Through our study, we found that it can be judged before operation according to the characteristics of SPADSD, and reduce the probability of wrong diagnosis. SPADSD often grows on the saddle because there is no physical restraint. These tumors do not compress the pituitary, but rather they grow toward the upper unrestricted area. On MRI, we often note that the shape of the pituitary is normal. Nevertheless, the shape of the SPADSD is usually irregular, showing a lobular shape. There are few violations of the pituitary during surgery, and there are fewer cases of hypofunction of the pituitary after surgery.
SPADSD is an invasive pituitary tumor that manifests in several invasive modes. It can break through upwards towards the saddle to invade the anterior skull base or the third ventricle, and can invade the cavernous sinus or can surround the internal carotid artery growing to the saddle sides. At present, there is no relevant research demonstrating which surgical method is more suitable for the resection of the SPADSD. We combined with the advantages of endoscopic techniques to conduct an in-depth discussion and review of the treatment of this tumor. The growth patterns and imaging signals of SPADSD are often very similar to those other intracranial tumors; therefore, the clinician often has difficulty with the preoperative diagnosis and the choice of surgical methods. Below, we compare the characteristics of other common tumors in the sellar region with those of SPADSD, in hopes of reducing the misdiagnosis, better understanding their common growth patterns, and developing better treatment schemes.
Other types of pituitary adenomas in the suprasellar region
On preoperative MRI, pituitary adenomas often exhibit equal or low signal in T1, equal or high signal in T2, and uniform enhancement signal on enhancement. Normal pituitary tissue, because of the compression of the saddle tumor, shows a thin layer arc on enhanced imaging of the saddle region. Because of the absence of sellar diaphragm compression, SPADSD exhibits imaging and anatomical features that are different from those of other pituitary adenomas in the suprasellar region. Despite the similar signal shown by SPADSD, there is no typical “waist sign” or “snowman sign.” Their shape is irregular, and their position is located more on the saddle with fewer components in the sellar region. Therefore, the pituitary can assume a normal shape.
During the operation, attention should be paid to the following points: 1) The patient should be positioned gently leaning back; 2) When entering the nasal cavity, the middle turbinate should be removed, and a vascular mucosa flap should be prepared; 3) A bone window should be ground at least above the saddle nodule position, even reaching the sphenoidal platform; 4) After opening the dura mater, it is often found that there is no saddle diaphragm when separating tumor, and the tumor is closely adhered to the optic chiasm. Therefore, the tumor must be carefully separated from the arachnoid membrane along its membrane; 6) For the position of the third ventricle, the surgeon should attempt to create an in situ separation to reduce the risk of postoperative hypothalamic nuclear damage; 7) one should avoid electrocoagulation so as not to burn hypothalamic small perforating artery; 8) If the third ventricle floor is not properly preserved after tumor resection, the ventricular system should be opened to liberate cerebrospinal fluid circulation; 9) At 6 hours after surgery, the bleeding in the surgical area should be monitored so as to screen for acute hydrocephalus; 10) For reconstruction of the skull base after the extended transnasal approach, it is necessary to use multiple layers of repair to effectively prevent postoperative CSF.
SPADSD needs to be differentiated from craniopharyngioma. The latter originates from the pituitary stalk, and the lesion is often located in the suprasellar region. The normal pituitary can usually be observed on MRI. Tumors often appear as cystic and solid, and fewer solid tumors are often similar to pituitary adenomas. The composition of craniopharyngioma is complex; calcification is commonly seen on CT, and the signal is variable in MRI. The cystic part may have low, equal or high signal due to varying protein content, high signal or low signal in T2. The solid part has equal signal in T1, and slightly higher signal in T2. In the enhanced phase, the tumor parenchyma and the wall of the capsule show uneven enhancement. During the intraoperative resection of craniopharyngioma, it is necessary to determine the relationship between the tumor and the pituitary stalk. When the trans-infundibular craniopharyngioma is matched, the pituitary stalk should not be retained. At this time, the identification of pituitary adenomas is particularly important. The treatment of pituitary adenomas should not permanently damage the pituitary stalk. This is particularly important for differentiation of SPADSD from craniopharyngioma.
