ASTHMA, CARDIAC
ATHEROMA
A
bronchodilators. An asthma attack that
has not responded to treatment with a
bronchodilator needs immediate assess-
ment and treatment in hospital.
asthma, cardiac
Breathing difficulty in
which
bronchospasm
and wheezing are
caused by accumulation of fluid in the
lungs
{pulmonary oedema).
This is usu-
ally due to reduced pumping efficiency
of the left side of the heart {see
heart
failure
) and is not true asthma. Treat-
ment is with
diuretic drugs.
astigmatism
A condition in which the
front surface of the
cornea
does not
conform to the normal “spherical” curve,
although the eye is perfectly healthy.
Because the cornea is unevenly curved,
it refracts {bends) the light rays that
strike it to differing degrees. The
lens
is
then unable to bring all the rays into
focus on the light-sensitive
retina.
A
minor degree of astigmatism is normal
and does not require correction. More
severe astigmatism causes blurring of
lines at a particular angle and requires
correction, which be achieved by spe-
cial “cylindrical” glasses that can be
framed at a precise angle, contact lens-
es that can give an even spherical
surface for focusing, or laser surgery.
astringent
A substance that causes tis-
sue to dry and shrink by reducing its
ability to absorb water. Astringents are
widely used in
antiperspirants
and to
promote healing of broken or inflamed
skin. They are also used in some eye or
ear preparations. Astringents may cause
burning or stinging when applied.
astrocytoma
A type of cancerous
brain
tumour.
Astrocytomas are the most com-
mon type of
glioma
, a tumour arising
from the glial {supporting) cells in the
nervous system. They most commonly
develop in the cerebrum {the main
mass of the brain). Astrocytomas are
classified in 4 grades (I-IV) according to
their rate of growth and malignancy.
The most severe type is called
glioblas-
toma multiforme.
Symptoms are similar
to those of other types of brain tumour.
Diagnostic tests include
CT scanning
or
MRI.
Treatment is with surgery and, in
some cases,
radiotherapy
in addition.
asylum
An outdated term for an institu-
tion providing care for the mentally ill.
asymptomatic
A medical term mean-
ing without
symptoms.
For example,
hypertension
is often asymptomatic and
is usually discovered during a routine
blood pressure test.
asystole
A term meaning absence of the
heartbeat (see
cardiac arrest).
ataxia
Incoordination and clumsiness
that affects balance and gait, limb or
eye movements, and/or speech. Ataxia
may be caused by damage to the
cere-
bellum
or to nerve pathways in the
brainstem
and spinal cord.
Possible
causes include injury to the brain or
spinal cord. In adults, ataxia may be
caused by
alcohol intoxication
, a
stroke
or a
brain tumour
affecting the cerebel-
lum or the brainstem, a disease of the
balance organ in the ear, or
multiple
sclerosis
or other types of nerve degener-
ation. In children, causes include acute
infection, brain tumours, and the inher-
ited condition
Friedreich's ataxia.
Symptoms of ataxia depend on the
site of damage, although a lurching,
unsteady gait is common to most
forms. In addition, damage to certain
parts of the brain may cause
nystagmus
and slurred speech.
CT scanning
or
MRI
may be used to determine the cause of
ataxia.
Treatment
of
the
condition
depends on the cause.
atelectasis
Collapse of part or all of a
lung
caused by obstruction of one or
more air passages in the lung. Obstruc-
tion may be caused by accumulation of
mucus, by an accidentally inhaled for-
eign body, by a tumour in the lung, or
by enlarged lymph nodes exerting pres-
sure on the airway.
The main symptom is shortness of
breath. There may also be a cough and
chest pain. The condition can be diag-
nosed by
chest X-ray
. Treatment is
aimed at removing the cause of the
blockage and may include
physiother-
apy
or
bronchoscopy
. If the obstruction
can be removed, the lung should rein-
flate normally.
atenolol
A
beta-blocker drug
commonly
used to treat
hypertension
,
angina
, and
certain types of
arrhythmia.
atheroma
Fatty deposits on the inner
lining of an artery that occur in
athero-
sclerosis
and restrict blood flow.
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