Three Different Routes to Reach to the Meckel's Cave Region: An Anatomical Study

Background The anterolateral corridor via expanded endoscopic endonasal approach (EEA) represents an approach through of the quadrangular space (QS) to reach the Meckel's cave. Management of lesions of the ventral surface of the Gasserian ganglia is performed through the pterygopalatine approach, with mobilization or sacrifice of the vidian nerve to reach the QS. Relevant anatomical structures surrounding the quadrangular space have not been studied in detail. We describe three routes to expand the area of approach of the quadrangular space: (1) retrocarotid, (2) transpterygopalatine—vidian nerve, and (3) transpterygopalatine—mandibular strut.

Methods Five cadaveric injected specimens underwent an EEA. We used 0- and 45-degree scopes. The quadrangular space was dissected and analyzed with three anatomical routes: (1) retrocarotid space, (2) transpterygopalatine—vidian nerve, and (3) transpterygopalatine—mandibular strut. Advantages and limitations were analyzed in each one. We used a three-vector coordinate system to analyze the Meckel's cave and the radius, or target, was the Gasserian ganglia.

Results Each route was analyzed and described as follows: (1) The retrocarotid space is the medial route to reach the Meckel cave. The middle clivus was drilled and the boundaries of this route were Dorello canal superiorly, foramen lacerum inferiorly, middle clivus medially and the paraclival carotid laterally. The limitation of this route is the mobilization of the paraclival carotid, and the advantage was to reach the medial and anterior part of the Meckel's cave. (2) Transpterygopalatine—vidian nerve is the common route to reach the anterior part of the Meckel's cave through the QS. The limitation is the vidian nerve, and in a majority of cases, it is necessary to cut to access this space. The advantage is that is allows for proper control of the petrous carotid. (3) The transpterygopalatine—mandibular strut approach exposed the strut between V2 and V3, which we referred to as the mandibular strut. This route allows us to work in the anterior and the lateral part of the QS and expand the area to the anterolateral triangle of the cavernous sinus. The limitation of this approach is it is more risky due to close proximity of the cavernous sinus.

Conclusion The quadrangular space is a difficult corridor to understand surgically. The important landmarks are the vidian canal and the limits of the quadrangular space, which is bounded by the ICA medially, V2 laterally, the horizontal petrous ICA inferiorly, and abducens nerve superiorly. Understanding the anatomic landmarks and boundaries of this space, using an endonasal approach, is important in the final resection of lesions in this area. We have developed three anatomical routes toward Meckel's cave (medial, anterior, and lateral). These routes create an expansion of the classic approach of the QS for maximizing resection of a lesion without increased morbidity.