Pituitary adenoma is the most common tumor in the saddle area, accounting for approximately 10% to 15% of intracranial tumors treated by surgery. Since 1909, when Cushing et al. pioneered the treatment of pituitary adenoma by transsphenoidal surgery, this treatment method has been adopted by the majority of neurosurgeons and has achieved good results.
I. Symptoms and signs
The main symptoms are endocrine changes and visual acuity and visual field disorders, some patients have headache and increased intracranial pressure. According to the endocrine hormone test, the tumor can be divided into non-functional and functional tumors (including GH adenoma, PRL adenoma, ACTH adenoma and TSH adenoma).
Imaging examination
Head X-ray, CT scan or MRI examination can help to diagnose pituitary adenoma. Tomogram of the pterygoid saddle often shows enlargement of the pterygoid saddle and thinning or destruction of the saddle base bone. MRI can show the tumor shape and its relationship with the surrounding structures more clearly, especially for the diagnosis of pituitary microadenoma. According to the imaging examination, pituitary adenoma can be classified into five grades, namely grade 1: the tumor is less than 10 mm in diameter and grows in the saddle; grade 2: the tumor extends up to 10 mm and fills the suprasellar pool; grade 3: the tumor extends 10 mm to 20 mm and elevates the third ventricle; grade 4: the tumor extends 20 mm to 30 mm and fills the anterior third ventricle. Grade 5: tumor extends >30mm into the saddle and reaches the foramen magnum of the lateral ventricle, often combined with obstructive hydrocephalus. Grade 1 of this classification is microadenoma, grades 2 and 3 are large adenoma, and grades 4 and 5 are giant adenoma.
Surgical treatment
The surgery is performed under general anesthesia with the patient in the prone position with the head tilted back at 30°, and the anesthesia cannula of the trachea is fixed at the left corner of the mouth. During the operation, the pterygoid sinus and the bone of the saddle base were opened using cold light source deep illumination and high-speed micro-abrasive drill. After entering the pterygoid saddle, the tumor was separated and removed under the surgical microscope. The pituitary microadenoma tissue is mostly white or purplish-red in color and is easy to peel and remove. For large adenoma or giant adenoma, after removing the tumor tissue in the saddle, in order to obtain complete removal of the tumor protruding into the saddle, saline is slowly injected into the catheter preplaced in the subarachnoid space of the patient’s lumbar region, and the intracranial pressure is increased to squeeze the suprasellar tumor into the operative field, which facilitates the surgical removal. The amount of saline injection depends on the monitored intracranial pressure, generally 20ml-60ml, a few are 80ml. if ICP>5.33kPa, special care should be taken, too much or too fast injection may produce acute intracranial pressure increase and cause serious complications. After tumor resection, tight hemostasis was performed and the tumor cavity was blocked with a small piece of gelatin sponge. Small pieces of muscle and bone were taken for saddle base repair, and the local area was reinforced with medical adhesive to prevent CSF leakage or pituitary dislocation, and the nasal cavity was blocked with iodoform or oil sand strips.
IV. Post-operative experience and complications
Postoperative antibacterial agent was applied to control the infection, and the blockage in the nasal cavity was removed on the 4th day, and the stitches of the wound were removed on the 7th day. The most common postoperative complications were polydipsia and polyuria, followed by CSF nasal leakage, all of which could be cured by taking active measures.
V. Discussion
(A) Advantages of transsphenoidal surgery development
Transsphenoidal surgery for pituitary adenoma has undergone more than 80 years of practice and development, making this treatment technique perfected. In particular, since the 1960s, Professor Hardy has advocated the use of the operating microscope, which, with its magnification and illumination advantages, has greatly improved the exposure of the operative field. Since the 1970s, with the application and improvement of the operating microscope, operating instruments and intraoperative X-ray monitoring devices, as well as the advent of advanced neuroimaging and radioimmunoassay methods, pituitary adenomas, especially microscopic adenomas, have been treated at an early or ultra-early stage. The early or ultra-early diagnosis of pituitary adenomas, especially microadenomas, has become possible. Surgery for pituitary adenomas is no longer only aimed at optic nerve decompression, but rather at reducing hormonal hypersecretion. As a result, the transsphenoidal approach to pituitary adenoma surgery has received great attention and has developed considerably. Transsphenoidal surgery has shown excellent results in the treatment of not only microadenomas but also large pituitary adenomas that break through the saddle septum. Over the years, the authors have shown a high rate of transsphenoidal approach to pituitary adenoma treatment, and patients generally recover quickly after surgery with few complications and no surgical deaths. This fully indicates that this procedure has obvious features and advantages and is a treatment that deserves to be carried out widely.
