Cognitive deficits of pure subcortical vascular dementia vs. Alzheimer disease: PiB-PET-based study.

OBJECTIVES

Despite many neuropsychological studies to differentiate subcortical vascular dementia (SVaD) from Alzheimer disease (AD), previous studies did not eliminate confounding effects of mixed Alzheimer and vascular pathology. We aimed to investigate neuropsychological differences between patients with Pittsburgh compound B (PiB)-negative SVaD and those with PiB-positive AD.

METHODS

We recruited patients who were clinically diagnosed with SVaD or AD and underwent an 11C-PiB-PET scan. All patients with SVaD fulfilled DSM-IV criteria for vascular dementia and had severe white matter hyperintensities. The diagnosis of AD was made on the basis of criteria for probable AD proposed by the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association.

RESULTS

The final patient sample consisted of 44/67 (65.7%) patients with SVaD who tested negative for PiB retention [PiB- SVaD] and 61/68 (89.7%) patients with AD who tested positive for PiB retention [PiB(+) AD]. Patients with PiB- SVaD performed better than patients with PiB(+) AD on both verbal and visual memory tests including delayed recalls of the Seoul verbal learning test and Rey complex figure test. Patients with PiB- SVaD were worse than patients with PiB(+) AD on phonemic fluency of the Controlled Oral Word Association Test and Stroop color test.

CONCLUSIONS

Patients with PiB- SVaD were better at memory but worse at frontal function than patients with PiB(+) AD. The differences in memory/frontal functions observed between the 2 groups, however, could not differentiate all individual data due to some overlap in the cutoff threshold.