People with Lewy body disease may experience large fluctuations in attention and thinking. They can go from almost normal performance to severe confusion within short periods. Visual hallucinations are also a common symptom. Three overlapping disorders can be included with Lewy body disease:
• Dementia with Lewy bodies
• Parkinson's disease
• Parkinson's disease dementia
When movement symptoms appear first, Parkinson's disease is diagnosed. As Parkinson's disease progresses most people develop dementia. When cognitive symptoms appear first, this is diagnosed as dementia with Lewy bodies. Lewy body disease sometimes co-occurs with Alzheimer's disease and/or vascular dementia.