OBJECTIVE

The authors describe a patient in whom neuroimaging using Tc-99m HMPAO SPECT, F-18 fluorodeoxyglucose (F-18 FDG) coincidence imaging, and magnetic resonance imaging (MRI) identified an anterior choroidal artery infarction. Neuroimaging played a critical role in confirming this diagnosis, because the patient had symptoms of progressive cognitive decline and satisfied the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for Alzheimer's disease (AD).

METHODS

Tc-99m HMPAO brain SPECT was performed using a triple-head gamma camera. F-18 FDG scanning was obtained 40 minutes after intravenous injection of 5 mCi F-18 FDG using a coincidence camera. A brain MRI scan was performed using a 1.5-Tesla scanner.

RESULTS

Tc-99m HMPAO SPECT showed focal hypoperfusion to the right parahippocampal cortex. F-18 FDG coincidence imaging showed a more extensive reduction in glucose metabolism compared with SPECT. The MRI scan confirmed the presence of a small segmental choroidal artery infarction. The Tc-99m HMPAO and F-18 FDG scans were not consistent with AD.

CONCLUSIONS

This case illustrates the value of the regional cerebral blood flow SPECT for evaluating memory impairment in the elderly. Decreased regional cerebral blood flow to the posterior temporoparietal region is consistent with AD, whereas regional cerebral blood flow diminution in a vascular territory is consistent with vascular dementia. In this case, the patient was clinically diagnosed with AD, and SPECT was performed to establish the baseline regional cerebral blood flow before the cholinesterase inhibitor donepezil was administered. An infarction was diagnosed on the regional cerebral blood flow brain SPECT scan, which was later confirmed by MRI. Infarctions of the parahippocampal cortex may resuft in memory impairment, which can appear clinically similar to AD.