THE VALUE OF HMPAO SPECT SCANNING IN THE DIAGNOSIS OF EARLY ALZHEIMERS-DISEASE IN PATIENTS ATTENDING A MEMORY CLINIC

The value of hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomograpy (SPECT) as a diagnostic test for Alzheimer's disease (AD) was assessed in 44 patients attending a Memory Clinic. A comprehensive physical and psychiatric examination and detailed neuropsychological tests were used to arrive at a clinical diagnosis, in accordance with NINCDS-ADRDA criteria. The mean patient age was 69 (range 59-84) years, and the mean score on the Mini-Mental State Examination (MMSE) was 24 (range 7-30). Of 26 patients with a clinical diagnosis of AD, only 15 demonstrated a scan pattern strongly suggestive of AD. Four scans were normal, four showed evidence of ischaemic change and three were in the category 'other', one of which showed bilateral frontal hypoperfusion, but normal temporoparietal flow. Of the eight patients considered by clinical criteria to be non-demented, no scan showed an AD pattern, but three showed an ischaemic pattern. Both of the patients diagnosed clinically as suffering from multi-infarct dementia showed SPECT scan evidence of ischaemic change. Of the remaining eight patients with other clinical diagnoses only one scan suggested AD. We conclude that the HMPAO SPECT scan appearances which arise from AD in the early stages of the disease do not on their own allow the disease to be accurately diagnosed, but they may be useful if interpreted in conjunction with other imaging techniques.