Brain blood flow in the dementias: SPECT with histopathologic correlation in 54 patients.

Purpose: To evaluate single photon emission computed tomographic (SPECT) imaging of regional cerebral blood flow in the diagnosis of Alzheimer disease (AD) and the differential diagnosis of the dementias.
Materials and Methods: Regional cerebral blood flow SPECT was performed with inhaled xenon-133 in 261 patients and with injected technetium-99m hexamethyl-propyleneamine oxime (HMPAO) in 162 patients with possible dementia. In 16 patients, both agents were used in 1 day. SPECT images obtained in elderly healthy control subjects (with Xe-133 in 15, with Tc-99m HMPAO in 14) were available. In each patient without AD, further classification of disease was attempted. Histopathologic correlation was available in 54 patients (with autopsy in 51, with biopsy in three).
Results: SPECT diagnoses were true-positive in 37, true-negative in eight, false-positive in three, and false-negative in six patients. Sensitivity was 86% (37 of 43; 95% confidence limits = .72, .95); specificity, 73% (eight of 11; confidence limits = .39, .94); positive predictive value, 92% (37 of 40; confidence limits = .80, .98); and negative predictive value, 57% (eight of 14; confidence limits = .29, .82).
Conclusion: Regional cerebral blood flow SPECT may assist in the early and late diagnoses of AD and in the differential-diagnosis of the dementias when there is a complicated or confusing clinical picture.