Cobalt-55 positron emission tomography in vascular dementia: significance of white matter changes

Background: Vascular dementia (VaD) is still used as a covering term to indicate the relationship between cerebrovascular disease and the progressive cognitive disorder. The contribution of white matter changes (WMCs), seen with computed tomography (CT) and magnetic resonance imaging (MRI) of the brain, to dementia had not been fully elucidated. Cobalt-55 (Co-55) positron emission tomography (PET) allows us to distinguish between recent and old infarcts. Purpose: The present study investigates whether Co-55 PET can detect the lesions responsible for the progression of the cognitive disorder in VaD patients. Patients and methods: 20 consecutive patients with a previous history of repeated strokes occurring more than 6 months before and with multiple cortical infarcts, lacunes and WMCs on CT and 5 age-matched controls were investigated with Co-55 PET. The stroke patients were divided in two groups 8 with and 12 without VaD. Average Co-55 counts in cerebral cortex, deep gray nuclei and white matter were compared to the value in the cerebellum used as reference. Results: In the control group, the Co-55 uptake was identical in the cerebral cortex and in the cerebellum, but lower in the deep gray nuclei and the cerebral white matter. When comparing the stroke groups with the control, the Co-55 uptake was similar for the cerebral cortex and deep gray nuclei, but significantly increased in the cerebral white matter. The Co-55 uptake was also more increased in the stroke group with VaD compared to the non-demented group. Conclusion: Co-55 PET shows that the WMCs are due to the ongoing damage of probably ischaemic origin which is more prominent in stroke patients with progressive cognitive decline. (C) 2001 Elsevier Science B.V. All rights reserved.