trifluoperazineAn antipsychotic drug
used to treat schizophrenia.
trigeminal nerveThe 5th cranial nerve.
A trigeminal nerve arises from the brain-
stem. Both nerves divide into 3 branches
that supply sensation to the face, scalp,
nose, teeth, lining of the mouth, upper
eyelid, sinuses, and the front portion of
the tongue. They stimulate salivaand
tearproduction and contraction of jaw
muscles for chewing.
trigeminal neuralgiaA disorder of the
trigeminal nervein which brief episodes
of severe, stabbing pain affect the
cheek, lips, gums, or chin on 1 side of
the face. The disorder usually occurs
over age 50. Pain may come in bouts
that last for weeks at a time. The cause
is uncertain, and pain is often brought
on by touching the face, eating, drink-
ing, or talking. Analgesic drugsmay be
tried, but often, carbamazepineis more
effective. If this fails, surgery may help.
trigger fingerLocking of 1 or several
fingers in a bent position due to inflam-
mation of the sheath enclosing the tendon
of the affected finger. The finger is usually
tender at the base and slightly swollen
over the tendon. Treatment involves
local injection of a corticosteroid drug
or, if this is unsuccessful, surgery.
triglycerideA type of simple fat (see
fats and oils) made up of a molecule of
glyceroland 3 molecules of fatty acids.
Triglycerides are the main type of fat
found in stores of body fat.
trimeprazineAlso called alimemazine.
An antihistamine drugused to relieve
itching in allergic conditions, and as a
premedicationin children. Side effects
are typical of antihistamines.
trimesterA period of 3 months; human
pregnancyis conventionally divided into
3 trimesters.
trimethoprimAn antibacterial drug used
to treat a range of infections, most com-
monly those of the urinary tract. Possible
side effects include rash, itching, nausea,
vomiting, diarrhoea, and a sore tongue.
trimipramineA tricyclic antidepressant
drugused to treat depressionaccompa-
nied by anxietyor insomnia. Possible side
effects include dry mouth, blurred vision,
dizziness, constipation, and nausea.
triple vaccineSee DPT vaccination.triprolidineAn antihistamine drug that
is used to treat allergy, as an ingredient
of cough and cold remedies, and to
treat or prevent allergic reactions to
certain foods or blood transfusions. Pos-
sible side effects of triprolidine include
dry mouth, dizziness, difficulty in pass-
ing urine, and hyperactivity.
trismusInvoluntary contraction of the
jaw muscles, which causes the mouth to
become tightly closed. Commonly known
as lockjaw, it may occur as a symptom
of tetanus, tonsillitis, mumps, or acute
ulcerative gingivitisand other dental
problems affecting the back teeth. Treat-
ment is of the underlying cause.
trisomyThe presence of an extra chro-
mosomewithin a person’s cells, making
3 of a particular chromosome instead of
the usual 2. A fault during meiosisto
form egg or sperm cells leaves an egg or
sperm with an extra chromosome. When
the egg or sperm takes part in fertiliza-
tion, the resulting embryo inherits an
extra chromosome in each of its cells.
The most common trisomy is of
chromosome 21 (Down’s syndrome).
Trisomy 18 (Edward’s syndrome) and
trisomy 13 (Patau’s syndrome) are less
common; trisomy 8 and trisomy 22 are
very rare. Partial trisomy, with only part
of a chromosome in triplicate, also
occurs. Full trisomies cause abnorma-
lities such as skeletal and heart defects
and learning difficulties. Except in
Down’s syndrome, babies usually die in
early infancy. The effects of partial tri-
somies depend on the amount of extra
chromosomal material present.
Diagnosis is made by chromosome
analysisof cells, which may be obtained
from the fetus by amniocentesisor after
the birth. There is no specific treatment.
Parents of an affected child should seek
genetic counselling.
trisomy 21 syndromeAnother name
for Down’s syndrome.
trochlear nerveThe 4th cranial nerve.
The 2 trochlear nerves arise in the
brainstem, 1 on each side of the mid-
brain, and enter the eye sockets
through gaps in the skull bones. Each
trochlear nerve controls 1 of the 2 sup-
erior oblique muscles, which rotate the
eyes downwards and outwards.TRIFLUOPERAZINE TROCHLEAR NERVET