Positron emission tomography with [18F]fluorodeoxyglucose differentiates normal pressure hydrocephalus from Alzheimer-type dementia.

Because diagnostic criteria for normal pressure hydrocephalus have not been clearly determined, it is often difficult to differentiate patients with this potentially treatable condition from those with Alzheimer-type dementia. We have studied three patients with normal pressure hydrocephalus, 17 patients with Alzheimer-type dementia, and seven healthy elderly controls using positron emission tomography and [18F]Fluorodeoxyglucose (FDG). Both Alzheimer-type dementia and normal pressure hydrocephalus groups showed lower cortical rates of FDG utilisation than controls. However, the patterns of metabolic abnormality were distinctly different in the two dementia groups, with Alzheimer-type dementia subjects demonstrating bilateral temporoparietal hypometabolism while normal pressure hydrocephalus subjects showed globally diminished glucose use.