Each case of MS displays one of several patterns of
presentation and subsequent course. Most commonly,
MS first manifests itself as a series of attacks
followed by complete or partial remissions as
symptoms mysteriously lessen, only to return later
after a period of stability. This is called
relapsing-remitting (RR) MS. Primary-progressive (PP)
MS is characterized by a gradual clinical decline
with no distinct remissions, although there may be
temporary plateaus or minor relief from symptoms.
Secondary-progressive (SP) MS begins with a
relapsing-remitting course followed by a later
primary-progressive course. Rarely, patients may
have a progressive-relapsing (PR) course in which
the disease takes a progressive path punctuated by
acute attacks. PP, SP, and PR are sometimes lumped
together and called chronic progressive MS.
In addition, twenty percent of the MS population
has a benign form of the disease in which symptoms
show little or no progression after the initial
attack; these patients remain fully functional. A
few patients experience malignant MS, defined as a
swift and relentless decline resulting in
significant disability or even death shortly after
disease onset. However, MS is very rarely fatal and
most people with MS have a fairly normal life
expectancy.
Studies throughout the world are causing
investigators to redefine the natural course of the
disease. These studies use a technique called
magnetic resonance imaging (MRI) to visualize
the evolution of MS lesions in the white matter of
the brain. Bright spots on a T2 MRI scan indicate
the presence of lesions, but do not provide
information about when they developed.
Because investigators speculate that the
breakdown of the blood/brain barrier is the first
step in the development of MS lesions, it is
important to distinguish new lesions from old. To do
this, physicians give patients injections of
gadolinium, a chemical contrast agent that
normally does not cross the blood/brain barrier,
before performing a scan. On this type of scan,
called T1, the appearance of bright areas indicates
periods of recent disease activity (when gadolinium
is able to cross the barrier). The ability to
estimate the age of lesions through MRI has allowed
investigators to show that, in some patients,
lesions occur frequently throughout the course of
the disease even when no symptoms are present.
While there is no good evidence that daily stress or
trauma affects the course of MS, there is data on
the influence of pregnancy. Since MS generally
strikes during childbearing years, a common concern
among women with the disease is whether or not to
have a baby. Studies on the subject have shown that
MS has no adverse effects on the course of pregnancy,
labor, or delivery; in fact symptoms often stabilize
or remit during pregnancy. This temporary
improvement is thought to relate to changes in a
woman's immune system that allow her body to carry a
baby: because every fetus has genetic material from
the father as well as the mother, the mother's body
should identify the growing fetus as foreign tissue
and try to reject it in much the same way the body
seeks to reject a transplanted organ. To prevent
this from happening, a natural process takes place
to suppress the mother's immune system in the uterus
during pregnancy.
However, women with MS who are considering
pregnancy need to be aware that certain drugs used
to treat MS should be avoided during pregnancy and
while breast feeding. These drugs can cause birth
defects and can be passed to the fetus via blood and
to an infant via breast milk. Among them are
prednisone, corticotropin, azathioprine,
cyclophosphamide, diazepam, phenytoin, carbamazepine,
and baclofen.
Unfortunately, between 20 and 40 percent of women
with MS do have a relapse in the three months
following delivery. However, there is no evidence
that pregnancy and childbirth affect the overall
course of the disease one way or the other. Also,
while MS is not in itself a reason to avoid
pregnancy and poses no significant risks to the
fetus, physical limitations can make child care more
difficult. It is therefore important that MS
patients planning families discuss these issues with
both their partner and physician.
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