The symptoms and characteristics of juvenile Huntington’s Disease.
What parts of the brain are affected in juvenile HD?
At autopsy, individuals who have died from juvenile HD show an even more widespread pattern of brain degeneration than that seen in adult-onset HD. As in the adult form, there is severe degeneration of the caudate and putamen. (See Figure D-4.) The caudate and the putamen are responsible for regulating voluntary movement, and it is thought that damage to these parts of the brain is responsible for many of the movement problems — especially the chorea — that individuals with HD experience. (See Figure E-1.)
A characteristic that is seen more often in the juvenile form than in the adult form is extreme gliosis of the globus pallidus (Figure E-1). Gliosis is excess growth of what are called spider cells (see Figure E-2) — cells that normally provide supporting and protective tissue for nerve cells. Some individuals with adult-onset HD experience rigidity (instead of chorea), and case studies of several of these individuals have also shown damage to the globus pallidus. Hence, it is thought that abnormality of the globus pallidus may be responsible for the rigidity seen in juvenile HD.
Analysis of juvenile HD brains shows damage to many areas,
but the pattern of damage is not consistent between individuals. Loss of neurons
in the
Purkinje cells and
granule cells of the
cerebellum is often seen in the juvenile but not the adult form. Other areas
of damage sometimes include the
dentate nucleus, hippocampus,
and neocortex.
The dentate nucleus is responsible for rapid movements, and the hippocampus
deals with the transfer of information from short-term to long-term memory.
The neocortex constitutes about 85% of the brain’s total mass, and it is believed
to be responsible for higher cognitive functions, such as language and memories.
It is currently not known how damage to these areas of the brain manifests itself
as symptoms in people with juvenile HD.
Last Modified: 9-16-02
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At autopsy, individuals who have died from juvenile HD show an even more widespread pattern of brain degeneration than that seen in adult-onset HD. As in the adult form, there is severe degeneration of the 
