an early feature of cerebral palsy. It occurs
in disorders of the spinal cord, such as
Werdnig–Hoffman disease, and in some
children who have muscular dystrophy.
hypovitaminosis Any condition that re-
sults from insufficiency of 1 or more
vitamins.Hypovitaminosis may be due to
an inadequate dietary intake or a diges-
tive disorder that causes malabsorption.
hypovolaemiaAn abnormally low vol-
ume of blood in the circulation, usually
following blood loss due to injury, inter-
nal bleeding, or surgery. It may also be
due to loss of fluid from diarrhoeaand
vomiting. Untreated, it can lead to shock.
hypoxiaAn inadequate supply of oxy-
gento the tissues. Temporary hypoxia
may result from strenuous exercise. More
serious causes include impaired breath-
ing (see respiratory failure), ischaemia,
and severe anaemia. A rare cause is carbon
monoxidepoisoning. Severe, prolonged
hypoxia may lead to tissue death.
Hypoxia in muscles forces the muscle
cells to produce energy anaerobically,
which can lead to cramps. Hypoxia in
heart muscle may cause angina pectoris.
Hypoxia of the brain causes confusion,
dizziness, and incoordination, causing
unconsciousness and death if persistent.
Hypoxia can be assessed by using an
oximeterto measure the oxygen concen-
tration of blood in the tissues. Severe
hypoxia may require oxygen therapyor
artificial ventilation.
hysterectomySurgical removal of the
uterus. It is performed in order to treatHYSTERECTOMYfibroids, and cancer of the uterus (see
uterus, cancer of) or cervix (see cervix,
cancer of). It may also be performed to
relieve heavy menstrual bleeding or
endometriosis,and to remove a pro-
lapsed uterus (see uterus, prolapse of).
The most common type is a total hys-
terectomy, in which the uterus and
cervix are removed. Occasionally, the
fallopian tubes and ovaries are removed
as well. For cervical cancer, a radical
hysterectomy is performed, in which the
uterus, cervix and pelvic lymph nodes
are removed. Hysterectomy may be per-
formed through the vagina or through
an incision in the abdomen.
hysteriaAn old-fashioned term encom-
passing a wide range of physical or
mental symptoms attributed to mental
stress. Symptoms formerly grouped un-
der this term are now included in the
more specific diagnostic categories of
conversion disorder; somatization disor-
der; dissociative disorders; and factitious
disorders. The term is still used loosely
to describe irrational behaviour.
hysterosalpingographyAn X-ray pro-
cedure in which a dye (radiopaque
contrast medium) is introduced into the
cavity of the uterusvia the cervixto
make the uterus and fallopian tubesvisi-
ble on X-rays. Hysterosalpingography is
used to investigate infertility.
hysteroscopyA technique that uses a
hysteroscope (see endoscope)to diag-
nose disorders, such as uterine polyps,
inside the uterusand fallopian tubes.
Hysteroscopy can be performed under
local anaesthesia. Minor surgery, such
as the removal of fibroids, may also be
carried out through the hysteroscope.HYPOVITAMINOSIS HYSTEROSCOPYH
Fallopian tube Area to be removedUterusCervixVaginaTOTAL HYSTERECTOMYOvary
SITE OF
INCISION