There are numerous causes of the symptoms of dementia. Dementia is not a single disease but a syndrome caused by different diseases and conditions that damage the brain. The most common causes include Alzheimer's disease, vascular dementia, dementia with Lewy bodies, frontotemporal dementia, and Parkinson's disease. Other causes can include Huntington's disease, brain injuries, infections like HIV/AIDS or syphilis, multiple sclerosis, progressive supranuclear palsy, chronic alcohol abuse, brain tumors, vitamin deficiencies, and certain medications. Altogether, there are at least dozens of different diseases and conditions known to cause dementia symptoms, with the main categories including:

• Neurodegenerative diseases like Alzheimer's and Parkinson's
• Vascular conditions affecting brain blood flow
• Infections affecting brain function
• Brain injuries or trauma
• Toxic exposures and nutritional deficiencies
• Rare genetic or autoimmune disorders

The exact number of causes can vary depending on classification, but there are many distinct underlying causes recognized in medical literature that can produce dementia symptoms.