Q: Let’s back up a bit. I think I need to know a little more about dementia before we go any further. For starters, what is it?A: Dementia is a loss of intellectual function. It includes impairment of more than one cognitive, or intellectual, ability, is persistent, is severe enough to interfere with a person’s daily functioning and is often progressive, meaning it gets worse with time.
Q: Which terms are most commonly used today?A: Generally, experts refer to dementia by the name of the disease or disorder that is causing it. But generic terms, such as dementia, senile dementia and presenile dementia, are used when the underlying cause is not known or when the speaker is referring to dementia in general.
Pick's disease and the frontal dementias
The story starts, as it should, before Pick. Louis Pierre Gratiolet (1854) was responsible for renaming the cerebral lobes after their overlying skull: thus 'anterior' became 'frontal' lobe. He made no assumption as to the function of the 'anterior extremity of the cerebral hemisphere'. 'Phrenologists', however, did and related reflective and perceptive functions (qualitatively defined) to the forehead (Anonymous, 1832) (for the science of phrenology see Combe, 1873; Lanteri-Laura, 1970). 'Modular' assumptions (i.e. a one-to-one correlation between mental function and brain site) involving the frontal lobes started only during the 1860s, following reports on dysfunction of language in lesions of the frontal lobes (Broca, 1861; Henderson, 1986). These claims ran parallel to those of Jackson's that the cerebral cortex was the general seat of personality and mind (Jackson, 1894). Meynert (1885) believed that 'the frontal lobes reach a high state of development in man' but still defined mental disorders as diseases of the 'fore-brain' (by which he meant 'prosencephalon' or human brain as a whole).... read more »
Huntington's Disease (Huntington's Chorea)
Huntington's Disease (HD) is a brain disorder that affects a person's ability to think, talk, and move.
The disease destroys cells in the basal ganglia, the part of the brain that controls movement, emotion, and cognitive ability. HD is caused by a mutation in a gene on chromosome 4. The job of its protein product, huntingtin, is to direct the delivery of small packages (vesicles containing important molecules) to the outside of the cell. Normally, the coding region of this gene contains the DNA sequence "CAG" repeated again and again. The number of times this triplet is repeated varies from person to person, ranging from 10 to 26 times. People with HD have an abnormally high number of these CAG triplets, approximately 40 or more. This likely disrupts the function of the gene's protein product, but how the expansion of the CAG repeat causes disease is unknown. Somehow the brain cells of HD patients accumulate clumps of protein that become toxic, resulting in cell death. Some patients lose more than 25% of their brain cells before they die.
How do people get Huntington's Disease?Huntington's disease is inherited in an autosomal dominant pattern. This means that everyone who inherits the faulty gene will eventually get the disease. A parent with a mutation in the HD gene has a 50 percent chance of passing on the disease to their children.
Huntington's disease symptoms include:
- Involuntary movements
- Psychiatric symptoms such as depression, anxiety and psychosis
- Gait abnormalities with falling
- Cognitive decline (dementia)
Patients with Huntington's disease possess a different gene than those without it. Neurologists at Emory are now able to predict if an at-risk patient will develop Huntington's disease. Huntington's disease is a genetic disorder caused by a mutation in the gene huntingtin. The gene is inherited in an autosomal dominant fashion, which means that children of a person with Huntington's disease have a 50% chance of inheriting it. Every patient who inherits the gene ultimately develops the disease. ... read more »