I
TREATMENT
The most important aspect of treatment
for Alzheimer’s disease is the provision
of suitable nursing and social care for
sufferers and support for their relatives.
Tranquillizer drugs
can
often improve
difficult behaviour and to help with
sleep. Treatment with
acetylcholinesterase
inhibitors,
such as rivastigmine and don-
epezil, may slow the progress of the
disease for a time, but will not improve
mental ability. Side effects such as nau-
sea and dizziness may occur.
amalgam, dental
A material, consisting of an alloy of mer-
cury with other metals, that is used as
fillings
for
teeth.
Amalgam
is
soft
enough to be easily workable by the
dentist but sets rapidly into a hard,
strong solid (see
filling, dental).
amantadine
An
antiviral drug
that is used in the pre-
vention and treatment of
influenza
A.
Amantadine is also used to help relieve
symptoms of
Parkinson’s disease.
amaurosis fugax
Brief loss of vision, lasting for seconds
or minutes, usually affecting one eye
only and
caused by the temporary
blockage of a small blood vessel in the
eye by an
embolus
(a particle of solid
matter such as cholesterol or clotted
blood). These emboli are carried in the
bloodstream from diseased arteries in
the neck or, rarely, the heart. Sufferers
typically experience a loss or dimming
of vision, in one eye only, rather like a
shade being pulled down or up.
Attacks may be infrequent, or they
may occur many times a day, which
indicates an increased risk of
stroke
and
requires medical investigation.
ambidexterity
The ability to perform manual skills,
such as writing or using cutlery, equally
well with either hand because there is
no definite
handedness
(preference for
the use of one hand in particular).
Ambidexterity is an uncommon and
often familial trait.
amblyopia
A permanent defect of visual acuity in
which there is usually no structural
abnormality in the eye. In many cases,
there is a disturbance of the visual
pathway between the
retina
and the
brain. The term amblyopia is also some-
AMENORRHOEA
times applied to toxic or nutritional
causes of decreased visual acuity, as in
tobacco-alcohol amblyopia.
If normal vision is to develop during
infancy and childhood, it is essential
that clear, corresponding visual images
are formed on both retinas so that com-
patible nerve impulses pass from the
eyes to the brain. If no images are
received, normal vision cannot develop.
If the images from each eye differ
markedly, one will be suppressed to
avoid double vision.
CAUSES
The most common cause of amblyopia
is
squint
(a deviation of one eye relative
to the other) in young children. Failure
to form normal retinal images may also
result from congenital (present from
birth)
cataract
(opacity of the lens of the
eye), and severe, or unequal, focusing
errors, such as when one eye is normal
and there is an uncorrected large degree
of
astigmatism
in the other. Toxic and
nutritional amblyopia may be the result
of damage to the retina and/or the
optic nerve.
TREATMENT AND OUTLOOK
The usual treatment for amblyopia due
to squint is patching (covering up the
good eye to force the deviating eye to
function properly). Surgery to place the
deviating eye in the correct position
may be necessary. Glasses may be need-
ed to correct severe focusing errors.
Cataracts may be removed surgically.
After the age of eight, amblyopia cannot
usually be remedied.
ambulance
A vehicle for transporting sick, injured,
or disabled people, usually to hospital,
that is staffed by trained personnel who
can provide emergency treatment dur-
ing the journey.
ambulatory ECG
In ambulatory
ECG
(electrocardiography),
a wearable device called a
Holter monitor
is used to record the electrical activity
of the heart by means of electrodes
attached to the chest. The monitor is
usually worn for at least 24 hours and
detects intermittent
arrhythmias
(abnor-
mal heart rates and rhythms). It is also
used to assess the programming of a
cardiac pacemaker. The wearer presses a
button on the monitor to mark the
recording whenever symptoms occur.
The recording can be analysed later to
determine
whether
the
periods
of
arrhythmia coincide with the symp-
toms. In some cases, the patient can
send the recording over the telephone
by means of
telecardiography
(transmis-
sion of an impulse to a site that is
remote from the patient).
amelioration
In medical usage, improvement in the
medical condition of a patient.
amelogenesis imperfecta
An inherited condition of the teeth in
which the enamel is either abnormally
thin or is deficient in calcium. The teeth
of affected individuals may be pitted and
discoloured (see
discoloured teeth
) and
more susceptible to dental
caries
(tooth
decay) and wear.
amenorrhoea
The absence of menstrual periods. Pri-
mary amenorrhoea is defined as failure
to start menstruating by the age of 16.
Secondary amenorrhoea is the tempo-
rary or permanent cessation of periods
in a woman who has menstruated regu-
larly in the past.
PRIMARY AMENORRHOEA
The main cause of primary amenor-
rhoea is the delayed onset of
puberty
.
The delay may not indicate a disorder
but, rarely, may result from a disorder of
the
endocrine system,
such as a
pituitary
tumour, hypothyroidism
(underactivity of
the thyroid gland), an
adrenal tumour,
or
adrenal hyperplasia.
Another rare cause
of delayed puberty is
Turner’s syndrome,
in which one female sex chromosome
is missing. In some cases, menstruation
fails to take place because the vagina or
uterus has been absent from birth. It
may also fail to occur because there is
no perforation in the hymen (the mem-
brane across the opening of the vagina)
to allow blood to escape.
SECONDARY AMENORRHOEA
The most common cause of temporary
secondary amenorrhoea is
pregnancy
.
Secondary amenorrhoea may also be
caused by hormonal changes that occur
as a result of stress,
depression, anorexia
nervosa,
certain drugs, or a pituitary or
thyroid disorder. Another possible cause
is a disorder of the ovary, such as poly-
cystic ovary (see
ovary, polycystic)
or an
ovarian tumour. Amenorrhoea occurs
permanently after the
menopause
or
following
a
hysterectomy
(a
surgical
operation to remove the uterus).
INVESTIGATION AND TREATMENT
Investigation of amenorrhoea usually
involves a physical examination and
A
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