The symptoms of normal-pressure hydrocephalus are very similar to Alzheimer’s disease. When identified as a distinct disease it is known as the “wet, wild, and wobbly.” Characterized by urinary incontinence (wet), dementia (wild), and gait dysfunction (wobbly). It is estimated that 1.6–5.4% of those with dementia are affected by iNPH. If the condition is left untreated—most of these cases are overlooked as Alzheimer’s disease—chronic iNPH patients share overlapping characteristics with Alzheimer’s disease in 75% of the time. It becomes increasingly difficult to differentiate the two the longer that iNPH is left untreated since the NPH syndrome will become Alzheimer’s disease.
Although there is no community-wide study looking at how common NPH is, there are some small sample studies that indicates that it is likely to be very common among older adults 65 years older.  Among older adults in the community, the prevalence is around 1.3%, higher in assisted-living and extended-care residents with 11.6%. A small proportion of patients (2%) show permanent improvement after releasing the pressure in the brain using a shunt. The problem is that there are no easy indicators—including brain imaging—for distinguishing iNPH and Alzheimer’s disease. The images must still be interpreted with clinical features, blood measurements, CSF biomarker measurements, tap test, and CSF drainage results.
Because it is hard to diagnose, iNPH remains under recorded. Many studies report an association between hypertension, vascular disease and iNPH—with strokes and heart attacks being common precursors—so there is a need to look at any vascular disease as a precursor to Alzheimer’s. And the problem is that Alzheimer’s disease is so broad a category that most things that affect the brain and cause behavior changes are likely to be diagnosed Alzheimer’s disease even though it is likely not, such as amyloid deposition, CSF biomarker content, and presence of vasculature diseases.  A diagnosis of Alzheimer’s disease is a prescription for lost hope, whereas vascular disease is more likely to be amenable to therapy.
Vascular dementia—where the plaques and tangles are caused by a lack of blood flow in the brain (called cerebral perfusion)—is confused with Alzheimer’s disease most often because both share the same biomarkers and have the same expression. They look the same to the inexperienced clinician. Cerebrovascular disease among adults over 75 years of age is a common condition—36 percent overall, 25 percent for coronary, 58 percent hypertension, and 11 percent for stroke.  It seems likely that because of these co-morbidities, vascular dementia contributes to, and is sometimes mis-diagnosed as Alzheimer’s disease. The silent issue is recognizing how frequently vascular disease promotes dementia. Contemporary neuroscience still lacks a thorough understanding of exactly what contribution cerebrovascular disease makes to cognitive impairment. 
The answer is to move away from the practice of calling anything that disturbs cognition as Alzheimer’s disease. Clinicians need a strategy, a roadmap to differentiate all these different type of diseases because they have different causes. Knowing the cause is the first step to formulating a cure. That is, if we are truly serious about finding a cure for Alzheimer’s disease.
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