Alzheimer's Diseases
Alzheimer's disease (AD) is the most common type of dementia. It accounts for an estimated 60 to 80 percent of dementia cases. The most common symptom of the disease is short term memory lost. Therefore, AD is usually mistaken for normal aging.
Protein tau is believed to be the main constituent in brain degradation in AD. In a healthy brain, tau is phosphorylated and used to give microtubules structure and rigidity inside the neuron. However, in AD, the tau protein is hyperphosphorylated creating "phosphorylated tau (p-tau)". This p-tau breaks off from the microtubules and clumps together causing neurofibrillary tangles (NFT). This, in turn, causes the microtubules to loose their rigidity and start to break apart. The result is breakdown of the brains neuron transport system. The other main factor in brain degradation in AD is associated with a sticky protein called β-amyloid. The beta amyloid is a fragment from the amyloid precursor protein (APP) which is a regulator of synapse formation. In a normal brain, an enzyme called alpha secretase, snips APP, releasing a large fragment of the protein from the cell membrane. Another enzyme, Gamma secretase, snips APP in another place, releasing a different fragment from the cell membrane. In AD, the first cut is made by a different enzyme, Beta secretase (which becomes more active in the diseased brain), and the second cut is made by Gamma secretase, which releases small fragments of APP called Beta-amyloid peptide. These Beta-amyloid fragments clump together and create oligomers. As more and more oligomers clump together, they create insoluble fibrils that impede neuron function by sticking to axons and synapses. These two dysfunctions lead to the symptoms associated with Alzheimers that include: gradual memory loss, problems planning or problem solving, finishing daily activities, confusion with time, or problems with speaking or words. |
Formation of Tau tangles and amyloid plaques:
http://www.lookfordiagnosis.com/mesh_info.php?term=Amyloid+Precursor+Protein+Secretases&lang=1
http://alzheimer-unb.blogspot.com/ Click the video link for more info:
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Huntington's Disease
Huntington's Disease is an inherited neurodegenerative disorder that causes nerves in the brain to break down. Although hereditary, only 5-10 people out of 100,000 have this disease. It is extremely rare in Japan and Finland, but very common in the Lake Maracaibo region in Venezuela with every 400 out of 100,000 with the disease. The primary symptoms of Huntington's disease are dementia, gradual increase in abnormal involuntary movement, and psychiatric disturbances.
This genetic defect occurs on chromosome 4 where the CAG repeat occurs more than it does in a normal human being. As the gene is passed down, the number of repeats increase, causing the onset of Huntington's disease to occur at an earlier age. Patients die from the disease within 15-20 years after being diagnosed. There is currently no cure for this disease, but the goal to slow the progression of Huntington's |
An MRI of a patient's brain with a severe case of Huntington's disease. The brain on the right is normal. The brain on the left is diseased:
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Vascular Dementia
Vascular dementia is caused by strokes that occur from blockage of blood flow to the brain. Cognitive functions start to decrease after blockage of blood flow and increasingly become worse as time passes.
Vascular dementia is considered to be the 2nd most common type/cause of dementia following Alzheimer's disease. The symptoms are very similar to Alzheimer's and include disorientation, confusion, vision loss, and difficulty speaking and understanding speech. Like other dementias, the life span of a patient with vascular dementia is shortened. An individual who develops dementia after a stroke usually only lives another three years. |
Distribution of dementia pie chart:
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Frontotemporal Dementia
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Degradation of the frontal temporal lobe. The bottom is the normal brain. The top is the diseased brain associated with volume loss:
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Parkinson's Dementia
Parkinson's Disease affects 1.5% of people 65 years of age or older. PD is defined physiologically as cell loss in the pigmented dopaminergic cells which are located in the substantia nigra, pars compacta, associated with Lewy bodies in some surviving neurons.
The symptoms of Parkinson's Disease include excessive movement (tremor) of the skeletal muscles,memory impairment, attention disturbances, visuospatial dysfunctions. The point-prevalence of dementia in PD is around 30%.
Most common treatments are medications to improve symptoms. In severe cases, surgery is used to regulate parts of the brain to relieve symptoms.
The symptoms of Parkinson's Disease include excessive movement (tremor) of the skeletal muscles,memory impairment, attention disturbances, visuospatial dysfunctions. The point-prevalence of dementia in PD is around 30%.
Most common treatments are medications to improve symptoms. In severe cases, surgery is used to regulate parts of the brain to relieve symptoms.