Peer-Review ReportThe Transconjunctival Transorbital Approach: A Keyhole Approach to the Midline Anterior Skull Base
Introduction
Numerous craniofacial approaches have been developed to address the anatomic challenges of approaching the anterior skull base (5, 19, 20, 24, 26). Anatomically, there are multiple osseous compartments (e.g., frontal sinus, the orbits) that can limit direct access to the anterior cranial fossa. These compartments must also be visualized to resect pathology extending into these regions from the anterior cranial fossa. These different approaches (i.e., frontotemporal sphenoidal craniotomy, extended bifrontal craniotomy, transfacial approaches) provide advantages and corridors appropriate for selected lesions (19, 20, 24, 26). Characteristics that influence the type of approach include the malignant potential of the lesion, lesion epicenter, goals of surgery (negative margins, en bloc resection, neural decompression), and involvement of the paranasal sinuses and surrounding compartments.
These traditional craniofacial approaches are associated with risks, and although they are tolerated for the resection of malignant pathology, they may not be considered acceptable for benign pathology (i.e., CSF leaks, meningiomas) or malignant disease with less extensive anatomic involvement. In an effort to minimize these risks for such lesions, minimally invasive approaches, such as endonasal endoscopy and keyhole craniotomies, are now increasingly used (18, 20, 21). Although endonasal approaches have reduced the morbidity of accessing pathology in the nasal cavity, they have limitations in dealing with the anterior skull base, including the inability to perform microsurgical dissection with complex lesions, adequate dural closure, access to the anterior cranial fossa laterally over the orbits away from the midline, and limited working space when multiple surgeons are working (23). Supraorbital craniotomy with an orbital ridge osteotomy has been described through various incisions (supraciliary, transciliary, and transpalpebral) to the anterior cranial fossa, suprasellar region, and interpeduncular cistern (3, 8, 9, 18, 20, 21, 22). However, these approaches are restricted by their anterolateral trajectory to the midline anterior skull base; the angulation of the orbital roof can be variable restricting access to the cribriform plate region.
The transconjunctival incision, first described by Bourguet in 1924 (2) for cosmetic surgery, could provide an alternative, direct route to selected lesions in the anterior cranial fossa, while avoiding risks with traditional craniofacial approaches and circumventing obstacles with currently available keyhole craniotomies. Currently used for intraorbital lesions and orbital fractures (14, 15), an incision made in the conjunctiva could provide not only direct access to the orbital ridge but also a more medially based trajectory to the cribriform plate region and laterally over the orbits. In addition, the transconjunctival approach can be supplemented with endonasal endoscopy to permit improved access to lesions in the anterior cranial fossa also involving the paranasal sinuses. We present our initial experience with the transconjunctival approach in the management of anterior cranial base pathology.
Section snippets
Methods
We describe our technique for transconjunctival medial orbital craniectomy for accessing the anterior cranial fossa. Depending on lesion location, an endonasal approach can be combined with the transconjunctival craniectomy. For the clinical portion of this study, all patients treated via a transconjunctival craniectomy during the period 2009–2011 at The Johns Hopkins Medical Institutions were included in the cohort study. Approval was obtained from The Johns Hopkins Institutional Review Board
Clinical Analysis
Six minicraniotomies via a transconjunctival approach were performed on three male and three female patients ranging in age from 11–62 years (Table 1). Two patients underwent surgery for an oncologic process (juvenile angiofibroma, esthesioneuroblastoma); there was intracranial involvement in both patients and evidence of additional dural disease in the patient with esthesioneuroblastoma. The patient undergoing resection of a juvenile angiofibroma had disease involvement of the pterygomaxillary
Discussion
Recognizing that the approach should match the pathology of the lesion and the goals of surgery, minimally invasive approaches have been developed to minimize morbidity associated with the surgical approach. Interest has increased in minimally invasive approaches (open and endoscopic) to pathology in the anterior cranial fossa. Transorbital approaches as a means for emergency access to the ventricle have been described (25). The concept of the orbit as a natural corridor to the anterior cranial
Conclusions
The concept of “minimally invasive” neurosurgery does not simply refer to the incision or soft tissue dissection performed but ultimately the “collateral damage” created by neural manipulation and vascular sacrifice and whether or not the goals of surgery (i.e., negative margins for a sinonasal malignancy) have been effectively achieved. Ultimately, these considerations are important in deciding whether or not an open or endoscopic surgical approach should be performed and whether or not
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.