Clinically isolated syndrome (CIS) is a first episode of neurologic symptoms caused by demyelination and inflammation in the central nervous system. These neurologic symptoms, similar to those of multiple sclerosis (MS), must last at least 24 hours with no accompanying fever or infection for CIS to be diagnosed. In people who have experienced CIS, MRI scans may show a lesion on the brain or spinal cord like those seen in MS. The primary difference between CIS and MS is that MS features multiple lesions or multiple episodes of neurological symptoms. An episode of CIS is followed by total or partial recovery, and some people who experience CIS once may never have another occurance of symptoms.
The International Advisory Committee on Clinical Trials of MS considers CIS one of four main MS disease courses. CIS becomes definite MS when a second occurrence of symptoms or a worsening of lesions happens — or both.
Episodes of clinically isolated syndrome may be described as either monofocal or multifocal. In a monofocal episode, there is one neurologic symptom (for example, optic neuritis or numbness) or a sign (such as a test result showing oligoclonal bands in cerebrospinal fluid) that is caused by one lesion in the central nervous system. In a multifocal episode, there is more than one symptom or test result showing signs of more than one lesion.
The process of diagnosing CIS and MS are similar. One key difference is the singular nature of CIS. If more than one area of lesions is found and more than one neurologic event occurs, the diagnosis is MS. An MRI scan is used to confirm the presence, number, and location of lesions on a person’s brain or spinal cord.
You may be at a higher risk of developing MS if your CIS includes lesions on the brain similar to those seen in people living with MS. If this is the case, there is a 60 percent to 80 percent chance that you will develop MS within the next few years. In other words, you are more likely to experience a recurrence of neurologic symptoms or have follow-up MRIs which discover more lesions.
Your risk of developing MS is lower if there are no brain lesions detected by MRI during your episode of CIS. People who have CIS without brain lesions have approximately a 20 percent chance of developing MS over the next several years.
Some CIS symptoms resolve by themselves, without treatment. Whether or not your neurologist recommends starting treatment, and which treatment they recommend, depends on your risk level for a second occurrence of neurological symptoms.
If your CIS is determined to be low risk for a recurrance, it may be treated with short-term corticosteroids. Taken long-term, corticosteroids can cause serious side effects like cataracts, osteoporosis, diabetes, and Cushing’s syndrome.
If your doctor determines you’re at a high risk for developing MS, evidence suggests treating CIS with disease-modifying drugs may delay progression and prevent or slow demyelination. Several disease-modifying therapies (DMTs) are approved by the U.S. Food and Drug Administration (FDA) to treat CIS, as well as types of MS. DMTs recommended for people with high-risk CIS may include:
In 2010, the diagnostic criteria for MS were amended. This update recognized CIS as the first clinical event before MS, rather than as a unique condition. These updated criteria allow for the earliest possible diagnosis and initiation of treatment. There are several reasons early treatment is often encouraged.
Ample data support the theory that early treatment provides the best outcomes regarding symptom management, nerve damage, and disability. When it comes to CIS, early treatment appears to prevent or delay a second neurologic event — after which a CIS diagnosis becomes MS — and future relapses.
An analysis of four phase III clinical trials on disease-modifying therapies for people with CIS found 80 percent of those that recieved the placebo rather than the DMTs converted to MS. After 15 to 20 years, one-third of those participants showed little physical disability and had reported fewer relapses. As many as half had developed secondary progressive (SPMS) with progressively worsening disability. These clinical trials also found that the more lesions a person had earlier in their disease course, the higher the likelihood their MS would progress to disability after 20 years. A 2014 clinical trial of Aubagio (Teriflunomide) on people with CIS further supported the importance of treatment to delay additional relapses as early as possible in the disease process.
Evidence suggests that more damage than previously thought occurs during the first episode of neurological symtpoms (CIS) and early-stage MS. In fact, disease activity seems to make an impact even before the first symptoms present. In the early stages of MS, people exhibit new MRI activity seven to 10 times more frequently than noticeable physical symptoms. Signs of new MRI activity include brain atrophy, lesions and abnormalities in both gray and white matter, inflammation, and nerve damage.
Currently available disease-modifying therapies mostly address inflammation. Inflammation and demyelination are interrelated with MS and occur at varying rates throughout the course of the disease.
The damaging effects of the early symptoms of CIS and MS have been linked to long-term disease outcomes, including disability. Treatment is best begun during the early relapsing phase. This can slow the growth and worsening of lesions and decrease relapse frequency.
You may never go on to experience a second occurrence of CIS symptoms, but it is very important to consult your doctor to evaluate your risk of developing MS. An MRI scan can help doctors to see whether there are lesions in your central nervous system that resemble MS.
Studies show that inflammation and damage to the central nervous system are related to CIS and occur throughout the MS disease process. Careful monitoring with your doctor and starting the right treatment as early as possible may minimize inflammation and the resulting nerve damage.
Mounting evidence shows that early treatment (as well as earlier diagnosis) yields the best long-term outcomes when it comes to MS. Diagnosing and treating relapsing types of MS before a person begins to accumulate signs of disability is important. Early treatment presents the best possible prognosis in both the short and long term.
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