Tuberculum sellae meningioma
Roughly 8% of meningiomas occur in the saddle, and most originate from saddle nodules. On MRI, tumors show equal signals in T1 and T2, with clear boundaries, and a substantially uniform enhancement phase. The tumor grows along the meninges and on both sides, with frequent appearance of the meningeal tail sign. The difficulty in the treatment of saddle nodule meningioma is that the tumor is rich in blood supply and is connected to the surrounding blood vessels. Behind the optic chiasm, the adhesion is extremely tight. During treatment, particular attention should be paid to the relationship of the tumor to the superior pituitary and anterior cerebral arteries. The treatment of the relationship between the optic chiasm and the tumor is also applicable to SPADSD. Lacking effective dura mater or even separation of the arachnoid membrane, SPADSD is in direct contact with the optic chiasm. Therefore, during surgery, a bone window should be opened to the saddle nodule first, and the anterior skull base dura mater should be cut open to expose the optic chiasm that will lay the foundation for the subsequent step of treating the tumor behind the chiasm.
Advantages of endoscopic surgery
Compared with traditional microsurgery, endoscopic surgery enjoys better illumination and better visual effects, with expansion of the visual range because of the use of angle mirrors. The high-resolution image more accurately distinguishes the saddle and the arachnoid, visualizing the important structures around the internal carotid artery, the third ventricle, and the pituitary and tumor tissues, thereby protecting the pituitary. It has great advantages for treatment of suprasellar tumors. According to statistics, the endoscopic resection rate of suprasellar pituitary adenomas defined by Hardy classification is 96% . Abergel et al. compared patients undergoing EEA surgery and traditional craniotomy. They concluded that EEA had less impact on psychological and emotional aspects than did traditional craniotomy and patients enjoyed a better quality of life [17,18]. Nevertheless, the endoscopic transnasal approach is technically challenging for most neurosurgeons and has a longer learning period. EEA often increases the incidence of CSF. Nevertheless, with the development of endoscopic technology, EEA will gradually be widely used by clinicians .
Through the review of the relevant literature in the past 5 years, we prove that EEA has more advantages than traditional surgery in the treatment of pituitary tumors through the results of three related articles, they all performed a systematic review and meta-analysis performed a systematic review and meta-analysis. In 2014, Gao et al. performed 15 studies (n = 1,014 patients) among 487 studies that involved endoscopic surgery and 527 studies tha dealt with microscopic surgery. In 2015, Xu et al. evaluated 1888 patients from 14 studies and get the result that compared with microscopic group. In 2017, Li et al. assessed 2,272 patients with pituitary adenoma included in twenty-three studies. Through the relevant data and statistics, they have proved that the rate of gross tumor removal was higher in the endoscopic group than in the microscopic group and the post-operative hospital stay was significantly shorter for the endoscopic surgery group. But there was no significant difference between the two techniques in the incidence rates of meningitis, diabetes insipidus, cerebrospinal fluid leak, epistaxis, hypopituitarism and the length of the operation.
We reviewed more than 1,900 patients who underwent pituitary adenoma surgery; however, only 1% had SPADSD. These are similar to other tumors in terms of appearance and surgical approaches. We think it important to put forward this concept. Because the bone window of the surgical approach is wider than that of other pituitary adenomas, and even need to be ground above the saddle nodule position, otherwise, the suprasellar tumor will not be removed effectively. If the Sellar diaphragm exists, part of the suprasellar tumor might fall into the Sellar after resection of the intrasellar tumor. Unfortunately, there is no such one. So it was different and more difficult at the beginning of the surgery. Since there is no Sellar diaphragmatic septum during the operation, special attention should be paid to the protection of the anterior communicating artery and optic nerve. It is a kind of tumor with histological features of pituitary adenomas and similar to endoscopic surgery for craniopharyngiomas. The nature of the tumor has a decisive influence on the choice of access to the procedure, the degree of resection during surgery, and the degree of retention of important structures during the procedure. Therefore, it is important to understand the characteristics of the tumor as much as possible before surgery, because this plays an important role in the treatment of the disease.