Localization method: Brow arch midpoint, nasal spine – saddle, nasal spine angle localization method: The length of the line connecting the midpoint of the saddle base (A) and the anterior nasal spine (B) and the angle between the midpoint of the brow arch (C) and the anterior nasal spine are measured on the CT midline sagittal tomography film before surgery, the length is 5-8cm, the average is 6.8cm, the angle is 56°-64°, the average is 60°, and the corresponding film is cut according to the A-B-C angle and length during surgery. The corresponding film can guide the angle and depth of the surgical approach.
Anatomical landmark positioning method: nasal septum and plow bone to determine the midline structure: preoperatively, according to the coronal CT, the nasal septum and plow bone are determined to be centered, and the nasal mucosa is strictly separated along the nasal septum to the plow bone to ensure that the approach does not deviate from the midline. The opening of the pterygoid sinus and the body of the plow bone are the signs of the anterior wall of the pterygoid sinus: the opening of the pterygoid sinus is usually the upper limit of the anterior wall of the pterygoid sinus, and the body of the plow bone is the pneumatized pterygoid sinus. The septum of the pterygoid sinus is an important marker for further correction of the midpoint of the saddle base: the number and position of the septum of the pterygoid sinus vary, and measuring the septal offset distance in advance can suggest the exact position of the midpoint of the saddle base. The morphology of the saddle base provides a sign of the midpoint of the saddle base: the saddle base is usually bowed and elevated in the cavity of the pterygoid sinus, and its highest point is the midpoint of the saddle base. It often has a bony protrusion of the pterygoid sinus septum attached to it, which is a further guide for localization. Bone destruction in the saddle area provides localization markers: preoperative CT and X-ray films of the damaged skull base in the saddle area are carefully studied to measure the relationship between the broken area and the saddle base clearly, and the location of the corresponding saddle base can be found when the broken area is exposed intraoperatively.
The sublabial-nasal septum-paranasal sinus approach is the most common type of transsphenoidal approach for saddle area tumor resection. Since 1907, Cushing has used this approach with poor results, high mortality, poor illumination instruments and lack of antibiotics, and inadequate exposure of the suprasellar septum tumor. Therefore, the development was stalled for a while. Later on, with the application of TV X-ray fluoroscope and microscope, some of the problems of delicate operation were solved and the operation was given a new life. However, so far X-ray lateral films and TV X-ray machine are still the necessary methods to locate the approach, and we have made some attempts to see whether it can be directly located. According to Guiot et al.’s grading of tumor damage to the saddle base, we strictly selected 122 cases with indications of grade 1-4 and O, A, E tumors and performed microscopic resection through sublabial-septum-pterygoid sinus approach, and adopted our own generalized non-X-ray integrated positioning method, which made the operation time significantly shorter than that of X-ray positioning method. The method of applying the A-B-C angle to measure the position and depth of the saddle base, because the length of the A-B and B-C lines are 6-8 cm, the actual measurement of the angle between the two lines is more accurate, but the obstruction of the sterile sheet and Cushing’s retractor during the operation hinders the actual measurement, and the B-C line needs to be estimated, which has a certain error. The combination of anatomical landmark localization method, including a series of landmarks on the way to the surgical approach (nasal septum positioning midline structure, pterygoid sinus opening and plough bone body suggesting the position of anterior wall of pterygoid sinus, the morphology of the saddle base and the degree of destruction and the position of the septum of pterygoid sinus can determine the position of the saddle base), then can achieve the purpose of accurate determination of the saddle base position. To summarize the experience of this method, we are required to make full use of the imaging data, carefully analyze all the information that may be related to the localization, and use it during the operation to obtain good results. Also avoid selecting cases with poor pneumatization of the pterygoid sinus and oversized pterygoid sinus. The method has been clinically validated and has some value for use.