The anterolateral triangle as window on the foramen lacerum from transorbital corridor: anatomical study and technical nuances

Abstract

Objective: Neurosurgical indications for the superior eyelid transorbital endoscopic approach (SETOA) are rapidly expanding over the last years. Nevertheless, as any new technique, a detailed knowledge of the anatomy of the surgical target area, the operative corridor, and the specific surgical landmark from this different perspective is required for a safest and successful surgery. Therefore, the aim of this study is to provide, through anatomical dissections, a detailed investigation of the surgical anatomy revealed by SETOA via anterolateral triangle of the middle cranial fossa. We also sought to define the relevant surgical landmarks of this operative corridor.

Methods: Eight embalmed and injected adult cadaveric specimens (16 sides) underwent dissection and exposure of the cavernous sinus and middle cranial fossa via superior eyelid endoscopic transorbital approach. The anterolateral triangle was opened and its content exposed. An extended endoscopic endonasal trans-clival approach (EEEA) with exposure of the cavernous sinus content and skeletonization of the paraclival and parasellar segments of the internal carotid artery (ICA) was also performed, and the anterolateral triangle was exposed. Measurements of the surface area of this triangle from both surgical corridors were calculated in three head specimens using coordinates of its borders under image-guide navigation.

Results: The drilling of the anterolateral triangle via SETOA unfolds a space that can be divided by the course of the vidian nerve into two windows, a wider "supravidian" and a narrower "infravidian," which reveal different anatomical corridors: a "medial supravidian" and a "lateral supravidian," divided by the lacerum segment of the ICA, leading to the lower clivus, and to the medial aspect of the Meckel's cave and terminal part of the horizontal petrous ICA, respectively. The infravidian corridor leads medially into the sphenoid sinus. The arithmetic means of the accessible surface area of the anterolateral triangle were 45.48 ± 3.31 and 42.32 ± 2.17 mm² through transorbital approach and endonasal approach, respectively.

Conclusion: SETOA can be considered a minimally invasive route complementary to the extended endoscopic endonasal approach to the anteromedial aspect of the Meckel's cave and the foramen lacerum. The lateral loop of the trigeminal nerve represents a reliable surgical landmark to localize the lacerum segment of the ICA from this corridor. Nevertheless, as any new technique, a learning curve is needed, and the clinical feasibility should be proven.

Keywords: Endoscopic transorbital; Foramen lacerum; Meckel’s cave; Middle fossa triangles; Vidian nerve.

Fig. 1

Superior eyelid transorbital endoscopic approach (SETOA) to the middle cranial fossa (right side). a Skin incision on a wrinkle of the upper eyelid and carried in the depth through the orbicularis oculi muscle (OOM) and extended laterally until to expose the fronto-zygomatic suture (FZS); b after the subperiosteal/periorbital dissection was performed up to identify the superior (SOF) and inferior orbital fissures, the corridor between the periorbit (PO) content medially and the greater sphenoid wing (GSW) forming the lateral wall of the orbit, laterally, is exposed; c exposure of the temporal lobe pole dura mater (TLd) and the sagittal crest (SC) after the drilling of the lateral wall of the orbit; d interperiosteal/dural dissection of the cavernous sinus lateral wall and of the middle fossa with identification of the midsubtemporal ridge (MSR) at the base of the anterolateral triangle between the foramina rotundum and ovale; e flattening of the middle fossa floor and exposure of the III and IV cranial nerves, the trigeminal nerve with its ganglion (GG), branches (V1, V2, V3), and lateral loop (LL) inside the periosteal layer; f drilling of the anterolateral triangle with skeletonization of the vidian nerve (vn). (FZS, fronto-zygomatic suture; OOM, orbicularis oculi muscle; GSW, greater sphenoid wing; SOF, superior orbital fissure; PO, periorbit; TLd, temporal lobe dura; SC, sagittal crest; GG, gasserian ganglion; ACP, anterior clinoid process; LL, lateral loop, MSR, mid-subtemporal ridge)

Fig. 2

Imagine guidance from neuronavigation system showing measurements of the anterolateral triangle vertices from endonasal (a–c) and transorbital perspectives (d–f). Foramen Rotundum from endonasal (a) and transorbital (d) perspectives; foramen ovale from endonasal (b) and transorbital (e) perspectives; lateral loop of trigeminal nerve from endonasal (c) and transorbital (f) perspectives

Fig. 3

Exposure of the content of the anterolateral triangle of the middle cranial fossa through SETOA (right side). a Identification of a quadrangular space (red dotted line) and its content (lacerum ICA, vidian nerve, foramen lacerum, lower clivus, medial aspect of Meckel’s cave) limited by the inferior border of V2, superiorly, the superior border of V3, posteriorly, the line crossing the most anterior limit of exposure of the vidian nerve and joining the foramen rotundum and the point where the greater wing joints the body of the sphenoid bone, anteriorly, and the line connecting this last point and the foramen ovale inferiorly; b identification of the supravidian and infravidian windows, divided by the course of the vidian nerve from its distal end of exposure up to its disappearing behind V3, and of the related disclosed corridors: the “medial supravidian” and the “lateral supravidian,” divided by the lacerum segment of ICA, and leading to the lower clivus, and to the medial aspect of the Meckel’s cave and to the distal end of the horizontal segment of the petrous ICA, respectively; c expanded view of the “medial supravidian corridor” after gentle upward displacement of V2; d expanded view of the “lateral supravidian corridor” after gentle lateralization of the gasserian ganglion. (GG, gasserian ganglion; Lac ICA, lacerum internal carotid artery; CLIV, clivus; FL, foramen lacerum; vn, vidian nerve; MC, Meckel’s cave; cICA, cavernous internal carotid artery; pICA, petrous internal carotid artery; LL, lateral loop)

Fig. 4

Exposure of the foramen lacerum region through endoscopic corridors before (a–b) and after (c–d) removal of the vidian nerve (left side). The exposure and working areas of the foramen lacerum, medial aspect of Meckel’s cave, and lower clivus increases after resection of the vidian nerve (c–d)

Fig. 5

Exposure of the foramen lacerum region through endoscopic transorbital (a, c) and extended endonasal transclival (b, d) corridors before (a–b) and after (c–d) removal of the vidian nerve (left side). The lateral-to-medial trajectory provided by the transorbital approach through the anterolateral triangle represents a complementary surgical route to the medial-to-lateral trajectory provided by the endonasal corridor to the foramen lacerum region. (GG, gasserian ganglion; Lac ICA, lacerum internal carotid artery; CLIV, clivus; FL, foramen lacerum; vn, vidian nerve; LL, lateral loop; PLL, petro-lingual ligament)

Fig. 6

Artistic draws, axial (a) and coronal (b) views. Complementary extended endoscopic endonasal (EEEA) and superior eyelid endoscopic transorbital (SETOA) approaches to the lesion of lacerum foramen and medial aspect of Meckel’s cave