Differentiating Alzheimer's disease from vascular dementia — clinical, neuroimaging, and biomarker approach

A 74-year-old hypertensive male presents with a 2-year history of progressive cognitive decline. His deficits began abruptly after a lacunar infarct and have progressed in a stepwise pattern. MRI shows periventricular white matter changes and bilateral lacunar infarcts. How do we differentiate vascular dementia from Alzheimer's disease clinically and on neuroimaging? What is the role of CSF amyloid/tau and amyloid PET in atypical presentations? Are acetylcholinesterase inhibitors beneficial in VaD?