What is clinically isolated syndrome (CIS)?
Clinically isolated syndrome (CIS) is an episode of neurologic symptoms. CIS involves demyelination in your central nervous system. That means you’ve lost some myelin, the coating that protects nerve cells.
To be classified as CIS, the episode must last at least 24 hours. It can’t be associated with fever, infection, or other illness.
CIS, by its very name, indicates that you’ve had an isolated incident. It doesn’t mean you should expect more or that you’ll definitely develop multiple sclerosis (MS). However, CIS is sometimes the first clinical episode of MS.
Continue reading to learn more about the connection between CIS and MS, how the distinction is made, and what your next steps should be.
With CIS, you don’t know if it’ll ever happen again. Conversely, MS is a lifelong disease without a cure, though it can be managed.
Some symptoms of CIS are:
- Optic neuritis. This is a condition in which your optic nerve is damaged. This can cause poor vision, blind spots, and double vision. You might also experience eye pain.
- Transverse myelitis. This condition involves damage to your spinal cord. Symptoms can include muscle weakness, numbness and tingling, or bladder and bowel issues.
- Lhermitte’s sign. Also known as barber chair phenomenon, this condition is caused by a lesion on the upper part of your spinal cord. An electric shock-like feeling goes from the back of your neck to your spinal column. This may happen when you bend your neck downward.
CIS can cause difficulties with:
- balance and coordination
- dizziness and shakiness
- muscle stiffness or spasticity
- sexual function
- walking
Both CIS and MS involve damage to the myelin sheath. Inflammation causes the formation of lesions. These interrupt signals between your brain and the rest of the body.
Symptoms depend on the location of the lesions. They can range from barely detectable to disabling. It’s hard to distinguish CIS from MS based on symptoms alone.
The difference between the two conditions may be detectable through an MRI. If there’s evidence of only one episode, you probably have CIS. If images show multiple lesions and evidence of other episodes separated by space and time, you may have MS.
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