Calcifying pseudoneoplasm of the neuraxis (CAPNON) in the posterior third ventricle – a challenge for neuroendoscopy.

We report the first case of a purely intraventricular CAPNON in the posterior third ventricle. When encountering such 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 to typical soft tumors should be assumed. As data on intraventricular CAPNON is very limited, no assumptions regarding natural history can be made. However, biopsy of the lesion and treatment of associated hydrocephalus appear to be the primary neurosurgical goals, followed by imaging surveillance.