Ballismus is a type of involuntary movement in which
one violently flings, swings, shakes, or jerks the arm(s)
and/or leg(s) in an uncoordinated manner. Ballismus is
caused by a lesion (damaged area such as a bleed or
tumor) in the part of the subthalamic nucleus and basal
ganglia opposite of the affected side of the body. The
subthalamic nucleus is an area in the lower part of the
brain that is believed to play a role in action selection.
The basal ganglia is a group of gray matter structures
(gray appearing tissues) located deep within the brain
that helps control movement. Infarcts to these areas
are the most common cause of ballismus, but ballismus
can also be caused by brain tumors. An infarct is an
area of tissue death that occurs due to a loss of
oxygen to that tissue region.
Usually, only one side of the body is affected, and thus the condition is then referred to
as hemiballismus (because "hemi" is Greek for "half"). This can be made worse by any
condition that affects the functioning of bodily systems such as a fever or abnormally high
blood sugar levels. Rarely will ballismus affect both sides of the body. Ballismus often
occurs with chorea. Chorea is involuntary, irregular, dance-like movements of the arms,
legs, and face. One example is Sydenham's chorea, which is a disease characterized by
fast, uncoordinated jerky movements of the feet, hands, and face. Ballismus comes from
the Greek word "ballismos" which means "jumping about."