AQP4 and Hydrocephalus: New imaging modalities and fluid biomarkers hold the promise of the earlier, more precise characterization of hydrocephalus subtypes: advanced MRI sequences such as diffusion tensor imaging and phase-contrast flow studies, when combined with cerebrospinal fluid or blood markers such as neurofilament light chain or aquaporin-4 autoantibodies, could allow for the noninvasive phenotyping and real-time monitoring of disease progression and treatment response.