Encyclopedia of Health and Medicine

242 The Nervous System
though often are abrupt and exaggerated. In its
mildest form chorea appears as restless fidgeting;
in its most severe form (called ballism) chorea prevents
mobility and actions such as holding objects.
Chorea occurs in numerous neurologic conditions,
including HUNTINGTON’S DISEASE (formerly called
Huntington’s chorea), PARKINSON’S DISEASE, SYS-
TEMIC LUPUS ERYTHEMATOSUS (SLE), untreated NEONA-
TAL JAUNDICE (kernicterus), RETINITIS PIGMENTOSA,
and CEREBRAL PALSY. Some research suggests
autoimmune processes contribute to some forms
of chorea. One form of chorea, Sydenham’s
chorea, results from streptococcal INFECTION that
migrates to the brain after untreated or undertreated
STREP THROAT.
The diagnostic path depends on whether there
are known neurologic conditions or the chorea is
a new symptom occurring without a known
underlying neurologic cause. In the latter situation
the doctor conducts generalized BLOOD tests to
measure thyroid HORMONE levels, electrolyte levels,
cell composition of the blood, and antibodies for
streptococcus. The clinician may also conduct
diagnostic imaging procedures such as MAGNETIC
RESONANCE IMAGING (MRI) and COMPUTED TOMOGRA-
PHY (CT) SCAN to assess the brain’s structure. Such
procedures will show tumors, STROKE, and
anatomic abnormalities that could be responsible
for the chorea.
Treatment may include ANTIBIOTIC MEDICATIONS
when blood tests identify, or the doctor suspects,
strep infection. Antiseizure medications, MUSCLE
RELAXANT MEDICATIONS, and some of the ANTIPSY-
CHOTIC MEDICATIONS (notably haloperidol) often
relieve the chorea. Forms of chorea that result
from transient conditions typically improve or go
away within weeks to months. Forms of chorea
that result from permanent damage, such as TRAU-
MATIC BRAIN INJURY (TBI) or HYPOXIA (extended oxygen
deprivation), or from degenerative conditions,
such as Huntington’s disease, do not improve and
may worsen as the underlying neurologic condition
progresses.
See also ANTIBODY; AUTOIMMUNE DISORDERS; DYSTO-
NIA; RHEUMATIC HEART DISEASE; SPINAL CORD INJURY;
THYROID GLAND; TIC.
cognitive function and dysfunction The abilities
to think, reason, concentrate, process language,
and remember are key functions of the BRAIN.
Numerous metabolic and neurologic conditions
affect these functions, some transiently and others
permanently. Medications may also alter cognitive
function, either intentionally (as with the acetylcholinesterase
inhibitors to treat ALZHEIMER’S DIS-
EASE) or as undesired side effects. Adequate
cognitive function is essential for learning as well
as for independent living.
The two frontal lobes of the cerebrum conduct
most of the functions of cognition, with the other
cerebral lobes contributing processes such as sensory
input and behavioral cues. The prefrontal
areas of the frontal lobes are the most active in
regard to cognitive functions, performing functions
related to analytic thought, judgment, and
concentration. Other areas of the frontal lobes
regulate motor movement necessary for language
expression and speech. The temporal lobes,
located beneath and somewhat behind the frontal
lobes, interpret language input and recall memories.
One temporal lobe also contains the speech
center. The structures of the limbic system,
notably the amygdala and the hippocampus, control
the storage of recent memories.
Symptoms and Diagnostic Path
The symptoms of cognitive dysfunction vary
according to the damaged area of the brain. Symptoms
tend to appear gradually when the cause of
the damage is a progressive neurologic disorder. A
person in the early stages of cognitive loss may:
• become easily confused
• get lost on familiar routes
• be unable to perform tasks such as using a
checkbook or reading a book
• say the wrong words
• fail to remember recent events
When the cause of cognitive dysfunction is
damage to the brain that occurs as a result of
TRAUMATIC BRAIN INJURY (TBI) or STROKE, the cognitive
loss is generally obvious though may improve
over time and with treatment. The diagnostic path
begins with a comprehensive medical examination,
including assessment of PERSONAL HEALTH HIS-
TORY, and a general NEUROLOGIC EXAMINATION. The