Calcifying Pseudoneoplasm of Neuraxis (CAPNON) in the Posterior Third Ventricle—Challenge for Neuroendoscopy

Background We report the first case of a purely intraventricular calcifying pseudoneoplasm of neuraxis (CAPNON) in the posterior third ventricle. Case Description A 63-year-old male without any previous medical history presented with Hakim triad. Imaging showed a calcified lesion of the posterior third ventricle with hydrocephalus. An endoscopic third ventriculostomy was performed. Endoscopic removal or debulking of the lesion was impossible due to its rock-hard consistency, and thus the procedure was aborted after biopsy. Conclusions When encountering such calcified lesions within the ventricular system, especially in proximity to eloquent regions, the decision making process should include the hard consistency and parenchymal adhesions as obstacles to neuroendoscopic removal. Even for biopsy, a higher morbidity rate compared with typical soft tumors should be assumed. Although data on intraventricular CAPNON is limited, biopsy of the lesion and treatment of associated hydrocephalus appear to be the primary neurosurgical goals, followed by imaging surveillance.