CHOROIDITIS
occurs w ithin or on the surface of large
bones, such as the femur (thigh bone),
causing pain and swelling.
The
condition
usually
appears
in
middle age. The tumour may develop
slowly from a noncancerous tumour
(see
chondroma
;
dyschondroplasia
)
or
may grow rapidly from an area of pre-
viously
normal
bone.
If a
lim b
is
affected,
amputation
of the
bone
above
the tumour usually results in a perman-
ent cure. Treatment of sites such as the
pelvis or ribs is more difficult.
chordae tendineae
Stringlike strands of fibre that attach the
flaps of the mitral and tricuspid
heart
valves
to the walls of the ventricles
(lower heart chambers). The chordae
tendineae, w hich are popularly known
as the heartstrings, prevent the valves
from turning inside out.
chordee
Abnormal curvature of the penis, usu-
ally downwards. Chordee most often
occurs in males with
hypospadias
,
a
birth defect in w hich the opening of
the urethra lies on the underside of the
penis instead of at the tip. It is usually
corrected by surgery, between the ages
of one and three years.
chorea
A condition that is characterized by
irregular, rapid, jerky movements, usu-
ally affecting the face, limbs, and trunk.
The movements are involuntary and,
unlike tics, they are not predictable but
occur at random.
Chorea disappears
during sleep. The disorder is sometimes
combined with athetosis
(continued
w rithing movements); this combined
condition is known as
choreoathetosis
.
TYPES AND CAUSES
Chorea arises from disease or distur-
bance of structures lying deep within
the brain (in particular, the paired nerve
cell groups called the
basal ganglia
) .
The
condition is a feature of
Huntington’s dis-
ease
and
Sydenham’s chorea
.
It may also
occur in pregnancy, when it is called
chorea gravidarum. In addition, chorea
may be a side effect of certain drugs,
including
oral
contraceptives
;
certain
drugs
for
psychiatric
disorders;
and
drugs for treating
Parkinson’s disease
.
TREATMENT
If the cause of chorea is an underlying
disease, the condition may be treated
with drugs that inhibit the nerve path-
ways
concerned with
movement.
If
chorea has occurred as a side effect of a
drug, the drug may be withdrawn and
a substitute provided.
choreoathetosis
A condition characterized by uncon-
trollable movements of the limbs, face,
and trunk. In this disorder, the jerky,
rapid movements typical of
chorea
are
combined w ith the slower, continuous
writhing movements of
athetosis
.
Choreoathetosis may occur in chil-
dren with
cerebral palsy
.
It may also be a
side effect of certain drugs.
choriocarcinoma
A rare, cancerous
tumour
that develops
from placental tissue (see
placenta
)
in
the
uterus.
Choriocarcinoma
usually
occurs as a complication of a
hydatidi-
form mole
(a noncancerous tumour that
arises in placental tissue); however, it
sometimes
develops
after
a
normal
pregnancy, a miscarriage, or an abor-
tion. Occasionally, the tumour may not
appear until months or even years after
the pregnancy that gave rise to it.
SYMPTOMS
There may be no early symptoms. The
tumour may become apparent because
of persistent bleeding from the vagina
after a miscarriage or abortion, or for
more than eight weeks following child-
birth. If it is left untreated, the tumour
destroys the walls of the uterus; and the
cancer may also spread in the blood-
stream to the vagina and vulva and then
to the liver, lungs, brain, and bones.
DIAGNOSIS AND TREATMENT
Any woman w ho has been treated for a
hydatidiform mole is screened regular-
ly by
ultrasound scanning
.
Blood and
urine levels of human chorionic gona-
dotrophin (HCG), a hormone that is
normally produced by the placenta, are
also measured because high levels of
this hormone in the body are associat-
ed with choreocarcinoma.
Treatment with
anticancer drugs
is
usually
very
successful.
Hysterectomy
(surgical removal of the uterus) may
also be necessary.
chorion
One of the two membranes that sur-
round the
embryo
.
The
chorion lies
outside the
amnion
,
has small finger-
like projections called the chorionic
villi, and develops into the
placenta
.
chorionic gonadotrophin
See
gonadotrophin, human chorionic
.
chorionic villi
The short, fingerlike projections that
extend from the surface of the
chorion
(the membrane that surrounds a fetus).
(See also
chorionic villus sampling
;
villus
. )
chorionic villus sampling (CVS)
A method of diagnosing genetic abnor-
malities in a
fetus
.
The test involves
taking a small sample of tissue from the
chorionic villi
at the edge of the
placenta
for laboratory analysis. The cells have
the same chromosome makeup as those
that form the fetus, so they can be used
to detect genetic abnormalities. After
removal, the villi cells are transported
to a laboratory for
chromosome analysis
.
CVS is offered to women at a higher-
than-normal risk of having a child with
a genetic disease, such as
thalassaemia
,
or a chromosomal abnormality, such as
Down’ssyndrome
.
It is normally performed
at around the 1 0th week of pregnancy
and can be carried out via the abdomen
(below) or vaginally, depending on the
location of the placenta. CVS slightly
increases the risk of
miscarriage
.
Sampling via the abdomen
A few chorionic villi are sucked from the placenta
through a hollow needle inserted into the abdomen.
choroid
A layer of tissue at the back of the
eye
,
beneath the
retina
. T h e
choroid contains
a network of blood vessels that supply
nutrients and oxygen to the retina and
to the surrounding tissues in the eye.
choroiditis
Inflammation of the
choroid
(the blood-
rich layer of tissue at the back of the
eye). Choroiditis may occur on its own
C
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