The procedure is performed with an endoscope as the only optical tool throughout the operation, i.e., pure endoscopic surgery, and not using the microscope with the endoscope, i.e., endoscope-assisted microsurgery.
Only rigid endoscopes without a working channel, 4 mm in diameter; 0°, 30°, and 45° angled lenses; and 18-30 cm in length are employed. They must be inserted into an outer sleeve that, when connected to an irrigation system, clears the lens. Surgical instruments are introduced through the same nostril alongside the endoscope. The endoscope is connected to a monitor and a video recording unit by means of a video camera and is illuminated through an optical fiber cable using a xenon light source. The majority of the operation is performed with a 0° endoscope using the angled lenses (30°, 45°) for further exploration of the intrasellar cavity and the suprasellar region. During the procedure, the endoscope is held by the surgeon's non dominant hand until the sphenoid sinus is entered, then an adjustable endoscope holder is fixed to the surgical table, providing a fixed image of the operating field and freeing both of the surgeon's hands.
Neurosurgeons who are experienced in microscopic transsphenoidal surgery still require practice to overcome the steep learning curve, caused mainly by the absence of the standard nasal speculum. Despite a wider working angle enabling more structures to be seen simultaneously, the narrow working space is difficult to get used to. With the loss of the speculum, which provides a sense of surgical scale, the surgeon must be careful to avoid quick movements close to the surgical target, because the endoscopic image is two dimensional. It is possible to lose depth perception inside the nasal cavity and the sphenoid sinus, increasing the risk of serious damage. Careful in-and-out movements with the endoscope give the surgeon set points at different depth levels of the surgical route and recover the three-dimensional sense of depth.
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