Clinically isolated syndrome (CIS) is a first episode of neurological symptoms that lasts for at least 24 hours. Although some people never go on to experience further neurological symptoms, in others CIS can be the first sign of what may later turn out to be multiple sclerosis.
CIS is caused by damage to the covering of nerves in the central nervous system (CNS). Damage may occur in just one area of the brain or spinal cord (monofocal) resulting in a single symptom, such as optic neuritis which affects the eyes, or it may occur in several places (multifocal), which can lead to more symptoms, for example dizziness and bladder problems.
Not everyone who experiences CIS goes on to develop MS, figures vary from 1 in 5 people up to 4 in 5, so it is possible that you may never have any further symptoms. It's difficult to predict who will go on to have further episodes, but MRI scans can give a good idea of your risk of going on to develop MS. The more areas of damage seen on an MRI scan at the time of the CIS, the higher your risk of developing MS in the future.
Studies have shown that early treatment of CIS with disease modifying drugs can delay a second episode if you're at high risk of developing MS.
What is clinically isolated sydrome?
Clinically isolated syndrome (CIS) is the term used to describe your first episode of neurological symptoms that last for at least 24 hours and isn't caused by anything else - such as a fever or infection. CIS can be the first sign of what may subsequently turn out to be multiple sclerosis. You may never go on to experience further symptoms, but if an MRI scan shows several areas of damage (lesions) to your brain and/or spinal cord that are similar to those seen in MS then your chances of having further episodes, and ultimately a diagnosis of MS, are higher.
What causes CIS?
CIS is caused by inflammation and damage to myelin, the protective fatty substance that surrounds nerve cells in your brain and spinal cord (the central nervous system). This damage (called demyelination) disrupts the way nerve messages are carried to and from the brain and results in the symptoms you experience. The reasons why this happens aren't known yet.
How is CIS diagnosed?
A neurologist makes the diagnosis of clinically isolated syndrome. There's no one examination or test that can be used to diagnose CIS and the process involves ruling out other possible causes for your symptoms. Your medical history and a clinical examination are also important.
Sometimes an earlier episode of symptoms, such as numbness can prove significant as it could suggest a previous episode of neurological symptoms which you may not have thought much of at the time. Evidence of a previous episode could lead to a diagnosis of MS.
There are a number of simple tests that a neurologist can carry out that can suggest, or rule out, a cause for your symptoms. These include checks on your movement, coordination, vision, balance, reflexes and other functions of the senses. Information from these tests can determine whether you might have CIS and where in your central nervous system damage has occurred.
At the moment there is no blood test that can be used to diagnose either MS or CIS. However, blood tests might be carried out to identify, or rule out, other potential causes for your symptoms.
The most common test used is a scan of the brain and/or spinal cord using MRI. MRI can detect the tiny scars or lesions caused by demyelination which show up as little white patches on the scan image. Sometimes a dye called gadolinium is injected into a vein before your scan as it can help the radiologist and neurologist distinguish between active areas of inflammation and any older areas of scarring that might exist.
The areas where damage is most frequently seen in CIS are the optic nerve, the spinal cord, and the brainstem.
What are the symptoms I might experience
The symptoms you experience will depend on where in the brain or spinal cord damage has occurred. Common symptoms experienced by someone with CIS include:
Optic neuritis is caused by damage to the optic nerve which transmits images from the retina at the back of the eye to the brain. It can occur suddenly or over a period of hours. Optic neuritis commonly causes blind spots or areas of poor vision surrounded by an area of normal vision. Your colour vision can also be severely affected and you may experience pain, particularly during eye movement.
Optic neuritis is a condition in its own right and not everyone who experiences optic neuritis goes on to develop other symptoms of MS.
Transverse myelitis occurs when there is damage affecting the spinal cord. The onset of symptoms may be sudden - developing over one to two hours, or more gradual - over one to two weeks. The area of the spinal cord which is damaged will determine what symptoms you experience and which parts of your body are affected. Common symptoms include muscle weakness, abnormal sensations in the toes and feet such as numbness or tingling, and bladder or bowel problems.
Transverse myelitis can also be a condition in its own right and in most cases a person only has a single episode.
