I
DELTOID
déjà vu
French for “already seen” . A sense of
having already experienced an event
that is happening at the moment. Fre-
quent occurrence may sometimes be a
symptom of
temporal lobe epilepsy
.
Dejerine-Roussy syndrome
A rare neurological disorder, also called
thalamic syndrome or central pain syn-
drome, that results from damage to the
thalamus
,
the part of the brain that pro-
cesses sensory information.
The main symptom is severe pain,
possibly accompanied by other abnor-
malities such as loss of sensation or a
“ crawling” feeling in the skin.
delayed allergy
A type of
hypersensitivity
reaction that,
unlike most forms of
allergy
,
does not
develop immediately on exposure to a
particular
allergen
(a normally harmless
substance that causes a reaction in peo-
ple who have become sensitized to it).
Delayed allergies, also called type IV
hypersensitivity reactions, may result
from bacterial, viral, fungal, or proto-
zoal infections or from
vaccination
with
a live virus vaccine. Examples of such
delayed allergic reactions include
con-
tact dermatitis
and the body’s response
to infection in
tuberculosis
.
delayed dentition
The
late
eruption of teeth
.
The
term
“ delayed dentition” may refer to the
eruption of the first deciduous teeth
(see
primary teeth
) after the end of the
13 th month of life or to the eruption
of the first
permanent teeth
after the sev-
enth year of life. Delayed dentition is a
feature of various conditions that result
in generally restricted growth (see
short
stature
) ,
such as
hypothyroidism
.
delayed puberty
Onset of
puberty
(sexual maturation)
after the age of 14. In most cases, the
child is simply developing at a slower
rate than normal, a tendency that often
runs in families, but in some cases
there may be an underlying disorder.
One possible underlying cause of
delayed puberty is underproduction of
sex hormones. Rarely,
the condition
results from a problem with the
hypo-
thalamus
or the
pituitary gland
,
w hich
are responsible for secreting sex hor-
mones; a genetic abnormality affecting
sexual development, such as
Klinefelter’s
syndrome
in boys or
Turner’s syndrome
in
girls; or a long-term illness, such as
Crohn’s disease
.
Certain lifestyle factors,
such as excessive exercise or an inade-
quate diet, may also delay puberty.
Treatment depends on the underly-
ing cause. If delayed puberty runs in
the child’s family, no action may be
needed. In some cases, however, condi-
tions causing delayed puberty may also
lead to
infertility
,
so the child may need
further investigations in the future if he
or she wishes to have children.
delayed shock
A common term for severe mental or
physical reactions that may occur some
time after a traumatic event (see
post-
traumatic stress disorder; shock
;
stress
. )
Delhi belly
A popular name for
gastroenteritis
and
infective diarrhoea caused by ingesting
contaminated food or water.
delinquency
Criminal behaviour in a young person
who
is
below
the
official
age
at
w hich he or she can be prosecuted.
The term is often extended to include
behaviour such as
drug abuse,
playing
truant, or running away from home.
Delinquency that occurs in juveniles is
probably a result of a combination of
social, psychological, and biological fac-
tors.
Child guidance
or
family therapy
may
be recommended. Persistent offenders
may be sent to special schools, taken
into care, or made wards of court.
delirium
A state of acute mental confusion, com-
m only brought on by physical illness.
Symptoms vary according to personal-
ity, environment, and the severity of
illness. They may include
failure
to
understand events or remember what
has been happening, physical restless-
ness, mood swings, hallucinations, and
panic. Fever and disturbances of body
chemistry are often contributory factors.
Children and older people are most
susceptible to delirium , particularly as
a result of infection, following surgery,
or when there is a pre-existing brain
disturbance
(such as
dementia
in an
elderly person). Drugs, poisons, and
alcohol are common precipitants.
delirium tremens
A state of confusion accompanied by
trembling and vivid hallucinations. It
usually arises in chronic alcoholics after
withdrawal or abstinence from alcohol.
Early symptoms
include restlessness,
agitation, trembling, and sleeplessness.
The person may then develop a rapid
heartbeat, fever, and dilation of the
pupils. Sweating, confusion, hallucina-
tions, and convulsions may also occur.
Treatment consists of rest, rehydra-
tion, and sedation. Vitamin injections,
particularly of thiamine (see
vitamin B
complex
) ,
may be given, as some symp-
toms are linked to thiamine deficiency.
delivery
The expulsion or extraction of a baby
from
the
mother’s
uterus.
In
most
cases, the baby lies lengthwise in the
uterus with its head facing downwards;
it is delivered head first through the
vaginal opening by a combination of
uterine contractions and the mother’s
pushing (see
childbirth
) .
If the baby is
lying
in an abnormal position
(see
breech delivery
;
malpresentation
) ,
if uter-
ine contractions are weak, or if the
baby’s head is large in relation to the
size of the mother’s pelvis, a
forceps
delivery
or
vacuum extraction
may
be
required. If a vaginal delivery is im pos-
sible or dangerous to the mother or the
baby, a
caesarean section
is necessary.
deltoid
The triangular muscle of the shoulder
region that forms the rounded flesh of
the outer part of the upper arm, and
D
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