ABSTRACT
The subcortical degenerative diseases called the subcortical dementias, are caused by degeneration of the basal ganglia that is parts of the brain below the conscious cortex, which have a powerful influence over body movements and muscle tone. Dopamine depletion in the basal ganglia causes motor deficits, while dopamine problems in the frontal lobes generate cognitive and psychotic symptoms. Deep brain electrical stimulation (DBS) of the basal ganglia has proved to be disappointing in PD, but DBS of the pedunculopontine nucleus (PPN) has been very beneficial in helping to control two important and distressing symptoms of PD, i.e. freezing of gait and postural instability. Huntington's disease (HD) is a neurodegenerative disorder of the GABA neurons within the basal ganglia, notably the caudate nucleus first, followed by the putamen, with concurrent enlargement of the lateral ventricles. Mitochondrial DNA damage appears also to be implicated in the pathogenesis of not only Huntington's disease but also in Parkinson's disease and Alzheimer's disease.
