The symptoms of idiopathic normal pressure hydrocephalus (iNPH) are generally seen in aged, and iNPH has been overlooked or misdiagnosed. In Japan, since the Clinical Guidelines were published, remarkable progress are noted in the recognition of it and clinical researches for it. In this paper, recent progress diagnostic measures for iNPH is discussed, focusing on the key role of clinical features, neuroimagings, and tap test. As for clinical symptoms, in particular the distinctive features of cognitive and behavioral symptoms have been delineated. The clinical significance of MRI features of iNPH, i.e., ventriculomegary with tight high convexty/midline subarachnoid spaces and enlarged Sylvian fissures, have been validated in a prospective cohort study, Study of Idiopathic Normal Pressure Hydrocephalus on Neurological Improvement (SINPHONI). Disproportionately enlarged sub arachnoid-space hydrocephalus (DESH) has been proposed to designate iNPH with these MRI features consisting of a major proportion of iNPH. Although tap test is useful in diagnosis and in making decision of shunt surgery, the results of SINPHONI suggest that its procedure needs to be refined to increase the diagnostic accuracy.
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