Everyday Health had an article about the causes of dementia. "Dementia is really a big umbrella term that covers a number of different conditions that cause dementia symptoms."
“There are many different types of dementia,” says Ross Andel, PhD, associate professor at the School of Aging Studies at the University of South Florida in Tampa. “The most common types of dementia are Alzheimer’s disease, vascular dementia, Lewy body dementia, and Parkinson’s disease. All types of dementia are characterized by abnormal neurodegeneration, that is, brain cells dying off in high numbers daily. In most cases, this leads to cognitive and behavioral deficits or, in Parkinson’s disease, to deficits in motor skills.”
Cortical dementia is likely to result in dementia symptoms such as loss of memory, loss of the ability to recognize people, and difficulty recalling the right words for things or concepts. Cortical dementias include:
Alzheimer’s disease. Alzheimer’s disease causes a loss of memory and ability to think clearly and typically leads to loss of ability to complete tasks of daily living.
Frontotemporal dementia. This type of dementia results from degeneration of cells in the frontal lobe; it’s characterized by behavioral and language deficits at a relatively young age — as young as 40.
Wernicke-Korsakoff syndrome. This type of dementia is due to a deficiency in thiamine (vitamin B1) but is also often related to a history of heavy alcohol consumption or to having AIDS, or acquired immunodeficiency syndrome.
Dementia symptoms associated with subcortical dementias include loss of motor skills and the ability to learn processes, resulting in a general sense of slowing down. These types of dementia include:
Huntington’s disease. A rare, inherited cause of dementia, Huntington’s disease leads to problems with motion such as twitches and lack of balance or coordination and may also lead to changes in mood, personality, and behavior.
Parkinson’s disease. Parkinson’s disease is characterized by the gradual loss of motor skills, or shakiness and tremors while in motion. People with Parkinson’s disease may eventually experience other dementia symptoms, such as loss of memory.
Vascular dementia. Vascular dementia occurs as the result of loss of oxygenated blood to parts of the brain. This can be the result of a single stroke or many small strokes, in which case it is called multi-infarct dementia. Evidence shows that subcortical vascular dementia also has effects in the cortex, leading to cortical dementia symptoms.
Some types of dementia appear to affect both cortical and subcortical areas of the brain such as Dementia with Lewy bodies. This type of dementia occurs because clusters of a certain type of protein called alpha-synuclein form in the neurons in various areas of the brain, leading to impaired memory, motor skills, and mood.