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III. Diseases primarily affecting the basal ganglia

A.  Huntington Disease - expanded polyglutamine repeat

     1. Age of Onset:  usually occurs between the ages of 30 and 50; death in 5‑25 years.

     2. Location of Lesions: caudate, putamen, globus pallidus and cerebral cortex.

     3. Clinical Presentation: may begin with some combination of mood and personality                changes, cognitive decline, clumsiness, extrapyramidal motor abnormalities, especially                chorea (bursts of movement). Thus two types of symptoms occur:

                a. Behavioral and cognitive changes, leading to dementia
                b. Increasingly severe movement disorder

     4. Pathogenesis:  loss of projection neurons in basal ganglia with resulting                                  deficiency of GABA, enkephalin, and substance P. One theory proposes that an          excitotoxic mechanism may be involved in the pathogenesis of cell death.

Illustration of basal ganglia anatomy. The striatum consists of the caudate and putamen. The lenticular nucleus consists of putamen and globus pallidus. Connections with the subthalamic nucleus and substantia nigra are important in control of movement.
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