the possibility to check the relationship of the pathology with the anatomical structures in the cerebellopontine angle at the beginning of the procedure and the great value of the angled optics (45-degree and 70-degree lenses) during the final check to control the radicality of the excision. Moreover, in case of neurovascular conflict, the endoscope allows the surgeon to directly reach the area. In these cases, the magnifica- tion of the image also provides a better visualization of any possible anomalies of the nerve position, and the final check after the surgical procedure also allows the surgeon to be sure about the correct reso- lution of the conflict and to make an accurate hemostasis.