—We agree with Dr Haan and colleagues that single proton emission computed tomography (SPECT) brain imaging should not be used to estimate dementia severity in Alzheimer's disease (AD). Dementia is a clinical diagnosis, and clinical assessments, including cognitive tests, are the appropriate way to measure dementia severity. Our report1 indicated that widespread decreases in cerebral perfusion, especially in the parietal region, were characteristic biological correlates of AD. Despite this association, we noted that iofetamine hydrochloride I123 (IMP) SPECT may be limited in supporting the diagnosis of AD and judging dementia severity because of modest sensitivity and specificity. This latter conclusion must be amended somewhat in light of new data. We have extended IMP SPECT studies to include 58 patients with probable AD, and have confirmed our initial findings: cerebral perfusion is decreased in AD across all stages of dementia; the greatest decrements in perfusion are in the parietal regions; and
Johnson KA, Holman BL, Rosen TJ, Nagel JS, Growdon JH. Single Photon Emission Computed Tomography in Alzheimer's Disease-Reply. Arch Neurol. 1989;46(11):1166. doi:https://doi.org/10.1001/archneur.1989.00520470016010
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