brain, spinal cord, and nerve disorders
Chorea, Athetosis, and Hemiballismus
Causes
Chorea and athetosis result from overactivity in the basal ganglia, the part of the brain that helps initiate and smooth out and coordinate intended (voluntary) movements initiated by nerve impulses from the brain. In most forms of chorea, an excess ofdopamine, the main neurotransmitter used in the basal ganglia, prevents the basal ganglia from functioning normally. Drugs and disorders that increasedopaminelevels or increase the sensitivity of nerve cells todopaminetend to worsen chorea and athetosis. The basal ganglia are collections of nerve cells located deep within the brain. They include the following: Caudate nucleus (a C-shaped structure that tapers to a thin tail) Putamen Globus pallidus (located next to the putamen) Subthalamic nucleus Substantia nigra The basal ganglia help initiate and smooth out muscle movements, suppress involuntary movements, and coordinate changes in posture. occur in Huntington Disease , a hereditary degenerative disorder. Choreamay also occur in the following: Sydenham chorea (also called St. Vitus’ dance or Sydenham disease), Nervous system (a childhood infection caused by certain streptococci) that is characterized by jerky, uncontrollable movements and that can last for several months Autoimmune Disorders , such as lupus ( Overactivity of the thyroid gland ( Hyperthyroidism ) A high blood sugar level (hyperglycemia) A low level ofparathyroid hormone(hypoparathyroidism) A tumor or stroke affecting a part of the basal ganglia called thecaudate nucleus Paraneoplastic Syndromes (symptoms caused by hormones produced by certain types of tumor or by antibodies produced by the immune system in response to the tumor) Pregnancy, causing a condition called chorea gravidarum that occurs during the first 3 months of pregnancy but disappears without treatment shortly after women give birth Rarely, use of oral contraceptives Use of certain drugs such as Levodopa/carbidopa in people with Parkinson disease, In a few people, antipsychotic drugs can cause a chorea called Side Effects of Antipsychotic Drugs (characterized, for example, by puckering of the lips and tongue or by choreoathetosis). Chorea sometimes develops in older people for no apparent reason. This chorea, called senile chorea, tends to affect the muscles in and around the mouth. However, if such movements develop, people should see a doctor. Hemiballismusis usually caused by a stroke that affects a small area just below the basal ganglia called thesubthalamic nucleus. Thesubthalamic nucleushelps control voluntary movements. 