[Neuroimaging of idiopathic normal pressure hydrocephalus--current concepts].

Neuroimaging plays an important role in the diagnosis and management of the idiopathic normal pressure hydrocephalus (iNPH). In addition to a ventricular dilatation with an Evans index of 0.3 or more, a tightness of the subarachnoid space in the high convexity/midline areas with a concurrent dilatation of the sylvian fissure and basal cistern is characteristic in iNPH. Voxel-based morphometry techniques can readily determine the validity of these findings. Periventricular hyperintensity, marked flow void in the aqueduct, and ventricular reflux and stasis of contrast agents are believed to have limited advantages in differential diagnosis and patient management. Cerebral blood flow measurement may help in discriminating iNPH from other disorders; however, partial volume effects due to disproportionate narrowing and dilatation of the subarachnoid space can cause substantial errors during post-processing and interpretation.