Webster's New World Medical Dictionary

schizoid
Having symptoms similar to those of
schizophrenia.
schizophrenia
One of several brain diseases
whose symptoms may include loss of personality
(flat affect), agitation, catatonia, confusion, psy-
chosis, unusual behavior, and social withdrawal.
The illness usually begins in early adulthood. The
cause of schizophrenia is not known, but there
appear to be both genetic (inherited) and environ-
mental components to the disease. Schizophrenia is
not caused by abuse or poor parenting practices.
Treatment involves use of neuroleptic medication
and supportive interpersonal therapy. The progno-
sis is fairly good, with two-thirds of those diagnosed
recovering significantly.
schizophrenia, childhood
The onset of schizo-
phrenia before adulthood. This condition is very
rare in young children, but it occurs with more fre-
quency in the teenage years. Autism was once
known as childhood schizophrenia, but it is a com-
pletely different disorder. See also 
autism; child-
hood disintegrative disorder; developmental
disorder; schizophrenia.
schizotypal personality disorder
A personal-
ity type that is characterized by unusual patterns of
speech and behavior and by social withdrawal. See
also 
Asperger syndrome.
Schmorl’s node
An upward and downward pro-
trusion (pushing into) of a spinal disk’s soft tissue
into the bony tissue of the adjacent vertebrae.
Schmorl’s nodes, which are common, especially
with minor degeneration of the aging spine, are
detectable via X-ray as spine abnormalities.
Schmorl’s nodes are most common in the middle
and lower spine. Schmorl’s nodes usually cause no
symptoms, but they reflect that “wear and tear” of
the spine has occurred over time.
Schwann cell
An insulating cell found in the
peripheral nervous system that surrounds nerve
fibers (axons). Schwann cells form the myelin
sheath that facilitates the conduction of impulses
along the nerve. See also 
myelin; peripheral nerv-
ous system.
schwannoma
A tumor that arises in the Schwann
cells, or myelin sheath, of the peripheral nerves.
Schwannomas are usually benign. Acoustic neuro-
mas of the eighth cranial nerve are the most com-
mon schwannomas. Also known as neurilemmoma.
sciatic nerve
The largest nerve in the body,
which begins from nerve roots in the lumbar spinal
cord in the low back (sacrum) and extends through
the buttock area, sending nerve endings down
through the legs and knees. See also 
sciatica.
sciatica
Pain that results from irritation of the
sciatic nerve and typically radiates from the buttock
to the back of the thigh. Although sciatica can result
from a herniated disc pressing directly on the nerve,
any cause of irritation or inflammation of this nerve
can reproduce the painful symptoms of sciatica.
Diagnosis is made via observation of symptoms,
physical examination and nerve tests, and some-
times X-ray or magnetic resonance imaging (MRI),
if a herniated disk is suspected. Treatment options
include avoiding movements that further irritate the
condition, use of medication, physical therapy, and
sometimes surgery.