Imaging Perspectives on Hydrocephalus: CSF Flow, Glymphatic Function, and Clinical Implications in the Diagnosis and Management of Normal Pressure Hydrocephalus.

Hydrocephalus is defined by abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles, resulting in ventriculomegaly with variable effects on intracranial pressure. Historically classified as obstructive or communicating, contemporary frameworks further categorize hydrocephalus by chronicity, age of onset, and etiology, particularly distinguishing idiopathic from secondary causes in adults. Hydrocephalus most commonly arises from impaired CSF circulation or absorption, with less frequent contribution from altered CSF production. Increasing attention has been directed toward alternative CSF clearance mechanisms, including the glymphatic system, which remain incompletely defined. Radiologic evaluation is central to the diagnosis and management of hydrocephalus, enabling accurate assessment of ventricular morphology, associated parenchymal changes, and potential underlying etiologies. Normal pressure hydrocephalus, a chronic communicating hydrocephalus of older adults, is characterized by a clinical triad of gait disturbance, cognitive decline, and urinary dysfunction. Conventional structural and advanced imaging markers may assist in diagnosis, prognostication, and selection of patients for CSF diversion, in conjunction with clinical assessment. This review summarizes fundamental physiologic concepts of CSF dynamics and imaging features of hydrocephalus, with particular emphasis on imaging in normal pressure hydrocephalus.