to another occurs in hypomaniaand
mania. In depression, thinking becomes
slow, there is a lack of association, and
a tendency to dwell in great detail on
trivial subjects. In obsessive–compulsive
disorder, recurrent ideas seem to come
into a person’s mind involuntarily. Delu-
sions, which occur in schizophrenia and
other psychotic illnesses, may be an
expression of distorted thinking.
threadworm infestationA common
infestation with a small worm, ENTERO-
BIUS VERMICULARIS(pinworm), that lives
in the intestines. Threadworms primarily
affect children. The female adult thread-
worms are white and about 1 cm long
(large enough to see). They lay eggs in
the skin around the anus, and their
movements cause tickling or itching in
the anal region, often at night. Eggs are
transferred from the fingers to the mouth
to cause reinfestation or are carried on
toys or blankets to other children. Swal-
lowed eggs hatch in the intestine and
the worms reach maturity after a period
of 2–6 weeks. Diagnosis is made by see-
ing the worms or by applying a piece of
sticky tape to the anal area to collect
the worms or eggs. Treatment is with an
anthelmintic drug.
thrillA vibrating sensation felt when
the flat of the hand is held against an
area of the body. Thrill is caused by tur-
bulent blood flow in an arteryor the
heart. The term is also used to describe
the feeling produced by fluid within the
abdominal cavity in ascites.
throatA popular term for the pharynx.
The term is also sometimes used to
refer to the front of the neck.
throat cancerSee pharynx, cancer of;
larynx, cancer of.
thrombectomyThe removal of a throm-
busthat is blocking a blood vessel. It is
performed as an emergency procedure
if a major artery is blocked, or as a pre-
cautionary measure if there is a risk of
an embolusbreaking off. Before surgery,
the site of the thrombus is established
by angiographyand the patient may be
given anticoagulant drugs.
thromboangiitis obliteransAnother
name for Buerger’s disease.
thrombocyteAn alternative name for
a platelet.thrombocytopeniaA reduction in the
number of plateletsin the blood, result-
ing in a tendency to bleed. Sometimes
thrombocytopenic purpura(abnormal
bleeding into the skin) develops. The
cause may be a reduced rate of platelet
production or fast rate of platelet des-
truction. Thrombocytopenia can be a
feature of leukaemia, lymphoma, systemic
lupus erythematosus, megaloblastic
anaemia, or hypersplenism. It can also be
caused by exposure to radiation or,
more often, by an adverse reaction to a
prescribed drug such as a thiazide
diuretic. Idiopathic thrombocytopenic pur-
pura (ITP) is of unknown cause, but it
may be an autoimmune disorder.
Thrombocytopenia is confirmed by a
blood count. Any underlying disease is
treated if possible. Children with ITP
may not need treatment, but adults are
usually given corticosteroid drugs. If
thrombocytopenia persists, splenectomy
may be performed. When the cause is
known, treatment usually results in an
increase in platelet numbers.
thromboembolismThe blockage of a
blood vessel by a piece of a blood clot
(embolus) that has broken off from a
thrombuselsewhere in the circulation.
(See also thrombosis; embolism).
thrombolytic drugsSometimes called
fibrinolytic drugs, this group of drugs is
used to treat thrombosis, embolism, and
myocardial infarction. Thrombolytic drugs
act within blood vessels to dissolve clots.
Possible adverse effects include abnor-
mal bleeding and an allergic reaction.
thrombophiliaA tendency for blood to
clot too readily due to an inherited ab-
normality in proteins such as factor V. It
may not be recognized until specific cir-
cumstancessuch as injury or air travel
cause symptoms or signs. (See also
thrombosis, deep vein.)
thrombophlebitisInflammation of a
section of vein, usually just under the
skin, with clot formation in the affected
part. This can occur after minor injury to
the vein or as a complication of varicose
veinsor Buerger’s disease. The affected
blood vessel is swollen, red, and tender,
and feels hard. Fever and malaise may
occur. A blood clot may develop. Treat-
ment includes support with a bandage,THREADWORM INFESTATION THROMBOPHLEBITIST