Suprasellar arachnoid cysts (SACs) are benign congenital collections of cerebrospinal fluid (CSF), accounting for approximately 9% of all arachnoid cysts [1–4]. These cysts progressively enlarge from an abnormality in the interpeduncular cistern or in the membrane of Liliequist. They can be classified as communicating cysts; that is, cystic dilatations of the interpeduncular cistern, and as non-communicating intra-arachnoid cysts of the diencephalic portion of the membrane of Liliequist [5]. In communicating cysts, the basilar artery bifurcation is located inside the cyst with no overlying membrane, whereas in a non-communicating cyst, the basilar artery and its branches are pushed posteriorly against the brainstem, and the cyst can be observed through a transparent membrane (diencephalic portion of the membrane of Liliequist). A new recent classification divides SACs into three types: SAC-1, SAC-2, and SAC-3. SAC-1 may arise from an expansion of the diencephalic portion of the membrane of Liliequist. SAC-2 shows a dilatation of the interpeduncular cistern and corresponds to a defect of the mesencephalic portion of the membrane of Liliequist. SAC-3 is an asymmetrical form that expands to other subarachnoid spaces [6]. However, even on a high-definition intraoperative view it can be difficult to distinguish these types of SACs, because the diencephalic portion of the membrane of Liliequist is very thin and transparent. Due to this difficulty this classification is not applied to the intraoperative images shown here.

Endoscopic neurosurgery is the best surgical approach for SACs [7], being performed mainly in patients with associated hydrocephalus. At present, there are two main types of endoscopic surgical procedures: ventriculocystostomy (VC), in which the goal is to establish communication between the cyst cavity and the ventricles, and ventriculocystocisternostomy (VCC), in which the goal is to open the cyst into both the ventricles and cisterns. There are other reports concerning different endoscopic approaches [8, 9]. Currently, the main controversy is about whether VCC is preferable to VC alone. The two procedures, VC and VCC, have proven to be almost equally effective both clinically and radiologically. Nevertheless, because of the statistically significant difference between the incidences of recurrence after VC and VCC during long-term follow-up, it has been concluded that VCC should be considered as the procedure of choice in the treatment of SACs [10]. Crimmins et al. reported on seven patients treated with VC and 13 patients treated with VCC. They found that VCC had a higher success rate, although the difference was not statistically significant, but they also found that the failure rate of VC was higher than that of VCC [11]. VCC is an effective and durable treatment for symptomatic SACs in most cases [12]. In a metareview of 23 series reported after 1980, of 176 patients with SACs treated by different surgical procedures, the endoscopic procedure was VC in 49 patients and VCC in 53. The rate of clinical-radiological improvement was higher after VCC (94.3%) than after VC (85.7%) [13]. In another review, VCC was also more frequently effective (48 of 50) than VC (18 of 21) [14]. There are two explanations for this result: First, the superior fenestration tends to close, regardless of whether a single or dual fenestration is performed, because stretching of the third ventricle creates excess tissue that can overlap and seal the fenestration after the operation. The persistence of the basal opening, even in the face of secondary closure of the apical fenestration, allows adequate cyst decompression into the basal cisterns, thus decreasing the risk of recurrence [15]. Second, chronic mesencephalon compression by the cyst may lead to secondary aqueductal occlusion. In this scenario, apical membrane fenestration alone, although allowing for adequate cyst decompression, may not result in extraventricular CSF flow [14]. In a recent study it was concluded that VCC was superior and that the postoperative radiological examinations must reveal the adequacy of fenestrations and flow through fenestration sites, reduction of the cyst and ventricle size, and reorientation of the chiasm and mammillary bodies to an acceptable anatomical position [16]. Therefore, endoscopic VCC should be performed as the first surgical procedure in all patients with SAC and hydrocephalus. Patients who do not improve after the VCC procedure may be treated with a shunt [14]. In SAC patients without hydrocephalus, endoscopic VCC can be performed as an effective, safe, and simple treatment option by using intraoperative image-based neuronavigation. The image-guided neuroendoscopic procedure improved the accuracy of the endoscopic approach and minimized brain trauma [17]. Also, virtual endoscopy could be an interesting option for surgical planning [18]. Figures 6.1 and 6.2 depict typical aspects of SAC on magnetic resonance imaging (MRI). Intraoperative images are shown in Figs. 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 6.10, 6.11, 6.12, 6.13, 6.14, 6.15, 6.16, 6.17, 6.18, 6.19, 6.20, 6.21, 6.22, 6.23, 6.24, 6.25, 6.26, 6.27, 6.28, 6.29, 6.30, 6.31, 6.32, 6.33, 6.34, and 6.35.