Occipital hypoperfusion on SPECT in dementia with Lewy bodies but not AD

Objective: To compare regional cerebral blood flow (rCBF) changes using Tc- 99m-hexamethylpropyleneamine oxime (Tc-99m-HMPAO) SPECT in subjects with de mentia with Lewy bodies (DLB) and AD and in normal age-matched control subj ects; to examine the utility of SPECT changes in the differential diagnosis of AD and DLB. Method: Whole-brain SPECT scans were acquired using a singl e-headed rotating gamma camera (IGE CamStar XR/T) in elderly subjects with consensus criteria DLB (n = 23; mean age = 79.4 years), National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association AD (n = 50; 81.9 years), and normal contr ol subjects (n = 20; 78.1 years) after injection with 500 MBq of Tc-99m-HMP AO. Region-of-interest analysis was performed using a SPECT template regist ered in Talairach space, with rCBF normalized to cerebellum. Results: Both DLB and AD subjects had significantly reduced rCBF in parietal and temporal regions compared with the control subjects. The AD group also showed a sig nificant reduction in rCBF in the frontal and medial temporal regions and t he DLB in the occipital areas compared with control subjects. AD and DLB gr oups differed only in occipital perfusion (p < 0.01). SPECT measures (occip ital and medial temporal) correctly classified 69% of all subjects, with a 65% sensitivity and 87% specificity for DLB against AD and control subjects . Conclusion: Temporoparietal hypoperfusion on SPECT is common to both AD a nd DLB. Occipital hypoperfusion is more frequently seen in DLB. Although no t diagnostically specific in individual cases, occipital hypoperfusion on S PECT should raise suspicion that DLB may be the cause of dementia, promptin g careful search for other features of the disorder.