Alzheimers disease and cerebral small vessel disease have a considerably overlap in patients and have common risk factors. The diseases are difficult to separate in individual patients and we hypothesize that a reduced cerebral vascular reserve may be a measurement of small vessel disease independent of Alzheimers disease.

Patients with presumed Alzheimers disease (n=20), cerebral small vessel disease (n=20) and healthy age-matched subjects (n=15) are examined with quantitative [15O]H2O positron emission tomography (PET) for measurements of brain perfusion before and after diamox infusion that dilates cerebral vessels. Additional [15O]H2O PET scans of the heart allows for a non-invasive input function so the cerebral vascular reserve can be measured quantitatively.

Alzheimers disease and cerebral small vessel disease are increasingly common in the elderly population and constitute around 90% of new dementia cases in Denmark. The diseases have a considerably overlap in patients and have common risk factors. The cause of dementia can be difficult to separate in individual patients but a reduced cerebral vascular reserve may be a measurement of small vessel disease independent of Alzheimers disease. We hypothesized that patient with small vessel disease have reduced increase in brain perfusion after medical brain vessel dilatation. While Alzheimer patients may have reduced perfusion in rest but normal increase after medical brain vessel dilatation as compared to healthy subjects.

Patients with presumed Alzheimers disease (n=20), cerebral small vessel disease (n=20) and healthy age-matched subjects (n=15) are examined with quantitative [15O]H2O PET for measurements of brain perfusion before and after diamox infusion that dilates cerebral vessels. Additional [15O]H2O PET scans of the heart allows for a non-invasive input function so the cerebral vascular reserve can be measured quantitatively.

Inclusion Criteria:

• presumed Alzheimer's Disease (group 1)
• diagnosed with small vessel disease of the brain by MRI and presumed cognitive dysfunction (group 2)

Exclusion Criteria:

• major claustrophobia
• major psychiatric diseases
• other major somatic diseases
• allergy to diamox

Recruited from Department of Neurology, and Department of Geriatric and Palliative Medicine at Bispebjerg Hospital, Copenhagen, Denmark.

Healthy subjects are recruited from internet advertisments.

Data will be available at reasonable request following Danish laws on personal data regulations.