Clinical and Radiological Evolution of Idiopathic Normal Pressure Hydrocephalus: A Critical Review

The pathophysiology of idiopathic normal pressure hydrocephalus (iNPH) remains poorly understood. While it is commonly accepted that iNPH has an insidious onset, little is known about its preclinical and early stages and its development over time.

To gain more insight into how iNPH becomes manifest clinically and radiologically, and how its major clinical symptoms evolve in non-shunted patients.

For this critical review a literature search was performed using specific search terms concerning the evolution of iNPH. Manuscripts were categorized according to their content providing information on different domains including the early manifestation of clinical features, the evolution of the three major clinical symptoms, and the development of radiological findings.

Gait disturbance in general, is the earliest clinical symptom of iNPH. There is a gradual but variable decline within the first years resulting in a change of phenotype. Cognitive impairment varies widely depending on co-morbidities. Urinary dysfunction evolves from urinary urgency to incontinence. Radiological features of iNPH such as ventricular enlargement, enlarged subarachnoid spaces, and flattening of sulci at the parasagittal high convexity are present in the preclinical stage of iNPH, but the sequence of their appearance remains unclear as well as the impact of white matter lesions.

The evolution of iNPH shows remarkable heterogeneity. While there is a need to define distinct clinical stages, it is also important to better identify the preclinical stages of iNPH. Assessment of treatment outcomes needs to consider the stage of the disease at the time of intervention.