<unk>  is a degenerative disorder of the central nervous system that often impairs the sufferer's motor skills and speech.<unk>  belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia) and, in extreme cases, a loss of physical movement (akinesia). The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia, normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level cognitive dysfunction and subtle language problems.<unk>  is both chronic and progressive.<unk>  is the most common cause of parkinsonism, a group of similar symptoms.<unk>  is also called "primary parkinsonism" or "idiopathic<unk> " (having no known cause). While most forms of parkinsonism are idiopathic, there are some cases where the symptoms may result from toxicity, drugs, genetic mutation, head trauma, or other medical disorders.
Parkinson's disease
Parkinsonism
Pick's disease
Alzheimer's disease
Dementia with Lewy bodies
Progressive supranuclear palsy
Canavan disease
Early-onset Alzheimer's disease