Myelitis refers to a disorder associated with acute
or chronic inflammation which occurs within the spinal cord and compromises the
function of nerve fibers within the gray and/or the white matter of the spinal
cord. The specific cause of myelitis is not always
known at the time of the initial clinical presentation. Myelitis usually
involves a specific region or segment of the spinal cord. It may extend all the
way across the spinal cord at the involved segment, a condition referred to as
transverse myelitis. If it does not involve the whole segment of the spinal
cord it may be referred to as focal myelitis or incomplete transverse myelitis.
myelitis is characterized by the development of inflammation across both sides
of one level, or segment, of the spinal cord. The segment of the spinal cord at
which the damage occurs determines which parts of the body are affected. Damage at one segment will affect
function at that segment and segments below it. In people with transverse
myelitis, inflammation usually occurs at the thoracic (upper back) level,
causing problems with leg movement and bowel and bladder control, which require
signals from the lower segments of the spinal cord. Transverse myelitis can occur anywhere along the course of
the spinal cord.
Transverse myelitis occurs in adults and children, in both
genders, and in all races. No familial predisposition is apparent. A peak in
incidence rates (the number of new cases per year) appears to occur between 10
and 19 years and 30 and 39 years. Although only a few studies have examined
incidence rates, it is estimated that about 1,400 new cases of transverse
myelitis are diagnosed each year in the United States, and approximately 33,000
Americans have some type of disability resulting from the disorder.