Craniopharyngioma is a rare embryonic malformation arising from the squamous epithelial remnants of Rathke’s pouch. A bimodal distribution by age has been found, with peak incidence rates in children from 5–14 years of age and in older adults from 50–74 years of age[2].
There are many ways to classify craniopharyngiomas. In terms of location, they can be divided into three types based on their relationship to the sellar region: 1) suprasellar craniopharyngiomas, 2) intra- and suprasellar craniopharyngiomas, and 3) purely intrasellar craniopharyngiomas[6]. Infradiaphragmatic craniopharyngiomas are relatively rare compared with the supradiaphragmatic type and account for approximately 5% of patients[7]. In this study, nine patients were purely intrasellar craniopharyngiomas, and the rest were intrasuprasellar craniopharyngiomas. When the tumor invades and gradually impinges on the sellar region, patients develop visual disorders. Infradiaphragmatic craniopharyngiomas can induce more severe symptoms compared with supradiaphragmatic craniopharyngiomas, including signs of endocrine dysfunction and visual disturbances, because of the compression of the pituitary gland and surrounding structures. Pathologically, there are two main types of craniopharyngiomas: adamantinomatous and papillary. The former usually occur in children and are accompanied by calcifications. The latter are more likely to appear in adults[2, 6]. In childhood and adolescents, adamantinomatous craniopharyngiomas with cyst formation are more common.
Obtaining a definitive diagnosis for cystic lesions in the sellar region is difficult and the diagnosis can only be confirmed by pathological exam during and after the procedure. However, craniopharyngiomas cannot be ruled out as the potential cause of hyperintensity in a T1-weighted (T1WI) MRI. A craniopharyngioma typically appears as a solid-cystic lobulated lesion with reticular enhancement of the solid portion on an MRI [8]. Cystic infradiaphragmatic craniopharyngiomas, which are relatively rare, often manifest as homogeneous, high signal intensity lesions on T1WI without enhancement, and the signal intensity is similar with T1WI contrast enhancement scans[7]. Cystic infradiaphragmatic craniopharyngiomas are often confused with Rathke cleft cysts, pituitary apoplexy, and arachnoid cysts[9].
Transsphenoidal surgery can provide a clearer and wider vision of the surgical field with fewer complications compared with transcranial surgery[10, 11]. Wang et al. suggest that, though transsphenoidal surgery can impair the pituitary gland, it has great advantages in improving hyperprolactinemia and alleviating visual impairment and defects. At the same time, it is associated with a low recurrence rate[7]. The most popular approaches to transsphenoidal surgery are microscopic and endoscopic surgery.
Endoscopic transsphenoidal surgery has become a reliable treatment method for primary and recurrent craniopharyngiomas in the last decade[12]. For infradiaphragmatic craniopharyngiomas that originate from the pituitary stalk, endoscopic surgery is an efficient way to dissect the adhering and surrounding vital structures. According to a retrospective study of 226 patients[13], intrasellar craniopharyngiomas carry the lowest probability of hypothalamic dysfunction after radical resection compared with the other types of craniopharyngiomas. Over the last decade, neurosurgeon preference for endoscopy has increased significantly[14]. The most obvious advantage of endoscopic surgery is providing a panoramic view of the operating field with changeable angles, especially in the suprasellar area, which allows surgeons to obtain a precise view of the surrounding critical structures[5, 15, 16]. With the help of angled lens endoscopes, surgeons can even obtain direct visualization of the suprasellar region[17]. This better visualization allows the normal pituitary tissue to be more easily distinguished from the cystic walls of the tumor and better saddle diaphragm resection can be achieved without the need to blindly rely on surgeon experience. In our study, six patients underwent saddle diaphragm resection, while the remaining 14 patients were not. In terms of average GTR rate, the resection group was 100%, while the other group was 42.9% (P = 0.0419). And there was significant difference in the recurrence rate between the two groups (0% vs 57.1%, P = 0.0419). In comparison to supradiaphragmatic craniopharyngiomas, infradiaphragmatic craniopharyngiomas are very uncommon, accounting for around 5% of cases[7]. Future advancement of this study requires the evaluation of more patients.
Ogawa et al. demonstrated that pituitary function can partially recover even after pituitary stalk removal [18] and aggressive tumor removal can prevent tumor regrowth. In this study, we found the postoperative complications of the two surgical methods did not differ significantly (Table 1). Thus, as the goal is to remove as much of the tumor as possible to reduce the recurrence rate, better saddle diaphragm resection is recommended. Intraoperative CSF leakage occurred in 100% of patients in the saddle diaphragm resection group, while the rate within the saddle diaphragm preservation group was 0% (P < 0.0001). However, even if the probability of cerebrospinal fluid leakage increases, this is likely an acceptable cost given the decreased risk of tumor recurrence and that the leakage can be addressed with fascia lata, muscle, or fat implantation [19]. In addition, not all patients with cerebrospinal fluid leakage develop intracranial infections. Of the 6 patients in the saddle diaphragm resection group with cerebrospinal fluid leakage, none have progressed. According to a prospective, multicenter, controlled research study of nonfunctioning pituitary adenomas, less experienced endoscopic surgeons can surprisingly achieve similar GTR rates compared with experienced microscopic surgeons [20]. Endoscopic surgery has less of a learning curve and it is easier for less experienced surgeons to achieve good results in a shorter time. This study also found that in experienced hands, endoscopic surgery carries a low complication rate, which was consistent with our results.
If it is impossible to completely remove tumors or if gross resection may result in severe side effects, then postoperative radiation can be considered to improve the prognosis[21–24]. Recent research has proven that limited surgery and photon-based conformal radiation therapy achieve excellent tumor control[25]. For cystic craniopharyngiomas, [32P] intracavitary irradiation is recommended[26].