(B) Selection of indications for transsphenoidal surgery
The former aims to relieve the occupying effect of the tumor and to achieve sufficient decompression of the optic nerve and pituitary area; the latter aims to restore the neuroendocrine function as soon as possible after removal of the tumor. In view of the many advantages of transsphenoidal surgery to remove pituitary adenoma, it is important to master the indications for this surgical approach. Over the years, the authors have accumulated some experience in the selection of surgical indications by referring to the literature on this procedure at home and abroad. The authors believe that the following are good indications for transsphenoidal pituitary adenoma resection: 1. pituitary microadenoma; 2. pituitary adenoma invading into the pterygoid sinus; 3. pituitary adenoma of the optic cross anterior type; 4. pituitary adenoma extending into the saddle, but not dumbbell-shaped, and not invading into the saddle, and the imaging examination suggests that the tumor is soft and loose; 5. advanced age and frailty, and cannot tolerate open craniotomy. Contraindications are: 1. pituitary adenoma extending to the suprasellar area, dumbbell-shaped, and hard on imaging; 2. large part of the tumor residing in the suprasellar area, inverted gourd-shaped; 3. pterygoid sinus dysplasia; 4. inflammation of paranasal sinuses and nasal cavity.
It is usually believed that it is difficult to use transsphenoidal surgery to extend pituitary adenoma to the suprasellar area, but with the accumulation of surgical experience, it has become possible to perform some surgeries that were considered difficult in the past. The experience of Satio et al. shows that the results of transsphenoidal surgery for large pituitary adenomas with suprasellar extension >30 mm are very satisfactory, and the results of postoperative follow-up (average 10 years) show that 74% of patients’ symptoms disappeared.
(C) Key points of transsphenoidal surgery
The basic requirements of the transsphenoidal approach are to operate through the pterygoid sinus, open the saddle base, and reveal the anterior pituitary lobe. The tumor tissue is explored and removed, and postoperative complications are prevented. Currently, two approaches are widely used: the sublabial-septum-pterygoid sinus approach and the transnasal vestibule-septum-pterygoid sinus approach. For example, the sublabial-septum-pterygoid approach is not detrimental to the face, but the incision is prone to infection, and the upper incisors will have soreness and numbness for a period of time; the transnasal vestibule-septum-pterygoid approach has a slightly shorter anatomical path, but it is detrimental to the face. In order to avoid serious complications during and after the operation, the following operation points are proposed for reference: 1, according to the CT coronal and axial scans to determine the pterygoid sinus and the saddle bottom entry mark, generally the septum of the pterygoid sinus is located in the center of the saddle bottom, this is the mark to enter the saddle bottom, or do not need to use X-ray positioning; 2, using a miniature grinding drill to open the saddle bottom strictly along the center of the pterygoid saddle, do not deviate from the midline, to prevent injury to the internal carotid artery or cavernous 3.For large pituitary adenomas that extend to the saddle, the saddle should be removed first, and then the subarachnoid cavity should be injected with saline and the intracranial pressure should be increased to facilitate the downward movement of the saddle to the operation field to facilitate the resection; 4.After resection of the tumor, the saddle septum should drop, and at this time there is CSF overflow, and muscle tissue and bone pieces should be taken and glued with medical adhesive to repair the saddle base to prevent CSF nasal leakage after surgery; 5.For children 5. For children or those with dysplastic pterygoid sinus, a high-speed micro-abrasive drill can be used to access the saddle base through the “A-mediated” pterygoid sinus under X-ray surveillance in order to remove the tumor.
Larger Pituitary Adenoma refers to a pituitary tumor that grows from the saddle to the upper saddle and is >10mm in diameter,
It includes large pituitary adenoma and giant pituitary adenoma, and about half of the clinical cases are non-functional adenomas. The traditional treatment for LPA is craniotomy, but in recent years, the number of microsurgical resection by transsphenoidal approach has been increasing. We have performed transsphenoidal microsurgery for LPA and achieved good results.
The dura mater and tumor membranes were cut open and the tumor tissue was seen to spill out in dark gray, milky white or purplish red. After resection of the intra-saddle tumor, in order to obtain complete removal of the tumor protruding into the saddle, saline was slowly injected into the catheter preplaced into the subarachnoid space, and the intracranial pressure was increased to squeeze the tumor into the saddle to facilitate smooth removal. After removal of the tumor, the saddle diaphragm is seen to descend into the operative field as a blue round protrusion containing clear cerebrospinal fluid, which should be carefully protected and should not be damaged. If the saddle diaphragm is broken, cerebrospinal fluid will flow out continuously, so repair is performed. After tight hemostasis, small pieces of muscle and bone are taken to repair the saddle base, and local medical adhesive is applied to reinforce it to prevent pituitary dislocation or CSF leakage. The nasal cavity was filled with iodoform or oil sand strips, and the lips were wrapped with gauze under pressure.