EUSTACHIAN TUBE
E
no rational cause may be a sign of
mania
or of brain disease, or damage from
head injury
(particularly damage to the
frontal lobes),
dementia, brain tumours,
or
multiple sclerosis.
eustachian tube
The passage that runs from the middle
ear
into the back of the nose, just above
the soft
palate
(part of the roof of the
mouth). The eustachian tube is lined with
a smooth, moist, mucous membrane.
FUNCTION
The eustachian tube acts as a drainage
channel from the middle ear and main-
tains hearing by opening periodically to
regulate air pressure. The lower end of
the tube opens during swallowing and
yawning, allowing air to flow up to the
middle ear, equalizing the air pressure
on both sides of the
eardrum.
DISORDERS
When a viral infection, such as a cold,
causes blockage of the eustachian tube,
equalization cannot occur, resulting in
severe pain and temporary impairment
of hearing. A person with a blocked
eustachian tube who is subjected to
rapid pressure changes may suffer from
barotrauma
(pressure
damage
to
the
eardrum and other structures).
Glue ear
(the accumulation of secretions in the
middle ear) or chronic
otitis media
(m id-
dle-ear infection) may occur if the tube
is blocked, preventing adequate drain-
age from the middle ear.
These conditions, w hich often result
in partial hearing loss, are much more
common in
children. This
is
partly
because their
adenoids
are larger and
more likely to cause a blockage if they
become infected and partly because
children’s eustachian tubes are shorter
than those of adults.
euthanasia
The use of medical knowledge to end a
life painlessly in order to relieve suffer-
ing. Voluntary euthanasia refers to action
taken to end life at the patient’s own
request. In the UK, it is illegal to take
active measures to end a person’s life;
however, the withdrawal of treatment
that would prolong life may be consid-
ered under some circumstances.
euthyroid
A term used to describe a person whose
thyroid gland
is functioning normally.
The term “euthyroid” is used especially
to refer to someone who has been suc-
cessfully treated for either
hypothyroidism
(underactivity of the thyroid) or
hyper-
thyroidism
(overactivity of the thyroid).
Evan’s syndrome
An uncommon
autoimmune disorder
in
w hich the body wrongly makes two
antibodies
(immune system proteins):
one that attacks healthy red blood cells
(see
anaemia, haemolytic
)
and one that
destroys
platelets
(tiny
cells
in
the
blood that play a vital role in blood
clotting). The spleen is usually the main
site of cell destruction.
The anaemia can cause tiredness and
pallor, and the deficiency of platelets
may lead to bruising and a tendency to
bleed easily. The haemolysis (red cell
destruction) causes
jaundice
(yellowing
of the skin and the whites of the eyes).
A blood transfusion may be needed
in the early stages of the condition.
Cor-
ticosteroid drugs
may be prescribed to
control haemolysis and platelet destruc-
tion. In severe cases, the spleen may be
removed
(see
splenectomy
) .
The anti-
bodies may eventually disappear after
several months or years.
evening primrose oil
An oil extracted from the seeds
of
the plant O
enothera biennis
, commonly
called evening primrose. The oil con-
tains
an anti-inflammatory
substance
known as
gamolenic acid
and is believed
by some to be of benefit in treating
eczema
and
premenstrual syndrome
.
eversion
Turning outwards. The term is used
medically to describe a type of
ankle
injury or deformity in w hich the foot is
turned outwards.
evidence-based medicine
The use of medical or surgical treat-
ments
that have
been
evaluated for
effectiveness
and
safety
by
clinical
research. The research involves
random-
ized controlled trials
and often includes
meta-analysis
,
in w hich the results from
several trials are combined.
Evista
A brand name for
raloxifene
,
a drug
that is prescribed for the prevention
and treatment of
osteoporosis
in post-
menopausal women.
evoked potential
The electrical signal generated when a
sensory area, such as a
nerve
,
a
muscle
,
or the
retina
(the light-sensitive inner
layer at the back of the eye), is stimulated.
Tests to record evoked potentials are
used to diagnose problems affecting the
conduction
of signals along
sensory
nerves. (See also
evoked responses
. )
evoked responses
The tracing of electrical activity in the
brain in response to a specific external
stimulus. The evoked responses proce-
dure
is similar
to
that
for an
EEG
(electroencephalography).
The technique is used to check the
functioning of various sensory systems
(such as sight, hearing, or touch). The
information obtained can be used to
ANATOMY OF THE EUSTACHIAN TUBE
The eustachian tube connects the
middle ear with the back of the
nose. The tube is divided into two
separate parts: the uppermost part
runs through a bony canal and the
lower part is lined with cartilage.
M i d d le e a r
E u s t a c h i a n t u b e
N a s o p h a r y n x
( b a c k o f t h r o a t )
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