Parkinsonism in idiopathic normal pressure hydrocephalus: is it time for defining a clinical tetrad?

BACKGROUND: Association between parkinsonism and idiopathic normal pressure hydrocephalus (iNPH) still remains debated. There is already plenty of evidences in the literature suggesting that this clinical sign can be considered as an integral part of the clinical spectrum of iNPH patients. METHODS: We reviewed the possible pitfalls in the core clinical definition of iNPH based on available international diagnostic criteria, phenomenology of parkinsonism in iNPH, and neuroimaging supporting the presence of parkinsonism in iNPH. CONCLUSIONS: We argue that the diagnostic definition of the iNPH “triad” should be possibly reconsidered as a “tetrad” also including parkinsonism.