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.
