Hydranencephaly (HE) is a rare, mostly isolated abnormality, which is reported to affect about 1 of 5000 continuing pregnancies [1, 2]. It is one of the most severe forms of bilateral cerebral cortical anomalies. In this condition, the cerebral hemispheres are completely or almost completely missing. In their place, there is a membranous sac filled with cerebrospinal fluid (CSF), glial tissue, and ependyma. There is, however, preservation of the skull. There is variable and partial involvement of the frontal, parietal, temporal, and occipital lobes. The mesencephalon, cerebellum, thalami, basal nuclei, and choroid plexus are usually not involved [3–5]. The etiopathogenesis of HE is still unknown; however, most researchers support the hypothesis that the brain damage in HE is related to early internal carotid artery involvement [6–8]. Unlike the unilateral form, the prognosis of HE is usually quite poor. Affected patients mostly die in utero. In the survivors, death usually occurs in the first year of life. Developmental delay, drug-resistant seizures, spastic diplegia, severe growth failure, and respiratory infections are features that burden the life of these patients and are frequent causes of their death. However, patients with survivals of 20 [9], 22 [10], and 32 [7] years have been reported in the literature. The survival of the patient is related to the integrity of the brainstem, which regulates vital aspects, such as temperature, blood pressure, and cardiorespiratory function [6]. For the child with HE who survives, there is debate as to whether or not to perform any surgical treatment, considering the severe brain impairment [11]. Classical surgical treatment consists of a shunt, which drains the CSF, reducing the cerebral tension and the progressive increase of the cerebral volume. Recently, an optional treatment has been proposed, consisting of choroid plexus coagulation (CPC) [12]. CPC stabilizes macrocephaly in approximately 40% of infants with severe congenital hydrocephalus and hydranencephaly and can be considered as an alternative to shunt placement [13]. In particular, in cases of hydranencephaly with an excellent view of the choroid plexus, the procedure had good indications for avoiding the complications associated with a shunt. Because hydranencephaly is very rare and the follow-up period is typically short due to the disease characteristics, a large number of patients and long-term follow-up are needed to determine the real effectiveness of the CPC procedure in this patient group [14]. Arachnoid collapse is a previously unreported complication of CPC treatment of hydranencephaly [15]. Figures 7.1 and 7.2 depict typical aspects of hydranencephaly on computed tomography (CT) scan and magnetic resonance imaging (MRI), and Figs. 7.3 and 7.4 show neuroendoscopic techniques. Intraoperative images are shown in Figs. 7.5, 7.6, 7.7, 7.8, 7.9, 7.10, 7.11, 7.12, 7.13, and 7.14.