Object: Minimally invasive approaches have been proposed for the treatment of anterior cranial base pathology. Whereas earlier studies have quantified surgical exposure by referring to the opening on the surface, this cadaveric morphometric study redefines the concept of working area by examining the deep exposures afforded by several different approaches. Specifically, the authors systematically quantify and compare the operative exposure afforded by the pterional, supraorbital, and transorbital keyhole approaches to the sellar, suprasellar, and perisellar regions, including the anterior communicating artery complex.
Methods: Pterional, supraorbital, and transorbital approaches were sequentially performed in 5 embalmed cadaveric heads on both sides. Preoperative and postoperative CT scans were obtained for frameless stereotactic navigation and measurements. Using reproducible anatomical landmarks, 6 triangles were defined to systematically measure the working area, depth of the surgical window, and angle of observation for each approach. Areas of the triangles were calculated using the Heron mathematical formula based on stereotactic navigation measurements. Ten sets of data were analyzed.
Results: The pterional, supraorbital, and transorbital keyhole approaches provided progressively increasing working areas. The transorbital approach was associated with significantly increased exposure when compared with the pterional approach (p < 0.01). The transorbital approach was associated with a shallower depth of the surgical window when compared with either the supraorbital (p < 0.05) or pterional (p < 0.01) approach. The angle of basal view increased 56.6% with the transorbital approach (p < 0.001) when compared with the supraorbital approach. The transorbital route provided greater exposure on deeply located midline and contralateral structures.
Conclusions: In refining the concept of working area as deep rather than superficial in the surgical field, the authors quantified the 6 triangles whose boundaries were relative to the target structures to be exposed in the approach. The authors' morphometric findings support the use of the supraorbital and transorbital approaches as a valid alternative to the pterional approach for the treatment of sellar and perisellar pathology. The transorbital approach combines the advantages of minimal invasiveness with those of cranial base techniques.