Lhermitte's sign (sometimes referred to as barber's chair syndrome) is a sudden sensation resembling an electric shock that passes down the back of your neck and into your spinal column and can radiate out to your fingers and toes. It is usually triggered by flexing your neck - bending your head down, chin towards chest - and is associated with lesions at the top of the spinal cord.
Brainstem syndrome occurs when there is damage to the nerves in the brainstem - the area at the base of the brain where it connects to the spinal cord. The brainstem controls basic functions such as your breathing, heart rate and blood pressure. Symptoms of brainstem syndrome include dizziness or vertigo, nausea, vomiting and double vision, but symptoms vary depending on the specific area affected.
How is CIS treated?
Many CIS episodes are mild and resolve on their own over a period of weeks. However when symptoms are more severe, for example visual loss and pain in optic neuritis, or vertigo where there is a brainstem lesion, you may be prescribed high dose steroids. These are given either as a pill or through a drip in hospital, but only for a few days. Steroids can speed up your recovery - however, your level of recovery will be the same whether you have steroid treatment or not.
Where necessary, you may also be prescribed treatments for specific symptoms.
If you're at a higher risk of developing MS, your neurologist may give you the choice of taking a disease modifying drug (DMD).
What is the risk of developing MS following CIS?
To make a diagnosis of MS, the neurologist is looking for evidence you have two or more areas of damaged myelin in different parts of your brain and/or spinal cord. This damage will need to have occurred at different points in time.
Clinically isolated syndrome refers to a single point in time – it is just one episode of neurological symptoms. If you've experienced a multifocal clinically isolated syndrome, although damage may have occurred in more than one place, it has still only happened at one point in time, so you wouldn't be given a diagnosis of MS if there is no evidence of a previous episode.
The evidence of damage to your myelin may be seen clinically - as an episode of neurological symptoms lasting more than 24 hours - or on an MRI scan. A diagnosis of MS may be made on the basis of one clinical episode if an MRI scan shows evidence of a previous attack.
There's no single test that can definitively determine whether you'll go on to develop MS or not after experiencing CIS. Many factors have been investigated to see if they can better determine your risk, including:
- your age
- your ethnicity
- where you live
- the number, location and size of lesions seen on an MRI scan
- levels of various different proteins in your serum, blood or the fluid surrounding the spinal cord (CSF)
- vitamin D levels
- the symptoms you experienced during your CIS.
Of these, MRI findings are the most useful tool to determine your risk of developing MS. Other strong predictors are being older at the time of your CIS, or if oligoclonal bands are detected in the cerebrospinal fluid.
The diagnostic criteria for MS were updated in 2017. These changes have made them more sensitive and led to less diagnostic uncertainty, which means that more people are being diagnosed earlier with MS and fewer people are being given a diagnosis of CIS.
Are there lifestyle changes I can make that might help reduce the risk?
There is evidence that smokers with CIS have a higher risk of developing MS than non-smokers. So the best advice is to stop smoking if you are a smoker.
Some studies suggest that low levels of vitamin D can increase your risk of converting from CIS to MS. If you have low levels of vitamin D you may want to consider taking a vitamin D supplement, although it's not yet clear whether taking supplements is effective.
Living with uncertainty
If you have experienced CIS, living with the uncertainty of whether you will go on to develop MS or not can cause anxiety, fear, confusion or even anger. Research has shown that there is an increased risk of mild to moderate depression and anxiety in those with CIS. It can feel frustrating that health professionals can't say what you might expect to happen in the short or longer term.
However, having access to reliable information so you are fully informed about the condition and can make the right decisions for you is important. In some areas MS nurses are available to support people diagnosed with CIS. If this isn't the case for you, it's important to contact your GP or neurologist if you experience new symptoms that could potentially lead to a diagnosis of MS.
Radiologically isolated sydrome (RIS)
A neurologist can also make a diagnosis of radiologically isolated syndrome (RIS). This is when someone who has not had any MS symptoms has had an MRI scan for another reason (for example following a trauma or if you experience migraines) and brain or spinal cord lesions compatible with MS have shown up in that scan.
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