Microanatomy Study Of Endoscope-asisted Keyhole Approaches Via Anterior Skull Base-supreaorbital Or Glabellar Approach

Objective To study the detailed micrpanatomy of endoscope-assisted supraorbital or glabellar ' keyhole' approaches via anterior skull base, and discuss the clinical feasibility to reach Willis's circle and its adjacent structure via the approaches, preparing for its clinical application.Methods 20 adult cadavers head soaked in fomalin were studied and measured with microscope and endoscope alternatively via ' keyhole1 approaches, which located between posterior border of frontomatar and external border of sphenoidal ridge .Transverse incision was made 3.5~5cm above zagomatic arch and the skull window was about 2.5-3cm in diameter. The operative corridor was between subdural and epiarachnoid space, from frontal base surface to posterior border of sphenoidal ridge . The Willis's circle and adjacent regions could be reached via these approaches.Results The incision is located lateral to the eyebrow end. and the key hole is located at a dimple of lateral great wing surface between zygomatic process and sphenoid crest. The operative corridor is between the dura and arachnoid via the two approaches, the Willis circle, sella, cavernous sinus and petroclivus area, even contralateral ICA , the third ventrical floor and longitudinal can be reached.Conclusions (1) The ' keyhole' technique is selected individuallydepend on conditions of the imaging examination as well as the lesion of the patient. It is a minimally invasive technique and can reduce the operative trauma. Supraorbital and glabellar ' keyhole' approaches are effective anterior skull base approaches .(2) The major factor for correctly reaching the lesion is to approach according to certain anatomic marks but not the approaching angle and depth. (3) The approaches are in the epiarachnoid space and the arachnoid should be kept intact to protecting brain dcbri covering the visual field. (4) The marks of road mapping for the approaches include frontal base , sphenoid crest, margin of sphenoidal crest, anterior clinoid process . optic nerve and Ci segment, also it is important that the path way of road mapping for the approaches need to be kept in mind.