How do i know if it is vascular dementia or something else?

Can be hard to know: If dementia occurs in the context of cerebrovascular disease (strokes, tias), especially if the deficits correlate with known anatomical lesions, it is presumed vascular. Neuropsych testing may add evidence (or not). Vascular dementia also tends to progress in discrete steps, rather than continuously. There are many causes of dementia; some can be hard to diagnose in the living patient.

May need expert: For a specific diagnosis, it is best to see someone experienced with that type of illness. A geriatric psychiatrist or a neurologist experienced with dementia may be the best person or you can check with the person's primary care provider.