Is memory loss from dementia caused by multiple mini strokes different from the type caused by alzheimer's? in what way?

Yes & no: Memory loss is memory loss, no matter how you lose it. However, it also depends upon what memory is lost. Vascular dementia or memory loss from many strokes is described as step-wise in progression. It might be possible to slow down by optimize risk factors. Alzheimer's disease is a slow inexorable slide or loss of memory once it begins altho we can try to minimize initial risk via exercise & food.

Pattern different: "vascular dementia" is associated with heart disease, hypertension, high cholesterol, is rather abrupt, stepwise, and associated with some focal outcomes. The cognitive exam is perhaps similar to alzheimer;s, but abrupt changes not seen in alzheimer's.