Resection of the medial wall of the cavernous sinus

The cavernous sinus is a large venous sinus located directly next to the pituitary gland. Important cranial nerves and the internal carotid artery (arteria carotis interna) pass through it. The pituitary gland drains some of its venous blood through small natural openings in the inner wall of the cavernous sinus. Cells from a pituitary adenoma can also enter the wall or the cavernous sinus through these openings. How often this occurs depends, among other things, on the type of tumor *.

In the past, the cavernous sinus was generally not opened during pituitary surgery; as a result, tumor fragments in this area were often left behind. Today, modern endoscopes and specialized instruments allow for the targeted removal of these tumor fragments and the affected wall in selected patients.

Whether the medial wall of the cavernous sinus should be removed depends on various factors:

• Type of tumor
• Extent of infiltration
• Patient's age
• Treatment alternatives
• Individual surgical risk

It is particularly important to distinguish between non-functioning pituitary adenomas and hormonally active pituitary adenomas.

In the case of non-functioning adenomas, removal of the wall is usually not warranted, especially in older patients. A small residual tumor can often be monitored with regular checkups or, if necessary, treated with radiation therapy.

In cases of functioning adenomas ––such as those associated with Cushing’s disease or acromegaly– it is particularly important to remove the tumor as completely as possible. Even a small number of remaining tumor cells in the cavernous sinus or its wall can lead to continued excessive hormone production.

In carefully selected cases, removal of the medial wall can therefore improve the prognosis for hormonal remission *, *, *, *. This challenging technique should only be performed at centers with appropriate experience.

The surgery is performed endoscopically through the nose and is part of the procedure to remove the pituitary adenoma. After the main portion of the tumor has been removed, the surgical team proceeds step by step:

• Incision: First, the anterior wall of the cavernous sinus is carefully incised.
• Hemostasis: Since this is a venous blood vessel, the area is filled with a special foam paste and temporarily packed to control bleeding.
• Detachment of the wall: The medial wall is gradually incised at its lower and upper attachment points and detached from the surrounding structures.
• Removal: The detached portion of the wall can then be removed along with any tumor tissue and examined histologically.

The internal carotid artery and important cranial nerves run through the cavernous sinus. Therefore, injury to these structures cannot be ruled out. The individual risk depends on the anatomy and the extent of the tumor and will be discussed in detail before surgery.

• Injury to the internal carotid artery: This complication can be serious. Data published to date indicate a very low rate among experienced surgical teams; however, the original text does not provide a specific percentage for this.
• Temporary cranial nerve palsy: This may manifest primarily as double vision and occurred in 7.1 % of patients in one study *. Function usually recovers completely, but recovery may take several months.