Multiple sclerosis (MS)
is an autoimmune inflammatory disease of the central nervous system (CNS), which predominantly affects white matter, though gray matter involvement also occurs. It is a progressive neurodegenerative condition; early axonal loss has been identified.1
MS causes demyelination and scarring of myelin, resulting in plaques visible on MRI and in histopathologic specimens. The manifestations of the disease vary from an insidious progressive to a rapidly progressive and disabling illness that has a profound effect on physical function and quality of life.2
See Figure 32-1
The classification of MS is based on its variable clinical courses (see Table 32-1
). These courses are defined by periods of relapse, remission, and chronic progression.4
The etiology of MS is unknown, although it is hypothesized that a virus may precipitate an autoimmune response in a genetically susceptible individual with certain environmental exposures. MS has been called the disease of young adults because the highest rate of incidence is between the ages of 20 and 50 years. In fact, it is the most common nontraumatic cause of neurologic disability in young adults.5
Recent research suggests that low vitamin D levels, smoking, and Epstein-Barr virus infections are associated with increased risk of MS.6
There are more than 4,00,000 cases of MS in the United States,1
with women being affected at least three times as frequently as men. Whites are affected more frequently than any other racial group. The lifetime risk of MS in the general population is approximately 0.1%, but children of a parent with MS have a 3% risk, thus supporting genetic susceptibility theories. There have been many susceptibility loci identified through genetic studies in recent years.6
Epidemiologic studies report that MS is more prevalent in the colder northern latitudes, though there may be an attenuation in latitude gradient that suggests other environmental associative factors. In general, MS is more common in Europe, the United States, Canada, New Zealand, and Southern Australia than in more tropical regions. Moving to a warmer climate before the age of 15 years confers a lower risk of climate influence.
The course of MS is unpredictable even within each subtype. Cohort studies have provided broad prognostic factors. Younger age at onset, female gender, monosymptomatic presentation, complete relapse recovery, long interval between first and second relapses, few relapses, and a relapsing rather than a progressive course are factors associated with a better prognosis. In addition to
male gender, poorer prognosis is associated with age of onset over 40 years; initial presentation of motor, cerebellar, or sphincter symptoms or polysymptomatic presentation; frequent attacks in the first 5 years; and a short interval between attacks.6
Figure 32-1 ▪ Myelin destruction in multiple sclerosis. Asset provided by Anatomical Chart Co.
TABLE 32-1 FOUR CATEGORIES OF MULTIPLE SCLEROSIS (MS) BASED ON CLINICAL COURSE
Radiologically isolated syndrome (RIS)
Clinically Isolated Syndrome (CIS)
Relapsing-remitting MS (RRMS) (80% of all cases)
Incidental brain MRI findings suggestive of demyelinating disease in patients who had brain imaging for reasons other than the suspicion of MS.3
A single neurologic episode consistent with CNS inflammation or demyelination; may be monofocal or multifocal; examples include optic neuritis, transverse myelitis, and brainstem or cerebellar syndromes; a high risk of developing MS is present.
Characterized by recurrent attacks of neurological dysfunction which evolve over days to weeks and may be followed by complete, partial, or no recovery; there is no progression of symptoms between attacks; this pattern is often seen in the early course of the disease and is the most common form seen.
Secondary progressive MS (SPMS)
Gradual neurological deterioration with or without acute relapses, minor remissions, and plateaus in a patient who previously had RRMS.
Progressive-relapsing MS (PRMS)
From the onset, there is gradual progression of disability; unlike RRMS, there is continuing disease progression without stabilization of the disease
Primary progressive MS (PPMS)
A pattern of gradual neurological deterioration from the onset of symptoms, but with superimposed relapses noted.