How are Parkinson's disease, Alzheimer's disease, and vascular dementia different from one another?

Question

What will be an ideal response?

Answer 1

Some dementias, like Parkinson's disease, first damage the subcortical parts of the brain, areas below the cortex. These dementias are characterized by a progressive loss of motor control. Because the damage occurs first in the subcortical areas of the brain, mental abilities, which are controlled by the cortex, are not initially affected. As the disease progresses and brain deterioration spreads to include the cortex, thought and memory deficits appear.
Alzheimer's disease is characterized by widespread brain deterioration and the presence of amyloid plaques and neurofibrillary tangles in the cerebral cortex. Beta-amyloid is a protein present in the tissue that surrounds neurons in the healthy brain. Alzheimer's patients experience inflammation that causes the beta-amyloid to accumulate and join with clumps of dead neurons and glial cells, forming large masses called amyloid plaques. It is thought that amyloid plaques disrupt the structure and function of cell membranes and contribute to the formation of neurofibrillary tangles, twisted bundles of threads of a protein called tau that occur when neurons collapse. Even healthy brains have some tangles, but in cases of Alzheimer's, there is inflammation and a proliferation of plaques and tangles, as well as a progressive loss of neurons that interfere with brain functioning. Alzheimer's disease is associated with altered neurogenesis in the hippocampus, impairing the generation and development of new neurons. As neurons die, brain functioning declines. Specific patterns of cognitive and memory loss are common in Alzheimer's disease. Individuals with Alzheimer's disease begin with memory problems and progress to problems with concentration and short-term memory, personality changes, depression and depressive symptoms, inability to care for themselves, a deterioration of communication skills, failure to process information and no longer recognize objects and familiar people, and finally losing the ability to comprehend and produce speech, to control bodily functions, and to respond to stimuli.
Whereas individuals with Alzheimer's disease show slow and steady decrements in mental abilities, those with vascular dementia tend to show sudden, but often mild, losses with each stroke. As time passes, individuals tend to show improvement because the brain's plasticity leads other neurons to take on functions of those that were lost. Additional strokes usually follow, however, and with each stroke, brain matter is lost and it becomes harder for the remaining neurons to compensate for losses. As vascular dementia worsens, the symptoms are similar to those of Alzheimer's disease. However, vascular dementia is neurologically different from Alzheimer's disease. Postmortem analyses of the brains of people with vascular dementia show substantial deterioration of areas of the brain and disruptions in white matter but not the widespread abundance of plaques and tangles that accompany Alzheimer's disease.