This inherited condition is fatal and usually ends with the patient choking or dying of pneumonia. This condition is also known as Huntington's Chorea
The most noticeable symptom of Huntngton's disease is continuous involuntary, out of control, movement across the whole body. Eventually, the abilities to speak, stand, and walk are impaired. Dementia occurs as learning difficulties and thinking problems. There may also be changes in personality, such as depression.
Neuropathological observations have shown that sufferers have general brain shrinkage of up to 20%, with a loss of neurons over a wide range of structures, but most significantly in the striatum where 95% of neurons can be lost in advanced cases. MRI imaging techniques have detected large increases in the size of the ventricles of the brain as tissue recedes, while PET scans show that there is a reduction in glucose metabolism in the striatum, which may be the reason these cells die. Levels of dopamine and glutamate seem fairly normal, just a slight elevation and reduction respectively in advanced cases. However, this constant level of dopamine may contribute to the problem. Some of the cells which degenerate are GABA cells which act to inhibit dopamine. The lost of this inhibitory device could be a significant factor in the progression of Huntington’s disease. This view is further supported by the observations that dopamine antagonists tend to alleviate symptoms, whereas L-DOPA has been found to exacerbate them.
There are very few effective treatments for Huntington’s disease, and no means at all to halt its progression. However, the most logical course of action seemed to be finding a way to alleviate the GABA degeneration, in a similar way to the dopamine replacement in Parkinson's disease sufferers. But such a method has failed to work because the GABA system acts too quickly and the simple artificial replenishment of GABA does not mimic normal function. This additional GABA also affects surrounding areas of the striatum which are not degenerating. The only currently available treatment that has shown any success is the use of dopamine antagonists, but the efficacy of this treatment is reduced with the disease's inexorable progression.
Effective treatment seems to be impossible without identifying and understanding the defective gene which causes Huntington’s disease. Such knowledge could allow affected foetuses to be identified, but there are obvious ethical issues here. There has however, been speculation that the tissue degeneration could be caused by the production of a toxin within the striatum, or its connected structures. One possible chemical could be quinolinic acid, which is produced in human brains. External toxins have also been suggested. Kanic acid, which kills cells, has been found to replicate the chemical changes seen in Huntington's when injected into rat striatum, but nothing more. There is also the possibility of excess glutamaic acid causing the cataclysmic over-stimulation of cells. If this is so, the blocking of striatal NMDA receptors may prove a successful treatment.
As with many degenerative brain conditions, there is no current cure, and certianly no greatly effective treatment can be provided until the aetiology of the condition has been fully understood.
"Brain, Biochemestry and Brain Disorders", P. G. Strange, Oxford University Press, 1992