DEVIATED NASAL SEPTUM
D
deviated nasal septum
See
nasal septum
.
deviation, sexual
An abnormal form of sexual behaviour,
most common in men, in w hich sexual
intercourse between adults is not the
final aim. Forms of sexual deviation
include
exhibitionism
,
fetishism
,
paedo-
philia
,
and
transvestism
.
Devic’s disease
A
rare
condition,
sometimes
called
neuromyelitis optica, in w hich there is
demyelination
of the fibres in the optic
nerves and the spinal cord. The condi-
tion begins with inflammation of the
optic nerves (see
optic neuritis
),
leading
to loss of vision. There are also attacks
of numbness, muscle weakness, and
loss of coordination in the parts of the
trunk and limbs below the diseased
area of the spine. In addition, the spinal
cord damage may lead to disruption of
urinary and bowel control and im pair-
ment of sexual function.
dexamethasone
A
corticosteroid drug
prescribed as a
nasal spray to relieve
nasal congestion
caused by allergic
rhinitis
(hay fever), as
eye drops in the treatment
of
iritis
(inflammation
of the
iris),
and
as
eardrops in the treatment of
otitis externa
(outer-ear infection).
Dexamethasone
is
given
in
tablet
form or by injection to treat severe
asthma
and other inflammatory disor-
ders, and to reduce inflammation of
the brain due to
head injury
,
stroke
,
or a
brain tumour
.
It may also be injected
into an inflamed joint to relieve the
symptoms of
osteoarthritis
.
Dexamethasone nasal spray may cause
nosebleeds; eye drops may cause irrita-
tion of the eyes. Prolonged use or high
doses of dexamethasone tablets may
cause the adverse effects common to
the corticosteroid group of drugs.
dexamfetamine
A central nervous system stimulant (see
amphetamine
drugs
;
stimulant
drugs
)
sometimes used to treat
narcolepsy
(a
sleep disorder). It is also used in chil-
dren with
attention deficit hyperactivity
disorder
who have not responded to
treatment with methylphenidate.
Because of its stimulant properties,
dexamfetamine has become a drug of
abuse. Excessive use leads to
anxiety
and
drug psychosis
.
W ith
prolonged
use,
physical tolerance develops: the drug’s
stimulant effects lessen and a higher
dose must then be taken to produce the
same effect.
Drug dependence
(a physical
or mental need for the
drug)
also
develops after repeated use.
DEXA scan
Dual-energy
X-ray
absorptiometry,
a
technique that measures bone density
by passing beams of low-dose radiation
through bone. DEXA scans are used to
assess the severity of the bone disorder
osteoporosis
.
(See also
densitometry
.)
dextran
A
polysaccharide
(a
type
of
carbo-
hydrate
) consisting of branched chains
of glucose
units.
Dextrans
that
are
formed by the action of bacteria on
sucrose in the mouth produce
plaque
(a
rough, sticky coating on the teeth),
w hich is a major cause of tooth decay
(see
caries, dental
).
Commercially manufactured prepar-
ations
of synthetic dextran solution
may be used in surgery or in emer-
gency treatment for
shock
,
to increase
the volume of the
plasma
(the fluid part
of the blood) in the circulation. Dex-
trans used for this purpose are known
as plasma expanders.
dextrocardia
A rare condition, w hich is present from
birth, in w hich the heart is situated in,
and points towards, the right-hand side
of the chest instead of the left. The
heart may also be malformed. Some-
times, the position of the abdominal
organs is also reversed, so that the liver
is on the left-hand side and the stom-
ach
is
on
the
right. The
cause
of
dextrocardia is not known.
No treatment is necessary unless the
heart is malformed, in w hich case sur-
gical correction may be performed.
A b n o r m a l p o s i t i o n
N o r m a l p o s i t i o n
Heart positions
In dextrocardia, the heart is situated in, and points
towards, the right-hand side ofthe chest instead
ofthe left-hand side.
dextromethorphan
A cough suppressant that is available
over the counter as an ingredient in
many
cough remedies
.
dextromoramide
An
opioid
analgesic drug
related
to
opium that is used to relieve severe pain
following injury or surgery and during
long-term
illnesses.
It
relieves
pain
quickly but has only a short duration of
action. Regular use of dextromoramide
can produce
drug dependence
.
dextropropoxyphene
A weak opioid
analgesic drug
that is
included in some compound analgesic
preparations. The drug works rapidly
and relieves m ild to moderate pain for
about four hours. Adverse effects of this
drug may include drowsiness, dizzi-
ness, nausea, and vomiting.
dextrose
Another name for
glucose.
diabetes, bronze
Another name for
haemochromatosis
,
a
rare genetic disease in w hich excessive
amounts of iron are deposited in tis-
sues. Bronze diabetes causes a bronze
skin
coloration,
and
sufferers
often
develop
diabetes mellitus
.
diabetes insipidus
A rare condition that is characterized
by excessive thirst and the passing of
large quantities of dilute urine. A per-
son with diabetes insipidus may pass
between five and
20
litres of urine
every 24 hours, provided that this out-
put is matched by a sufficient intake of
water. If the lost water is not replaced,
dehydration may occur, leading to con-
fusion, stupor, and coma.
Diabetes
insipidus
usually
results
from a failure of the
pituitary gland
to
secrete
ADH
(antidiuretic
hormone),
w hich normally regulates the amount
of water excreted in the urine. This fail-
ure may be due to a disease of the
pituitary gland, or may temporarily fol-
low brain surgery. A rare form of the
disease,
called
nephrogenic
diabetes
insipidus, is due to failure of the kid-
neys to respond to ADH.
Diagnosis mainly involves blood and
urine tests. A doctor may measure out-
put of urine over 24 hours. He or she
may also measure urine output when
fluid has been withheld for several
hours; an affected person w ill continue
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