Parkinson's disease (
PD), also known as
idiopathic or
primary parkinsonism,
hypokinetic rigid syndrome, or
paralysis agitans, is a
degenerative disorder of the
central nervous system mainly affecting the
motor system. The motor symptoms of Parkinson's disease result from the death of
dopamine-generating cells in the
substantia nigra, a region of the
midbrain. The causes of this
cell death are poorly understood. Early in the course of the disease, the most obvious symptoms are
movement-related; these include
shaking,
rigidity,
slowness of movement and
difficulty with walking and
gait. Later,
thinking and behavioral problems may arise, with
dementia commonly occurring in the advanced stages of the disease, and
depression being the most common
psychiatric symptom. Other symptoms include sensory,
sleep, and
emotional problems. Parkinson's disease is more common in older people, with most cases occurring after the age of 50; when it is seen in young adults, it is called young onset PD.