Defining the lateral limits of the endoscopic endonasal transtuberculum transplanum approach: anatomical study with pertinent quantitative analysis

Abstract

OBJECTIVE The extended endoscopic endonasal transtuberculum transplanum approach is currently used for the surgical treatment of selected midline anterior skull base lesions. Nevertheless, the possibility of accessing the lateral aspects of the planum sphenoidale could represent a limitation for such an approach. To the authors' knowledge, a clear definition of the eventual anatomical boundaries has not been delineated. Hence, the present study aimed to detail and quantify the maximum amount of bone removal over the planum sphenoidale required via the endonasal pathway to achieve the most lateral extension of such a corridor and to evaluate the relative surgical freedom. METHODS Six human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy of the University of Barcelona. The laboratory rehearsals were run as follows: 1) preliminary predissection CT scans, 2) the endoscopic endonasal transtuberculum transplanum approach (lateral limit: medial optocarotid recess) followed by postdissection CT scans, 3) maximum lateral extension of the transtuberculum transplanum approach followed by postdissection CT scans, and 4) bone removal and surgical freedom analysis (a nonpaired Student t-test). A conventional subfrontal bilateral approach was used to evaluate, from above, the bone removal from the planum sphenoidale and the lateral limit of the endonasal route. RESULTS The endoscopic endonasal transtuberculum transplanum approach was extended at its maximum lateral aspect in the lateral portion of the anterior skull base, removing the bone above the optic prominence, that is, the medial portion of the lesser sphenoid wing, including the anterior clinoid process. As expected, a greater bone removal volume was obtained compared with the approach when bone removal is limited to the medial optocarotid recess (average 533.45 vs 296.07 mm; p < 0.01). The anteroposterior diameter was an average of 8.1 vs 15.78 mm, and the laterolateral diameter was an average of 18.77 vs 44.54 mm (p < 0.01). The neurovascular contents of this area were exposed up to the insular segment of the middle cerebral artery. The surgical freedom analysis revealed a possible increased lateral maneuverability of instruments inserted in the contralateral nostril compared with a midline target (average 384.11 vs 235.31 mm; p < 0.05). CONCLUSIONS Bone removal from the medial aspect of the lesser sphenoid wing, including the anterior clinoid process, may increase the exposure and surgical freedom of the extended endoscopic endonasal transtuberculum transplanum approach over the lateral segment of the anterior skull base. Although this study represents a preliminary anatomical investigation, it could be useful to refine the indications and limitations of the endoscopic endonasal corridor for the surgical management of skull base lesions involving the lateral portion of the planum sphenoidale.

Identification of the Extradural and Intradural Extension of Pituitary Adenomas to the Suprasellar Region: Classification, Surgical Strategies, and Outcomes

“…All patients underwent surgical treatment via the endoscopic endonasal approach (EEA). The expanded endoscopic endonasal approach (EEEA), transsphenoidal transtuberculum approach, is a valuable treatment option for PAs with significant SSE (12)(13)(14)(15)(16). However, it remains unclear how deep a tumor must extend into the suprasellar region to require EEEA.…”

Endoscopic endonasal surgery for anterior skull base meningiomas

“…Endoscopic approaches are an extension of this minimally invasive keyhole philosophy and, in carefully selected patients, they may be an excellent alternative due to the midline location of these tumors, offering a direct line of site from an endonasal approach without brain retraction [5,6,8,[12][13][14] . Furthermore, bilateral optic canal decompression can be safely and effectively accomplished in patients with compressive optic neuropathy from tumor extension into the medial optic canals [15][16][17] .…”

Endoscopic Endonasal Supraoptic and Infraoptic Approaches for Complex “Parasuprasellar” Lesions: Surgical Anatomy, Technique Nuances, and Case Series

“…Nevertheless, there are few reports regarding the endoscopic anatomy and how to effectively manage lesions involved in these areas. [10,11] For this reason, we sought to undertake a thorough anatomical description of the lateral aspect of the planum sphenoidale and a tight junction region of the OC, ACP, and ICA and its dural rings. These regions are located on the lateral area of the suprasellar region, the "parasuprasellar" area.…”

“…Nevertheless, few reports exist on the detailed anatomy of the lateral area of the suprasellar region, including the lateral aspect of the planum sphenoidale and a tight junction region of the optic canal (OC), the anterior clinoid process (ACP), and the internal carotid artery (ICA) and its dural rings that x its courses. [10,11] There are essentially two reasons for such limited data: 1) limited access to these regions due to obstruction of vital neurovascular structures such as the optic nerve (ON) and ICA; 2) these regions are considered off-limits due to the lateral-seated location and intrinsic anatomical complexity. In fact, it is di cult to imagine the existence of such high density of neurovascular and osseous as well as dural structures in such a narrow anatomic space.…”