Endoscopic pituitary gland transposition techniques to the interpeduncular and prepontine regions: an anatomical study

Objective: The floor of the third ventricle and the interpeduncular and prepontine regions represent challenging surgical targets. The expanded endoscopic endonasal approach (EEA) with pituitary gland (PG) transposition has been proposed to provide direct access to these anatomical regions. Through the years, different endoscopic PG transposition techniques have been studied and presented. The goal of this study was to compare the techniques, relevant anatomy, and surgical exposure of extradural, intradural, and interdural PG transposition techniques.

Methods: Six formalin-fixed, latex-injected cadaveric head specimens were used to perform the EEA with extradural, unilateral interdural, and unilateral intradural PG transpositions. The interpeduncular and prepontine regions and the neurovascular structures located within these cisterns were carefully exposed and analyzed. The maximal cranial, caudal, and lateral accessible points within the surgical field were identified for each approach. Consequently, the relative craniocaudal and horizontal surgical axes were measured to quantify the extent of accessibility of each approach.

Results: The extradural PG transposition technique provided the largest horizontal extensions and bilateral access to structures within the interpeduncular and prepontine regions; the mean horizontal axis was 17.9 (range 13.9-20.4) mm. The unilateral interdural PG transposition provided wider vertical exposure, with a mean craniocaudal axis of 16.2 (range 13.0-20.9) mm. In this approach, the surgical field was extended cranially above the ipsilateral mammillary body (MB). The unilateral intradural PG transposition provided a similar surgical exposure to the interdural approach, with a mean craniocaudal axis of 14.7 (range 12.9-15.8) mm. The approach required significant manipulation of the PG after opening both periosteal and meningeal dura layers.

Conclusions: The extradural PG transposition is indicated for lesions of the upper clivus region that extend bilaterally and do not have a cranial extension beyond the MBs. The inter- and intradural PG transpositions are beneficial for unilateral lesions that extend cranially to the MBs. Both techniques require coagulation of the ipsilateral inferior hypophyseal artery. The intradural technique requires more manipulation of the PG, while the interdural technique requires opening and access to the cavernous sinus. If needed, the intra- and interdural techniques can also be performed bilaterally.