Babinski’s signA reflex movement in
which the big toe bends upwards when
the outer edge of the sole of the foot is
scratched. In adults, Babinski’s sign in-
dicates damage or disease of the brain
or the spinal cord. In babies, Babinski’s
sign is a normal reflex.
baby bluesA common name for a mild
form of depression that sometimes
occurs in women after childbirth. Baby
blues almost always disappears without
treatment but can occasionally develop
into a more serious depressive illness
(see postnatal depression).
bacilliRod-shaped bacteria. The singu-
lar term is bacillus.
backThe area between the shoulders
and the buttocks. The back is supported
by the spinal column (see spine), which
is bound together by ligaments and
supported by muscles that also control
posture and movement. Disorders that
affect the bones, muscles, ligaments,
tendons, nerves, and joints in the spine
may cause back pain. (See also spine,
disorders of.)
back painPain affecting the back, often
restricting movement. The pain usually
lasts for only a week or so but can recur
in some people. Rarely, persistent back
pain causes long-term disability.
Back pain is usually caused by minor
damage to the ligaments and muscles
in the back. The lower back is especially
vulnerable to these problems because it
supports most of the body’s weight and
is under continual stress from move-
ments such as bending, twisting, and
stretching. Less commonly, lower back
pain may result from an underlying dis-
order such as a prolapsed intervertebral
disc (see disc prolapse)in the spine.
In most cases, back pain can be trea-
ted with over-the-counter painkillers
(see analgesic drugs) such as aspirin
and related drugs,nonsteroidal anti-
B
inflammatory drugs, or muscle-relaxant
drugs. If the pain persists, a heat pad, a
wrapped hot-water bottle or, sometimes,
an ice-pack, may provide additional
relief. Generally, it is advisable to
remain as active as the pain permits.
People whose pain worsens or is still
too severe to allow normal movement
after several days should consult a doc-
tor for medical tests.
Investigations for back pain, such as
X-rays, CT scanning, or MRI, sometimes
reveal abnormalities, such as disc pro-
lapse, that require surgical treatment and
can be treated by a microdiscectomy.
Other treatments for back pain include
acupuncture, spinal injection, exercise,
or spinal manipulation.
baclofenA muscle-relaxant drugthat is
used to relieve muscle spasm and stiff-
ness due to brain or spinal cord injury,
stroke, or neurological disorders such
as multiple sclerosis. Adverse effects of
baclofen include drowsiness and muscle
weakness; these side effects can be lim-
ited, however, by increasing the dose of
the drug gradually.
bacteraemiaThe presence of bacteriain
the bloodstream. Bacteraemia occurs
briefly after many minor surgical oper-
ations and dental treatment. The immune
systemusually prevents the bacteria
from multiplying and causing damage.
However, in people who have abnormal
heart valves, the bacteria may settle on
the valve and cause endocarditis. If the
immune system is damaged or sup-
pressed, septicaemia(an infection of the
blood) may develop.
bacteriaSingle-celled microorganisms
that are invisible to the naked eye. The
singular form of the term is bacterium.
Abundant in the air, soil, and water,
most bacteria are harmless to humans.
Some bacteria, such as those that live
in the intestine, are beneficial and help
to break down food for digestion. Bacteria
that cause disease are known as patho-
gens and are classified by shape into
3 main groups: cocci (spherical); bacilli
(rod-shaped); and spirochaetes or spir-
illa (spiral-shaped). Many bacteria have
whip-like threads called flagella, which
enable them to move in fluids, and pili,
which anchor them to other cells.BABINSKI’S SIGN BACTERIA
B