PURPOSE: Loculated hydrocephalus is a condition in which discrete fluid-filled compartments form in or in relation to the ventricular system of the brain. Both uni- and multiloculated variants exist, with marked differences in outcome. However, several competing and seemingly interchangeable nomenclatures exist, and none address the pathophysiological basis of the condition. To clarify current treatment options, we carried out a review of the literature. METHODS: A protocol describing search strategy and inclusion criteria was prepared in advance, and a search of MEDLINE, the Cochrane Database of Systematic Reviews, and the U.S. NIH ClinicalTrials.gov database was carried out with the search terms: "multicystic," "multiloculated," "multicompartment," "uniloculated," and "loculated." All were used in conjunction with the search term "hydrocephalus." RESULTS: A single study with a control group was found. Remaining reports are purely case series. Research efforts are hampered by unclear and seemingly interchangeable nomenclatures, which makes comparison between studies difficult. There is a paucity of studies of high methodological quality concerning choice of treatment. At the case series level, evidence is in favor of the neuroendoscopic approach. CONCLUSIONS: In order to ensure a consistent nomenclature as well as to guide future research, we propose a new system of classification for loculated hydrocephalus. It acknowledges the differences between uniloculated and multiloculated hydrocephalus, and goes beyond a pure anatomical model. For future research, it enables us to clearly characterize subgroups, which is essential if we are to advance our understanding and level of care for this challenging group of patients.