Diagnosis. As is the case with other types of dementia, there is not a single diagnostic test or tool. Usually, a diagnosis of Lewy body dementia comes from the expected best judgement of a doctor based on the patient’s symptoms. The most fool-proof way to diagnose beyond this is through a postmortem autopsy. However, the majority of experts can recognize the similarities between Lewy body and Parkinson’s disease and will look at the processing problems associated with similar proteins in the brain. Doctors will also be on the lookout for complications that are commonly associated with the disease. Such complications include tremors, depression, aggression, and an increased risk of falling.