Parkinson's disease belongs to a group of conditions
called movement disorders. The four main symptoms are tremor, or
trembling in hands, arms, legs, jaw, or head; rigidity, or stiffness
of the limbs and trunk; bradykinesia, or slowness of movement; and
postural instability, or impaired balance. These symptoms usually begin
gradually and worsen with time. As they become more pronounced, patients
may have difficulty walking, talking, or completing other simple tasks. Not
everyone with one or more of these symptoms has Parkinson Disease, as the symptoms
sometimes appear in other diseases as well.
Parkinson Disease is both chronic, meaning it persists over a long
period of time, and progressive, meaning its symptoms grow worse over time.
It is not contagious. Although some Parkinson Disease cases appear to be hereditary, and a
few can be traced to specific genetic mutations, most cases are sporadic —
that is, the disease does not seem to run in families. Many researchers now
believe that Parkinson Disease results from a combination of genetic susceptibility and
exposure to one or more environmental factors that trigger the disease.
Parkinson Disease is the most common form of
parkinsonism, the name for a group of
disorders with similar features and symptoms. Parkinson Disease is also called primary
parkinsonism or idiopathic Parkinson Disease. The term
idiopathic means a disorder for which no cause has yet been found. While
most forms of parkinsonism are idiopathic,
there are some cases where the cause is known or suspected or where the
symptoms result from another disorder. For example, parkinsonism may result
from changes in the brain's blood vessels.