Magnetic Resonance Imaging Diagnosis in Normal Pressure Hydrocephalus

Abstract

Background: Idiopatic normal pressure hydrocephalus (iNPH) is a progressive neurologic syndrome featured by the triad of gait disturbance, mental deterioration and urinary incontinence, associated with ventriculomegaly and normal cerebrospinal fluid (CSF) pressure. The clinical presentation may be atypical or incomplete, or mimicked by other diseases, so conventional neuroradiologic imaging plays an important role in defining this pathology. iNPH pathophysiologic mechanisms have not yet been fully elucidated, although several studies have demonstrated the involvement of the glymphatic system, a highly organized fluid transport system, the malfunction of which is involved in the pathogenesis of several disorders including normotensive hydrocephalus.

Methods: Recent studies have shown how crucial in the diagnosis of this pathology is the definition of morphologic biomarkers, such as ventricular enlargement disproportionate to cerebral atrophy and associated ballooning of frontal horns; periventricular hyperintensities; and corpus callosum thinning and elevation, with callosal angle <90 degrees.

Results: Another interesting feature that is becoming a well-recognized factor to look for and useful for the diagnosis of iNPH is disproportionately enlarged subarachnoid space hydrocephalus, which includes enlarged ventricles, tight high-convexity and medial surface subarachnoid spaces, and expanded Sylvian fissures. A correct choice of MRI sequences is important for a proper characterization identification of others diseases that may underlie this pathology. Magnetic resonance imaging allows us to evaluate CSF flow, enabling us to define qualitative and quantitative parameters necessary for the purpose of accurate iNPH diagnosis.

Conclusions: iNPH can represent a real diagnostic challenge; a proper correlation among clinical features, traditional MRI, and CSF dynamics analysis can lead to a correct diagnosis.

Keywords: CSF flow; Callosal angle; Evans index; Glymphatic system; MRI; Normotensive hydrocephalus.