CARPAL TUNNEL SYNDROME
carotenaemia
A harmless condition in w hich blood
levels of
carotene
,
an orange pigment in
certain vegetables, are very high as a
result of excessive intake of these foods.
Carotenaemia
may
cause
temporary
yellowing of the skin, especially on
the palms and soles. Unlike
jaundice
,
carotenaemia does not cause yellowing
of the whites of the eyes.
carotene
A yellow or orange pigment found in
carrots, tomatoes, and leafy green vege-
tables. The most important form
of
carotene is beta-carotene, an
antioxidant
.
Beta-carotene is converted in the intes-
tines into retinol (see
vitamin
A
), w hich
is essential for vision and healthy skin.
Excessive intake of foods containing
carotene may cause
carotenaemia
(tem-
porary yellowing of the skin).
carotid artery
Any of the main arteries of the neck
and
head. There
are
two
common
carotid arteries (left and right), each of
w hich divides into two main branches
(internal and external).
The left carotid artery arises from
the
aorta
and runs up the neck on the
left side of the
trachea
(w indpipe). The
right carotid artery arises from
the
subclavian artery (w hich branches off
the aorta) and follows a sim ilar route
on the right side of the neck. Just
above the level of the
larynx
(voice-
box), each carotid artery divides to
form an external carotid artery and an
internal carotid artery.
The external arteries have multiple
branches that supply most of the tissues
in the face, scalp, mouth, and jaws. The
internal arteries enter the skull to sup-
ply the brain and eyes. At the base of
the brain, branches of the two internal
carotids and the basilar artery join to
form a ring of blood vessels called the
circle of W illis. Narrowing of these ves-
sels may be associated w ith
transient
ischaemic attack (TIA)
;
obstruction
of
them causes a
stroke
.
The carotid arteries have two special-
ized sensory regions in the neck: the
carotid sinus, w hich monitors blood
pressure, and the carotid body, w hich
monitors the oxygen content of the
blood and helps to regulate breathing.
The carotid artery is one of the points
at w hich the
pulse
can be measured.
(See also
carotid bruit
;
carotid doppler
scanning
;
carotid sinus syndrome
. )
carotid bruit
An abnormal noise in a
carotid artery
(one of the major arteries supplying
the neck and head), w hich is due to
turbulent blood flow. A doctor can hear
the noise with a stethoscope placed on
the side of a person’s neck, over the
artery. A carotid bruit indicates narrow-
ing (stenosis) of the artery, usually due
to fatty deposits on the blood vessel
lining (see
atherosclerosis
) .
carotid doppler scanning
A method for assessing blood flow
through the
carotid arteries
(the major
arteries supplying the neck and head)
by
the
use
of
ultrasound scanning
.
Carotid doppler scanning is used to
investigate certain disorders, such as
carotid artery stenosis (narrowing of
the artery),
transient ischaemic attacks
,
and
stroke
,
that may be the result of
narrowing
of the
common
carotid
arteries and their branches.
An ultrasound transducer is moved
over each side of the neck in the area of
the
carotid
arteries.
The
transducer
emits
ultrasound
waves,
w hich
are
reflected off the moving blood cells
and blood-vessel walls to produce an
image on a screen. This image reveals
any narrowing of the arteries or turbu-
lence in blood flow.
carotid sinus syndrome
A condition mainly affecting elderly
people, in w hich the carotid sinus, a
structure w ithin the common
carotid
artery
of the neck that regulates blood
pressure, is overly sensitive.
The carotid sinus is a pocket in the
artery at the point where the vessel
divides to form two branches. It con-
tains sensors that continually monitor
blood pressure. W hen the blood pres-
sure is raised, the sinus sends messages
to the brain, w hich signals blood ves-
sels to widen and the heart rate to slow,
thus lowering the pressure.
In carotid sinus syndrome, the sinus
reacts too readily: simply turning the
neck suddenly or coughing can trigger
the sensors. As a result, the brain slows
the heart rate and lowers blood pres-
sure excessively, causing the affected
person to faint. This problem may be
avoided by the insertion of a
pacemaker
,
w hich w ill help to maintain a normal
heart rate, overriding any inappropriate
messages from the carotid sinus.
carpal tunnel syndrome
Numbness, tingling, and pain in the
thumb, index finger, and middle fin-
gers. Carpal tunnel syndrome is caused
by compression of the
median nerve
at
the wrist. The carpal tunnel, through
w hich the nerve passes, is a narrow gap
formed by the carpal bones of the wrist
and a ligament that lies over them. The
condition may affect one or both of the
hands and is sometimes accompanied
by weakness in the thumb. Symptoms
may be worse at night.
CAUSES
Carpal tunnel syndrome is common
among people who use computer key-
boards, w ho make constant, repetitive
hand movements. The condition also
occurs without obvious cause in m id-
dle-aged women. In addition, it is quite
common in pregnancy; in women who
have begun using
oral contraceptives
;
in
those w ho suffer from
premenstrual syn-
drome
;
and in men and women who
suffer from
rheumatoid arthritis
,
myxo-
edema
(thickening and coarsening of
the skin and other body tissues), and
acromegaly
(a condition in w hich there
is abnormal enlargement of the skull,
jaw, hands, feet, and internal organs).
TREATMENT
The condition often disappears without
any
treatment.
Persistent
symptoms
may be treated by the injection of a
corticosteroid drug
under the ligament.
C
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