Other medical conditions listed in the Disease Database as possible causes of Dementia as a symptom include: 1  Alpers disease. 2  Aluminium (dialysis related) toxicity. 3  Alzheimer's disease. 4  Amyloidosis. 5  Amyotrophic lateral sclerosis-parkinsonism dementia complex of Guam. 6  CADASIL. 7  Cerebral amyloid angiopathy.