The difficulty of pituitary tumor surgery is measured by two indicators: exposure of the tumor and resection of the tumor.
1.Suprasellar approach The saddle nodes and the pterygoid plateau are removed with a high-speed grinding drill, and the bone window is enlarged and flattened with a small kerriso bite forceps. The bone window can be enlarged forward to 1.5-2 cm, taking care not to exceed the anterior wall of the pterygoid sinus. In the lateral direction, the optic canal bulge is used as a border. After dissection of the dura, the tumor is removed starting from the inferior and lateral directions to avoid premature descent of the residual septum, which would obscure the lateral and posterior views and result in incomplete removal of the tumor in these areas.
After partial resection of the suprasellar tumor, the tumor envelope can be separated from the compressed pituitary gland. However, giant pituitary tumors usually grow into the subarachnoid space, so the surrounding neurovascular structures need to be carefully separated with microscopic scissors sharply.
The advantage of this expanded surgical approach is that it provides dual access for resection of suprasellar tumors, allowing for intra-tumoral resection and decompression by operating within the envelope through the first access, and separation of the envelope from the surrounding neurovascular adhesions through the second access, outside the envelope.
Finally, a 30° or 45° angled endoscope is used to examine the blinded area of the visual field for tumor remnants. This link is of great significance, especially for huge pituitary tumors growing intracranially, because the outer residual tumor often has the risk of bleeding, which can lead to serious postoperative complications or even death.
2.Cavernous sinus approach For pituitary adenomas infiltrating into the cavernous sinus, different areas of the cavernous sinus can be reached through two different passages.
One access is to reach the medial aspect of the internal carotid artery and is indicated for pituitary tumors infiltrating into the medial wall of the cavernous sinus. The tumor itself enlarges the parasternal internal carotid artery in part c such that the tumor tissue can be easily aspirated or scraped out through this channel.
The second channel is to reach the lateral aspect of the cavernous sinus and is indicated when the tumor infiltrates the entire cavernous sinus (e.g. knosp grade 4 pituitary tumor). This pituitary tumor primarily invades the lateral portion of the cavernous sinus, often displacing the medial portion of the internal carotid artery and pushing the cranial nerve structures outward.
This pituitary tumor can be exposed by widening the channel, at the level of the anterior wall of the pterygoid sinus, smoothing the pterygoid process and the closed bony portion between the pterygoid canal and the foramen ovale. These operations allow exposure of the pterygoid fossa and make possible the resection of pituitary tumors that infiltrate this area. By precise scraping out or suctioning operations, the tumor tissue in the parasternal area can usually be removed. Since the actinic nerve is often pushed outward by the tumor, the intra-saddle portion can be safely removed in the same manner.
3.Intranasal and paranasal surgical access When a giant pituitary tumor grows into the intra-nasal or paranasal sinus, surgical resection needs to be achieved through a lower surgical access. The specific surgical access needs to be decided according to the degree of infiltration of the pituitary tumor, so in this surgical access, it is often necessary to remove part of the structures in the intranasal or paranasal area in order to be able to obtain a wider surgical field and provide convenience for the operation of surgical instruments.
If the pituitary tumor grows downward and reaches the slope and nasopharynx, removal of the prominence and base of the pterygoid sinus is critical; if the entire pterygoid sinus is invaded, removal of the posterior portion of the nasal septum may be required.