Endoscopic endonasal surgery of the midline skull base: anatomical study and clinical considerations

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The midline skull base is an anatomical area that extends from the anterior limit of the cranial fossa down to the anterior border of the foramen magnum. Resection of lesions involving this area requires a variety of innovative skull base approaches. These include anterior, anterolateral, and posterolateral routes, performed either alone or in combination, and resection via these routes often requires extensive neurovascular manipulation. The goals in this study were to define the application of the endoscopic endonasal approach and to become more familiar with the views and skills associated with the technique by using cadaveric specimens.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>To assess the feasibility of the endonasal route for the surgical management of lesions in the midline skull base, five fresh cadaver heads injected with colored latex were dissected using a modified endoscopic endonasal approach.</jats:p> <jats:p>Full access to the skull base and the cisternal space around it is possible with this route. From the crista galli to the spinomedullary junction, with incision of the dura mater, a complete visualization of the carotid and vertebrobasilar arterial systems and of all 12 of the cranial nerves is obtainable.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The major potential advantage of the endoscopic endonasal approach to the skull base is that it provides a direct anatomical route to the lesion without traversing any major neurovascular structures, obviating brain retraction. Many tumors grow in a medial-to-lateral direction, displacing structures laterally as they expand, creating natural corridors for their resection via an anteromedial approach.</jats:p> <jats:p>Potential disadvantages of this procedure include the relatively restricted working space and the danger of an inadequate dural repair with cerebrospinal fluid (CSF) leakage and potential for meningitis resulting. These approaches often require a large opening of the dura mater over the tuberculum sellae and posterior planum sphenoidale, or retroclival space. In addition, they typically involve large intraoperative CSF leaks, which necessitate precise and effective dural closure.</jats:p></jats:sec>

Surgical management of primary central nervous system germ cell tumors

“…This ability has recently been shown to offer a potentially more sensitive appraisal of tumor spread than is available with contrastenhanced MR imaging. 5,30,44 An example of germinoma dissemination noted at the time of endoscopic tumor biopsy is shown in Fig. 2.…”

“…The advent of endoscopic-assisted transnasal surgery offers an appealing alternative to intracranial surgery for tumors situated in the parasellar region. 5,16,34 Using the nasal aperture as a primary surgical corridor, the transsphenoidal route or extended cranial-base routes can be used to resect intradural tumors. Currently there is no dedicated study of transnasal endoscopically assisted surgery for parasellar CNS GCT, but the anatomical considerations do not differ greatly from other tumors that have been successfully managed using this approach.…”

Endoscopic management of a lower clival chondroid chordoma: case report

“…Cavallo et al reported the lateral limitation of the foramen magnum is the anterior third of the occipital condyle, as the hypoglossal canal is located anterior and in the middle third of each condyle (3)(4). Laterally extended lesions must be treated by additional surgical approaches or radiotherapy.…”

Critical Appraisal of Extent of Resection of Clival Lesions Using the Expanded Endoscopic Endonasal Approach

“…Critical neurovascular structures, primarily the paraclival internal carotid artery (ICA) segments and the lower cranial nerves, are generally considered to represent the lateral limits of safe exposure. 19,21,22 Clinically, clival lesions are often found to displace, invaginate around, and extend beyond these structures, thus restricting the success of an EEEA. 23 Understanding the specific anatomic limitations associated with this approach is important to better predict preoperatively whether an expanded endoscopic, lateral, or anterior "open" procedure would be most effective in safely achieving the greatest amount of tumor removal.…”