pulse, slight fever, and profuse sweating.
Painful muscle spasms then develop, and
may result in asphyxiaif they affect the
larynxor chest wall. The spasms usually
subside after 10 to 14 days.
About half a million cases of tetanus
occur worldwide each year, but fewer
than 20 occur in the UK. The diagnosis
is made from the symptoms and signs,
and a course of tetanus antitoxininjec-
tions is started. Most people recover
completely if treated promptly.
Prevention of tetanus in the UK relies
on the DPT vaccinationbeing given rou-
tinely during childhood; booster shots
are given every 10 years.
tetanySpasms and twitching of the mus-
cles, most commonly in the hands and
feet, although the muscles of the face,
larynx, or spine may also be affected.
The spasms are caused by a biochemical
disturbance and are painless at first; if
the condition persists, the spasms tend
to become increasingly painful. Muscle
damage may result if the underlying
cause is not treated. The most common
underlying cause is hypocalcaemia. Other
causes include hypokalaemia, hypervent-
ilationduring a panic attack, or, more
rarely, hypoparathyroidism.
tetracosactideA drug used to test the
functioning of the adrenal glands. Tetra-
cosactide is a chemical analogue of the
natural hormone corticotrophin (ACTH).
ACTH stimulates the cortices of the
adrenal glands to secrete hormones such
as cortisol. To diagnose a disorder of the
adrenal glands, a tetracosactide injection
is given and the blood cortisol level
measured. Failure of the level to rise
indicates an abnormality.
tetracycline drugsA group of antibiotic
drugscommonly used to treat bronchitis,
acne, syphilis, gonorrhoea, nongonococcal
urethritis, and certain types of pneumonia.
If taken with milk, tetracyclines are not
absorbed effectively into the intestines.
Possible side effects include nausea,
vomiting, diarrhoea, worsening of kidney
disorders, rash, and itching. Tetracyclines
may discolour developing teeth and are
therefore not usually prescribed for chil-
dren under age 12 or pregnant women.
tetralogy of FallotA form of congenital
heart diseasein which the heart has 4
coexisting anomalies: displacement of
the aorta, narrowing of the pulmonary
valve, a hole in the ventricular septum,
and thickening of the right ventricle wall.
These cause poor oxygenation of the
blood pumped to the body, resulting in
cyanosisand breathlessness. Tetralogy of
Fallot occurs in about 1 in 1,000 infants.
Affected infants appear normal at birth.
Severely affected infants may become
cyanosed and breathless early in life.
Other symptoms include failure to gain
weight and poor development.
An ECG, echocardiogram (see echo-
cardiography), and sometimes cardiac
catheterizationare performed to confirm
the diagnosis and assess the severity of
the condition. The disorder is corrected
by open heart surgery.
tetraplegiaAn alternative term for the
condition quadriplegia.
thalamusOne of 2 structures within the
brainconsisting of a walnut-sized mass
of nerve tissue. The thalami sit at the
top of the brainstemand are connected
to all parts of the brain.
Each thalamus relays sensory infor-
mation flowing into the brain. Some
basic sensations, such as pain, may
reach consciousness within the thala-
mus. Other types of sensory information
are processedand relayed to parts of
the cerebral cortex (outer layer of the
brain), where sensations are perceived.
The thalamus seems to act as a filter
by selecting only information of particu-
lar importance. Certain centres in the
thalamus may also play a part in long-
term memory.
thalassaemiaA group of inherited blood
disorders in which there is a fault in the
production of haemoglobin. Many of the
red blood cells become fragile and
haemolyse (break up), leading to anaemia
(see anaemia, haemolytic). Thalassaemia
is prevalent in the Mediterranean, the
Middle East, and SoutheastAsia, and in
families originating from these areas.
Normal adult haemoglobin contains 2
pairs of globins (protein chains): alpha
and beta. In thalassaemia, a recessive de-
fective generesults in reduced synthesis
of 1 of the chains. Usually beta-chain pro-
duction is disturbed (beta-thalassaemia).
Beta-thalassaemia minor (thalassaemiaTETANY THALASSAEMIA
T