Webster's New World Medical Dictionary

spider telangiectasia
See 
spider vein.
spider vein
A group of widened veins that can be
seen through the surface of the skin. The wheel-
and-spokes shape of the veins resembles a spider.
Also known as spider telangiectasia.
spina bifida
A major birth defect and a type of
neural tube defect that involves an opening in the
vertebral column caused by the failure of the neural
tube to close properly during embryonic develop-
ment. (The neural tube is the structure in the devel-
oping embryo that gives rise to the brain and spinal
cord.) Because of the defect in the spine, part of the
spinal cord is exposed and protrudes as a
meningomyelocele. People with spina bifida often
have neurological deficits below the level of the
lesion and can suffer from bladder and bowel
incontinence, limited mobility (due to paralysis of
the legs), and learning problems. The risk of spina
bifida varies according to country, ethnic group,
and socioeconomic status. In the US as a whole,
spina bifida occurs in 1 in every 1,000 to 2,000
births. The risk of spina bifida and other neural
tube defects, such as anencephaly, can be signifi-
cantly decreased if women take ample folic acid
before conception and during pregnancy.
spina bifida cystica
See 
meningomyelocele.
spina bifida occulta
A bony defect in the verte-
bral column that causes a cleft in that column. The
cleft remains covered by skin. Treatment is usually
not required.
spinal column
See 
vertebral column.
spinal cord
The major column of nerve tissue
that is connected to the brain and lies within the ver-
tebral canal and from which the spinal nerves
emerge. Thirty-one pairs of spinal nerves originate
in the spinal cord: 8 cervical, 12 thoracic, 5 lumbar,
5 sacral, and 1 coccygeal. The spinal cord and the
brain constitute the central nervous system. The
spinal cord consists of nerve fibers that transmit
impulses to and from the brain. Like the brain, the
spinal cord is covered by three connective-tissue
envelopes called the meninges. The space between
the outer and middle envelopes is filled with cere-
brospinal fluid (CSF), a clear colorless fluid that
cushions the spinal cord against jarring shock. Also
known simply as the cord.
spinal fusion
A surgical procedure in which two
or more of the vertebrae in the spine are united
together so that motion no longer occurs between
them. Spinal fusion may be done to treat a number
of conditions, including scoliosis, deformity, frac-
ture, and disc disease. Bone grafts are usually
placed around the section of the spine to be fused.
The body then heals the grafts over several months,
which joins the vertebrae together. The bone for the
graft may be taken from another bone in the patient
(autograft) or from a bone bank (allograft). Metal
rods, plates, screws, and cages may also be used as