GLABELLAR APPROACH - SIMPLIFIED MIDLINE ANTERIOR SKULL BASE APPROACH

As a simplified microsurgical technique for lesions at the midline ant erior skull base, a glabellar approach through a small incision (5 cm) between the eyebrows crossing the nasion was developed in four cadave r dissections. To determine the ideal positioning of the patient, the angle of the surgical trajectory was measured in the sagittal plane. I n an effort to make an operation simple and accurate through this limi ted exposure, measurements were made in distance from the midline nasi on to various intradural structures. Average distance from the midline point of the nasion (MPNa) to the midline of the tuberculum sella was 6.37 +/- 0.29 cm, 6.98 +/- 0.26 cm to the midline of the optic chiasm , and 8.00 +/- 0.11 to the lamina terminalis. In addition, measurement s to other various anatomical landmarks were made. The angle of the li ne drawn from the MPNa to the midline of the tuberculum sella was 5.2 +/- 1 degrees against a line drawn between the lateral canthus and the tragus (LC-T) in the sagittal plane. Based upon this study, the posit ioning of the patient's head would be better if the LC-T line the posi tioned at 25 degree extension when the operating microscope is set at 20 degree inclination. Within 6 to 8 cm in depth from the MPNa, import ant landmarks are exposed without brain retraction. If surgical instru ments are marked with ruler calibration, the depth of the surgical ins truments will suggest the anatomical location. This glabellar approach has been used in three patients successfully. A brain retractor was n ot necessary and not used during the operations. This technique provid es key exposures to the midline anterior skull base.