Multiple sclerosis (MS) is the most common immune-mediated inflammatory demyelinating disease of the central nervous system. The onset and phenotypes of MS will be examined here. The symptoms and clinical signs of MS are examined elsewhere.
Onset of Multiple Sclerosis (MS)
The typical patient presents as a young adult with one or more clinically distinct episodes of central nervous system dysfunction (i.e., a clinically isolated syndrome [CIS] with at least partial resolution).
- Clinically isolated syndrome – A CIS is the first clinical episode suggestive of MS, or it may be the first attack of MS if the evaluation confirms that the patient meets the diagnostic criteria for MS. Typical presentations include unilateral optic neuritis, painless diplopia, a brainstem or cerebellar syndrome, or partial transverse myelitis.
- Prodromal multiple sclerosis – Prodromal MS is a relatively new concept that is not fully defined or characterized, but there is evidence that early nonspecific symptoms and clinical signs precede the typical symptoms and signs of MS.
- Radiologically isolated syndrome (RIS) – Some cases of MS may be heralded by an RIS, defined by incidental findings on MRI of the brain or spinal cord that are highly suggestive of MS in a patient lacking a history, symptoms, or signs of MS.
Main Phenotypes of Multiple Sclerosis
The main phenotypes of MS are those of relapsing and progressive disease. The type and course of MS are further classified into several clinical phenotypes or subtypes as follows:
- Relapsing-remitting multiple sclerosis – This phenotype is characterized by clearly defined relapses with full recovery or with sequelae and residual deficit upon recovery. There is no or minimal progression of the disease between disease relapses. This type of MS accounts for approximately 85 to 90 percent of cases of MS at onset. However, many patients with relapsing MS eventually enter a secondary progressive phase.
- Secondary progressive multiple sclerosis – This phenotype is characterized by an initial relapsing course of MS, followed by progression with or without occasional relapses, minor remissions, and plateaus. Some studies suggest that secondary progressive MS eventually develops in most patients with relapsing MS and is the stage at which patients accumulate the greatest number of neurological impairments.
- Primary progressive multiple sclerosis – This phenotype is characterized by progression of the disease from onset with occasional plateaus and temporary minor improvements allowed ; acute relapses may also occur. This type accounts for about 10 percent of adult cases at disease onset.
Progression of Disability
The progression of disability due to MS is highly variable. Increasing evidence suggests that disability progression occurs primarily due to clinically silent neurodegeneration, independent of relapse activity. At the extremes of the severity spectrum, there are benign and malignant forms of MS, but their determination is always retrospective and must be made with caution.
Predicting Outcomes
There are a variety of possible prognostic indicators in MS. However, none are completely reliable, and our ability to accurately predict outcomes for each patient with MS is limited. The development of a progressive course of MS could be the most unfavorable factor influencing prognosis.
Source: UpToDate